dermatopathology ddx - md heromdhero.com/dermatopathology-ddx-morphology.pdf · the corni˚ed layer...
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See skin neoplasms section for mass, atypia, mitosis ddxSee nevus section for nevi ddx
Normal pigmentation
Fontana-Masson stain shows normal pigmentation at the basal cell layer.
Normal
Periodic acid–Schi� stain shows the presence of fungal hyphae within the corni�ed layer.
Dermatophytosis
Hyperkeratosis
SCC
hyperkeratosis, hypergranulosis, irregular epidermal hyperplasia, and a bandlike, predominantly lymphocytic in�ltrate that obscures the dermoepidermal junction. Melanophages are present in the dermal in�ltrate.
Lichen planus
Sebo
rrhe
ic K
erat
osis
parakeratotic burrow containing body parts of the mite of scabies. The dermal in�ammatory cell in�ltrate typically contains frequent eosinophils.
Scabies
neutrophilic aggregates underneath the corni�ed layer. Acantholytic keratinocytes may be seen in addition to neutrophils.
Subcorneal pustular dermatosis
Hyperkeratosis, hyperplasia, pseudohorn cyst
Seborrheic keratosis
Pityriasis rubra pilaris
Alternating layers of hyperkeratosis and parakeratosis in both vertical and horizontal patterns, psoriasiform epidermal hyperplasia, and mild super�cial perivascular in�ammation are seen.
high-power view shows alternating hyperkeratosis and parakeratosis with a normal granular layer.
Pityriasis rubra pilarisA
ctin
ic k
erat
osis
Verr
uca
Vulg
arisParakeratosis
focal parakeratosis with neutrophils and mild super�cial perivascular in�ammation
Dermatophytosis
Parakeratosis containing collections of neutrophils, vacuolar alteration of the basal cell layer, and patchy lichenoid and perivascular lymphocytic in�ammation are seen. Scattered necrotic keratinocytes and extravasated red cells are present.
Pityriasis lichenoides acuta
Histologic section shows parakeratosis with neutrophils, epidermal hyperplasiaand a dense bandlike in�ammatory cell in�ltrate that obscures the dermoepidermal junction
Secondary syphilis
sharply demarcated epidermal proliferation composed of keratinocytes with pale cytoplasm. Parakeratosis and neutrophils in the parakeratosis and among the clear cells are typical �ndings.
Clear cell acanthoma
papillomatous, parakeratosis, Hypergranulosispresence of koilocytes (vacuolated keratinocytes)dilated blood vessels in the papillary dermis are additional �ndings.
Verruca vulgaris
parakeratosis, hypogranulosis that spares the openings of the adnexal structuresBudding of the basal cells, keratinocytic atypia, and solar elastosis are present.
Actinic keratosis
exoendophytic neoplasm, central cup-shaped cratersurrounded by proliferation of large keratinocytes with abundant glassy cytoplasm and minimal cytologic atypia di�erentiates this form of squamous cell carcinoma from the conventional squamous cell carcinoma. Neutrophilic microabscesses may be seen at the base of the neoplasm.
Keratoacanthoma
con�uent parakeratosis and increased thickness of epidermis. The epidermis contains atypical keratinocytes with pleomorphic nuclei, dyskeratotic cells, and frequent mitotic �gures above the basal cell layer. The changes are con�ned to the epidermis, and therefore this lesion is considered a form of squamous cell carcinoma in situ.
Bowen disease
The epidermal proliferation shows tunnel-like invaginations �lled with parakeratosis.The neoplasm in�ltrates as bulbous expansions of the rete.
Verrucous carcinoma
Stratum cornea
Fontana-Masson stain shows loss of pigmentation at the basal cell layer
Vitiligo
thickening of the basement membrane
Cutaneous lupus erythematosus
granular positivity along the basement membrane of the epidermis and the adnexal epithelium. Positive �uorescence may be seen with immunoglobulin G (IgG) or IgM and C3
Cutaneous lupus erythematosus
Intraepidermal spongiosis and collections of eosinophils both within the epidermis and in the dermal in�ammatory cell in�ltrate are seen.
Incontinentia pigmenti
Eosinophil
abundant eosinophils within the spongiotic vesicle, which favors a diagnosis of contact dermatitis.
contact dermatitis.
hyperkeratosis with follicular plugging, atrophy of the epidermis, marked vacuolar alteration of the basal cell layer, and a thickened and smudged basement membrane. Perifollicular lymphocytic in�ltrate is present.
Cutaneous lupus erythematosus
Vacuolar alteration of the basal cell layer, epidermal atrophy, and a mild perivascular in�ammatory cell in�ltrate are seen.
Dermatomyositis
Epidermal atrophy
Acid-fast bacillus stain demonstrates the presence of acid-fast bacilli within the cytoplasm of some of the histiocytes.
Leprosy
Full-thickness epidermal necrosis with separation at the dermoepidermal junction is seen. The corni�ed layer is unaltered, attesting to the acute nature of the process, and there is only a minimal in�ammatory cell in�ltrate.
Toxic epidermal necrolysis
intraepidermal vesicle with prominent suprabasal acantholysis.
Pemphigus
Separations
subepidermal blister containing eosinophils and some neutrophils.
Bullous pemphigoid
separation at the dermoepidermal junction associated with aggregates of neutrophils, especially at the tips of the dermal papillae (papillary microabscesses).
Dermatitis herpetiformis SCC
Con�uent parakeratosis with collections of neutrophils, diminished granular layer, regular (psoriasiform) epidermal hyperplasia with thinning of suprapapillary plates, dilated blood vessels in the papillary dermis, and mild super�cial perivascular in�ammation are seen.
Psoriasis
Hyperplasia
Poro
ma
(Looks like hyperplasia)
Histologic section shows parakeratosis with neutrophils, epidermal hyperplasiaand a dense bandlike in�ammatory cell in�ltrate that obscures the dermoepidermal junction
Secondary syphilis
epidermal hyperplasia associated with suppurative and granulomatous in�ammation.
Blastomycosis
Hyperkeratosis, hyperplasia, pseudohorn cyst
Seborrheic keratosis
sharply demarcated epidermal proliferation composed of keratinocytes with pale cytoplasm. Parakeratosis and neutrophils in the parakeratosis and among the clear cells are typical �ndings.
Clear cell acanthoma
con�uent parakeratosis and increased thickness of epidermis. The epidermis contains atypical keratinocytes with pleomorphic nuclei, dyskeratotic cells, and frequent mitotic �gures above the basal cell layer. The changes are con�ned to the epidermis, and therefore this lesion is considered a form of squamous cell carcinoma in situ.
Bowen disease
papillomatous epidermal hyperplasia associated with prominent sebaceous lobules and poorly formed follicular units.
Nevus sebaceus
Vacuolar alteration of the basal cell layer is seen, above which there are necrotic keratinocytes.
Erythema multiforme
Basal vacuole
Vacuolar alteration of the basal cell layer is seen with scattered necrotic keratinocytes within the epidermis. Lymphocytes are present at the basal cell layer and extending into the epidermis, where they may surround the necrotic keratinocytes (satellite necrosis)
acute GVHD
Parakeratosis containing collections of neutrophils, vacuolar alteration of the basal cell layer, and patchy lichenoid and perivascular lymphocytic in�ammation are seen. Scattered necrotic keratinocytes and extravasated red cells are present.
Pityriasis lichenoides acuta
Necrotic keratinocytes in the epidermis, vacuolar alteration of the basal cell layer, and patchy lichenoid in�ammatory cell in�ltrate that obscures the dermoepidermal junction are seen. Histologic changes are similar to those seen erythema multiforme.
Fixed drug eruption
Well-circumscribed proliferation of an admixture of basaloid cells and cells with abundant vacuolated cytoplasm characteristic of sebaceous di�erentiation is seen.
Sebaceous epithelioma (sebaceoma)
dermal nodule of small blue cells arranged in sheets and trabeculae.
Merkel cell carcinoma
super�cial spreading. broad proliferation of large atypical melanocytes arranged in poorly formed nests at the dermoepidermal junction and within the dermis
Malignant melanoma
Vacuole
Collections of atypical lymphoid cells are seen in the epidermis (epidermotropism, Pautrier microabscesses).
Mycosis fungoides
epidermal ulceration and a dense dermal in�ltrate of lymphoid cells
Primary cutaneous large cell lymphoma
Epidermis
Parakeratosis containing collections of neutrophils, vacuolar alteration of the basal cell layer, and patchy lichenoid and perivascular lymphocytic in�ammation are seen. Scattered necrotic keratinocytes and extravasated red cells are present.
Pityriasis lichenoides acuta
RBCs
Vacuolar alteration of the basal cell layer is seen, above which there are necrotic keratinocytes.
Erythema multiforme
Necrotic keratinocytes
Vacuolar alteration of the basal cell layer is seen with scattered necrotic keratinocytes within the epidermis. Lymphocytes are present at the basal cell layer and extending into the epidermis, where they may surround the necrotic keratinocytes (satellite necrosis)
acute GVHD
Parakeratosis containing collections of neutrophils, vacuolar alteration of the basal cell layer, and patchy lichenoid and perivascular lymphocytic in�ammation are seen. Scattered necrotic keratinocytes and extravasated red cells are present.
Pityriasis lichenoides acuta
Necrotic keratinocytes in the epidermis, vacuolar alteration of the basal cell layer, and patchy lichenoid in�ammatory cell in�ltrate that obscures the dermoepidermal junction are seen. Histologic changes are similar to those seen erythema multiforme.
Fixed drug eruption
See neoplasm section
See neoplasms section for cysts
mild super�cial perivascular mixed in�ammatory cell in�ltrate and interstitial edema.
Urticaria
dilated blood vessels in the super�cial dermis surrounded by a mild perivascular in�ltrate of cells. Without a high degree of suspicion and special stains, it might be di�cult to notice that the cells are predominantly mast cells.
Urticaria pigmentosa, macular type
Giemsa stain highlights the mast cells in the in�ltrate.
Urticaria pigmentosa, macular typeEdema
Marked epidermal spongiosis with formation of spongiotic vesicles and a super�cial perivascular mixed in�ammatory cell in�ltrate are seen.
Spongiotic dermatitis
abundant eosinophils within the spongiotic vesicle, which favors a diagnosis of contact dermatitis.
contact dermatitis.
A super�cial and deep perivascular lymphocytic in�ltrate is associated with marked papillary dermal edema.
Polymorphous light eruption
palisade of histiocytes surrounding zones of myxoid degeneration of collagenThe granulomas are typically located in the upper dermis.
Granuloma annulareMyxoid
Palisading granulomas surrounding zones of �brinoid degeneration of collagen are present within the subcutaneous tissue.
Rheumatoid noduleFibrinoid
lymphocytes and histiocytes. The cytoplasm of the histiocytes shows characteristic ground-glass appearance.
Reticulohistiocytic granuloma
Ground glass
dense dermal in�ltrate composed of histiocytes and lymphocytes. Many of the histiocytes have foamy cytoplasm, and some are multinucleated.
Necrobiotic xanthogranuloma
Histologic section shows a disrupted follicle and neutrophilic in�ltrate
Acne vulgaris
Periodic acid–Schi� stain shows fungal forms in the hair shaft of an in�amed follicle.
Majocchi granulomaHair follicle, shaft
Sebo
rrhe
ic K
erat
osis
Roundish stu�
Syri
ngom
aM
icro
cyst
ic a
dnex
al C
A
well-circumscribed dermal proliferation of basaloid cells embedded in a cellular stroma containing keratinous cysts
Trichoepithelioma
follicular di�erentiation in the form of bulbs and papillae.
Trichoepithelioma
nests, strands, and ducts composed of monomorphous epithelial cellsthe ductal structures are lined two layers of cells, and some have elongated contours (tadpole-like).
Syringoma
See cyst sectionfocal epidermal ulceration covered by neutrophilic scale crust and a lobular proliferation of vascular spaces associated with stromal edema and in�ammatory cell in�ltrate, including neutrophils.
Pyogenic granuloma
Hem
angi
oma
Histologic section shows perivascular in�ltrate of neutrophils, neutrophilic nuclear dust, and extravasated red blood cells. Deposits of �brin are present in and around the damaged blood vessels.
Leukocytoclastic vasculitis
Vascular
mild super�cial perivascular mixed in�ammatory cell in�ltrate and interstitial edema.
Urticaria
A large blood vessel located in the subcutaneous tissue shows in�ammatory cell in�ltrate in the wall and an organizing thrombus within the lumen.
Thrombophlebitis
Histologic section shows well-formed vascular spaces in the dermis �lled with red blood cells
Hemangioma
epidermal hyperplasia, hyperkeratosis, and markedly dilated vascular spaces extending into the epidermis
Angiokeratoma
dilated blood vessels surrounded by a monomorphous population of round to oval cells.
Glomangioma
focal epidermal ulceration covered by neutrophilic scale crust and a lobular proliferation of vascular spaces associated with stromal edema and in�ammatory cell in�ltrate, including neutrophils.
Pyogenic granuloma
irregularly shaped vascular spaces lined by highly atypical endothelial cells with marked nuclear pleomorphism.
Angiosarcoma
Kapo
si
patch stage. slitlike spaces between the collagen bundles and extravasated red blood cells
Kaposi sarcoma
plaque stage. spindle cell proliferation and irregular vascular spaces
Kaposi sarcoma
Slits
irregularly shaped vascular spaces lined by highly atypical endothelial cells with marked nuclear pleomorphism.
Angiosarcoma
marked thickening of the dermis with sclerotic bands of collagen extending into the subcutaneous fat
Morphea
sclerotic collagen extending into the subcutaneous fat associated with lymphocytic in�ammation.
Morphea
nodular proliferation of �broblasts associated with irregularly thickened bundles of collagen.
KeloidCollagen
Sola
r ela
stos
is
Sola
r len
tigo
Elastin
palisade of histiocytes surrounding zones of myxoid degeneration of collagenThe granulomas are typically located in the upper dermis.
Granuloma annulare
Palisading (dermis)
Palisading granulomas surrounding zones of �brinoid degeneration of collagen are present within the subcutaneous tissue.
Rheumatoid nodule
Palisading (subQ)small nests of basaloid cells showing peripheral palisading.
BCC, super�cial
lymphocytes and histiocytes. The cytoplasm of the histiocytes shows characteristic ground-glass appearance.
Reticulohistiocytic granuloma
palisade of histiocytes surrounding zones of myxoid degeneration of collagenThe granulomas are typically located in the upper dermis.
Granuloma annulare
dermal in�ltrate of predominantly histiocytes, including multinucleated histiocytes containing foamy cytoplasm and nuclei arranged at the periphery in a wreathlike pattern (Touton giant cells). Lymphocytes are present in the background
XanthogranulomaGranuloma, Giant cells
zones of granulomas alternating with those of �brosis and extending into deep dermis
Necrobiosis lipoidica
histiocytes, including multinucleated giant cells surrounding zones of collagen degeneration in the deep dermis.
Necrobiosis lipoidica
Histologic section shows noncaseating granulomas within the dermis. The granulomas are composed of histiocytes with only a sparse lymphocytic component (naked tubercles).
Sarcoidosis
may resemble those of sarcoidosis. However, some of the histiocytes contain foreign-body material.
Foreign-body granuloma
poorly formed granulomas within the dermis.Some of the histiocytes have foamy cytoplasm
Leprosy
epidermal hyperplasia associated with suppurative and granulomatous in�ammation.
Blastomycosis Blastomycosis
Gomori methenamine silver stain demonstrates yeast forms of blastomycosis, some of which show characteristic broad-based budding.
dense dermal in�ltrate composed of histiocytes and lymphocytes. Many of the histiocytes have foamy cytoplasm, and some are multinucleated.
Necrobiotic xanthogranuloma
Parakeratosis containing collections of neutrophils, vacuolar alteration of the basal cell layer, and patchy lichenoid and perivascular lymphocytic in�ammation are seen. Scattered necrotic keratinocytes and extravasated red cells are present.
Pityriasis lichenoides acuta
dense perivascular and interstitial in�ltrate consisting predominantly of lymphocytes. A signi�cant number of the lymphocytes are large and contain enlarged hyperchromatic and irregular nuclei.
Lymphomatoid papulosis
in�ltrate contains a large number of plasma cells.
Secondary syphilis
Histologic section shows parakeratosis with neutrophils, epidermal hyperplasiaand a dense bandlike in�ammatory cell in�ltrate that obscures the dermoepidermal junction
Secondary syphilis
Plasma cell
Melanoma
hyperkeratosis, hypergranulosis, irregular epidermal hyperplasia, and a bandlike, predominantly lymphocytic in�ltrate that obscures the dermoepidermal junction. Melanophages are present in the dermal in�ltrate.
Lichen planus
hyperkeratosis with follicular plugging, atrophy of the epidermis, marked vacuolar alteration of the basal cell layer, and a thickened and smudged basement membrane. Perifollicular lymphocytic in�ltrate is present.
Cutaneous lupus erythematosus
lymphocyte
A super�cial and deep perivascular lymphocytic in�ltrate is associated with marked papillary dermal edema.
Polymorphous light eruption
Necrotic keratinocytes in the epidermis, vacuolar alteration of the basal cell layer, and patchy lichenoid in�ammatory cell in�ltrate that obscures the dermoepidermal junction are seen. Histologic changes are similar to those seen erythema multiforme.
Fixed drug eruption
Psoriasiform epidermal hyperplasia and a bandlike in�ltrate of lymphoid cells within a thickened papillary dermis are seen
Mycosis fungoides
epidermal ulceration and a dense dermal in�ltrate of lymphoid cells
Primary cutaneous large cell lymphoma
highly atypical lymphoid cells with irregular vesicular nuclei and coarse chromatin. These cells are typically positive for CD30.
Primary cutaneous large cell lymphoma
focal parakeratosis with neutrophils and mild super�cial perivascular in�ammation
Dermatophytosis
Neutrophil
di�use dermal in�ltrate consisting predominantly of neutrophils and extravasated red blood cells. Intact blood vessels help in di�erentiating this from leukocytoclastic vasculitis.
Sweet syndromedense di�use dermal in�ltrate of predominantly neutrophils. Blood vessels show plump endothelial lining. The in�ltrate is generally denser than that seen in Sweet syndrome.
Pyoderma gangrenosum
epidermal hyperplasia associated with suppurative and granulomatous in�ammation.
Blastomycosis
Histologic section shows perivascular in�ltrate of neutrophils, neutrophilic nuclear dust, and extravasated red blood cells. Deposits of �brin are present in and around the damaged blood vessels.
Leukocytoclastic vasculitis
see also sub-corneal neutrophil
separation at the dermoepidermal junction associated with aggregates of neutrophils, especially at the tips of the dermal papillae (papillary microabscesses).
Dermatitis herpetiformis
Periodic acid–Schi� stain shows fungal forms in the hair shaft of an in�amed follicle.
Majocchi granuloma
dilated blood vessels in the super�cial dermis surrounded by a mild perivascular in�ltrate of cells. Without a high degree of suspicion and special stains, it might be di�cult to notice that the cells are predominantly mast cells.
Urticaria pigmentosa, macular type
Giemsa stain highlights the mast cells in the in�ltrate.
Urticaria pigmentosa, macular type
Mast cells
dense, di�use dermal in�ltrate of mast cells
Urticaria pigmentosa
Immunohistochemical stain for mast cell tryptase highlights the mast cells.
Urticaria pigmentosa
Marked epidermal spongiosis with formation of spongiotic vesicles and a super�cial perivascular mixed in�ammatory cell in�ltrate are seen.
Spongiotic dermatitis
Mixed
mild super�cial perivascular mixed in�ammatory cell in�ltrate and interstitial edema.
UrticariaPerivascular
Eosinophil
A super�cial and deep perivascular and interstitial in�ltrate is arranged in a wedge shape
Insect bite reaction
High-power view shows the presence of frequent eosinophils within the in�ltrate.
Insect bite reaction
parakeratotic burrow containing body parts of the mite of scabies. The dermal in�ammatory cell in�ltrate typically contains frequent eosinophils.
Scabies
Histiocyte
plasma cells and histiocytes. Within the cytoplasm of the histiocytes, there are organisms that are 2 to 4 µm in size. A Giemsa stain will highlight the organisms.
Leishmaniasis
Dermal in�ltrate of histiocytic cells with abundant cytoplasm and irregular lobulated nuclei; many of the cells extend into the overlying epidermis
Langerhans cell histiocytosis
Immunohistochemical stain for CD1a shows strong positivity of the histiocytic cells.
Langerhans cell histiocytosis
See granulomas
In�ltrate
Dermis
Section shows a predominantly lobular pattern of lymphocytic panniculitis with associated hyaline fat necrosis.
Lupus profundus
sclerotic collagen extending into the subcutaneous fat associated with lymphocytic in�ammation.
Morphea
predominantly septal involvement by a �brosing process
Erythema nodosum
broadening of the septa of the subcutaneous fat by �brosis and granulomatous in�ammation.
Erythema nodosum
Panniculitis
Subcutaneous fat necrosis
predominantly lobular pattern of in�ammationlobules containing areas of fat necrosis and a moderately dense mixed in�ammatory cell in�ltrate, including lymphocytes and histiocytes. Multinucleated histiocytes containing needle-shaped crystals in radial array are a characteristic �nding.
Subcutaneous fat necrosis
Des
mop
last
ic m
elan
oma
DFS
PSpindle, storiform
nodular stage. solid proliferation of spindle-shaped cells associated with extravasated red cells. Nuclear atypia and mitotic �gures are present.
Kaposi sarcoma
arrector pili muscle type. Fascicles of smooth muscle cells are seen within the upper part of the dermis
Leiomyoma
vascular type. A deep, dermal, well-circumscribed nodule composed of smooth muscle cells that surround and merge with the vessels walls.
Leiomyoma
spindle-shaped cells with enlarged and hyperchromatic nuclei.Mitotic �gures are present.
Leiomyosarcoma
slender spindle-shaped cells in�ltrating and replacing the subcutaneous fat.
DFSP
deeply in�ltrative proliferation of spindle-shaped cells
DFSP
dermal proliferation of spindle-shaped cells with wavy nuclei and a loose myxoid stromaMast cells are typically present in the background
Neuro�broma
Palisaded and encapsulated neuroma. well-circumscribed nodule of spindle-shaped cells with elongated nuclei and a palisaded arrangement.
Neuro�broma
palisade of histiocytes surrounding zones of myxoid degeneration of collagenThe granulomas are typically located in the upper dermis.
Granuloma annulare
Palisading (dermis)
Palisading granulomas surrounding zones of �brinoid degeneration of collagen are present within the subcutaneous tissue.
Rheumatoid nodule
Palisading (subQ)small nests of basaloid cells showing peripheral palisading.
BCC, super�cial
SubQ
well-circumscribed, lobulated, and partly cystic dermal nodule
Clear cell (nodular) hidradenoma
lobules of cells with clear cytoplasm and ductal lumens lined by cells with decapitation secretions and cystic spaces �lled with eosinophilic material.
Clear cell (nodular) hidradenoma
compact, wet keratin in lumen of this cyst lined by strati�ed squamous epithelium no granular layer distinguishes (vs epidermal)
Trichilemmal cyst
cyst �lled with laminated keratin lined by strati�ed squamous epithelium WITH granular layer
Epidermal inclusion cyst
This cyst, lined by only two layers of cells, inner luminal row, outer myoepithelial cellslumen contains apocrine secretions
Hidrocystoma
thin epithelial lining covered by undulating keratin layer.
Steatocystoma
Cysts
cystic epidermal invagination into which papillary structures project
Syringocystadenoma papilliferum
In contrast to syringocystadenoma, this is a predominantly dermal nodule with cystic appearance
Hidradenoma papilliferum.
complex papillary fronds lined by columnar cells with decapitation secretions.
Hidradenoma papilliferum.
papillae are lined by two rows of cells: the luminal row is composed of columnar cells with decapitation secretions. Plasma cells are present within the stroma
Syringocystadenoma papilliferum
cystic epidermal invagination into which papillary structures project
Syringocystadenoma papilliferum
papillae are lined by two rows of cells: the luminal row is composed of columnar cells with decapitation secretions. Plasma cells are present within the stroma
Syringocystadenoma papilliferum
Syri
ngom
anests, strands, and ducts composed of monomorphous epithelial cellsthe ductal structures are lined two layers of cells, and some have elongated contours (tadpole-like).
Syringoma
Syringo___
Trichilemmoma
sharply de�ned proliferation of cells with clear cytoplasm resembling the outer root sheath of hair follicle.
well-circumscribed dermal proliferation of basaloid cells embedded in a cellular stroma containing keratinous cysts
Trichoepithelioma
follicular di�erentiation in the form of bulbs and papillae.
Trichoepithelioma
Trich___
Kapo
si
patch stage. slitlike spaces between the collagen bundles and extravasated red blood cells
Kaposi sarcoma
plaque stage. spindle cell proliferation and irregular vascular spaces
Kaposi sarcoma
Cleft
DFS
P
nodular stage. solid proliferation of spindle-shaped cells associated with extravasated red cells. Nuclear atypia and mitotic �gures are present.
Kaposi sarcoma
arrector pili muscle type. Fascicles of smooth muscle cells are seen within the upper part of the dermis
Leiomyoma
vascular type. A deep, dermal, well-circumscribed nodule composed of smooth muscle cells that surround and merge with the vessels walls.
Leiomyoma
spindle-shaped cells with enlarged and hyperchromatic nuclei.Mitotic �gures are present.
Leiomyosarcoma
Spindle
slender spindle-shaped cells in�ltrating and replacing the subcutaneous fat.
DFSP
deeply in�ltrative proliferation of spindle-shaped cells
DFSP
dermal proliferation of spindle-shaped cells with wavy nuclei and a loose myxoid stromaMast cells are typically present in the background
Neuro�broma
Palisaded and encapsulated neuroma. well-circumscribed nodule of spindle-shaped cells with elongated nuclei and a palisaded arrangement.
Neuro�broma
sharply demarcated epidermal proliferation composed of keratinocytes with pale cytoplasm. Parakeratosis and neutrophils in the parakeratosis and among the clear cells are typical �ndings.
Clear cell acanthoma Trichilemmoma
sharply de�ned proliferation of cells with clear cytoplasm resembling the outer root sheath of hair follicle.
Clear cells
papillomatous epidermal hyperplasia associated with prominent sebaceous lobules and poorly formed follicular units.
Nevus sebaceus
Well-circumscribed proliferation of an admixture of basaloid cells and cells with abundant vacuolated cytoplasm characteristic of sebaceous di�erentiation is seen.
Sebaceous epithelioma (sebaceoma)
super�cial spreading. broad proliferation of large atypical melanocytes arranged in poorly formed nests at the dermoepidermal junction and within the dermis
Malignant melanoma
Cytokeratin stain shows perinuclear dotlike positivity of the neoplastic cells.
Merkel cell carcinoma
Collections of atypical lymphoid cells are seen in the epidermis (epidermotropism, Pautrier microabscesses).
Mycosis fungoides
epidermal ulceration and a dense dermal in�ltrate of lymphoid cells
Primary cutaneous large cell lymphoma
Bubbles
con�uent parakeratosis and increased thickness of epidermis. The epidermis contains atypical keratinocytes with pleomorphic nuclei, dyskeratotic cells, and frequent mitotic �gures above the basal cell layer. The changes are con�ned to the epidermis, and therefore this lesion is considered a form of squamous cell carcinoma in situ.
Bowen disease
exoendophytic neoplasm, central cup-shaped cratersurrounded by proliferation of large keratinocytes with abundant glassy cytoplasm and minimal cytologic atypia di�erentiates this form of squamous cell carcinoma from the conventional squamous cell carcinoma. Neutrophilic microabscesses may be seen at the base of the neoplasm.
Keratoacanthoma
SCCSCC
The epidermal proliferation shows tunnel-like invaginations �lled with parakeratosis.The neoplasm in�ltrates as bulbous expansions of the rete.
Verrucous carcinoma
SCC-likeBCC
Poro
ma
small nests of basaloid cells showing peripheral palisading.
BCC, super�cialnodular proliferation of basaloid cells with peripheral palisading.
BCC, nodular
irregular lobules of pleomorphic basaloid cells with scattered mature sebocytes.Mitotic �gures and individually necrotic cells are present.
Sebaceous carcinoma
BCC-like
dermal nodule of small blue cells arranged in sheets and trabeculae.
Merkel cell carcinoma
cells with scant cytoplasm and irregular nuclei. Nucleoli are inconspicuous. Mitotic �gures and individually necrotic cells are present.
Merkel cell carcinoma
Trabecula
In�ltratedilated blood vessels in the super�cial dermis surrounded by a mild perivascular in�ltrate of cells. Without a high degree of suspicion and special stains, it might be di�cult to notice that the cells are predominantly mast cells.
Urticaria pigmentosa, macular type
Giemsa stain highlights the mast cells in the in�ltrate.
Urticaria pigmentosa, macular type
dense, di�use dermal in�ltrate of mast cells
Urticaria pigmentosa
Immunohistochemical stain for mast cell tryptase highlights the mast cells.
Urticaria pigmentosa
Mast cells
Dermal in�ltrate of histiocytic cells with abundant cytoplasm and irregular lobulated nuclei; many of the cells extend into the overlying epidermis
Langerhans cell histiocytosis
Immunohistochemical stain for CD1a shows strong positivity of the histiocytic cells.
Langerhans cell histiocytosis
Histiocytes
�broblasts and multinucleated histiocytes with foamy cytoplasm and hemosiderin pigment.
Dermato�broma
Psoriasiform epidermal hyperplasia and a bandlike in�ltrate of lymphoid cells within a thickened papillary dermis are seen
Mycosis fungoides
Collections of atypical lymphoid cells are seen in the epidermis (epidermotropism, Pautrier microabscesses).
Mycosis fungoides
epidermal ulceration and a dense dermal in�ltrate of lymphoid cells
Primary cutaneous large cell lymphoma
highly atypical lymphoid cells with irregular vesicular nuclei and coarse chromatin. These cells are typically positive for CD30.
Primary cutaneous large cell lymphoma
Lymphocytes
well-circumscribed dermal proliferation of basaloid cells embedded in a cellular stroma containing keratinous cysts
Trichoepithelioma
follicular di�erentiation in the form of bulbs and papillae.
Trichoepithelioma
Eccr
ine
Spir
oade
nom
a
well-circumscribed dermal nodule with occasional ductal lumina
Spiradenoma
sheets of larger cells with pale cytoplasm and smaller cells with scant cytoplasm. Globules of hyaline basement membrane–like material are present within the aggregations.
Spiradenoma
well-circumscribed dermal nodule composed of epithelial islands that are separated by thick hyaline sheaths and �t together like pieces of a puzzle
Cylindroma
Blobs
Der
mat
o�br
oma
Neu
ro�b
rom
a
well-de�ned dermal nodule of �broblasts and histiocytes.
Dermato�broma
�broblasts and multinucleated histiocytes with foamy cytoplasm and hemosiderin pigment.
Dermato�broma
Collagen
sharply demarcated intraepidermal proliferation of monomorphous cuboidal cells with scattered ductal lumina. The stroma is richly vascular.
PoromaMarked epidermal spongiosis with formation of spongiotic vesicles and a super�cial perivascular mixed in�ammatory cell in�ltrate are seen.
Spongiotic dermatitis (looks cystic)
abundant eosinophils within the spongiotic vesicle, which favors a diagnosis of contact dermatitis.
contact dermatitis (looks cystic)
deeply in�ltrative neoplasm composed of ductal structures and keratin-�lled cysts
Microcystic adnexal carcinoma
monomorphous epithelial islands in�ltrating between the skeletal muscle �bers.
Microcystic adnexal carcinoma
Microcystic
follicular di�erentiation in the form of bulbs and papillae.
Trichoepithelioma
sheets of larger cells with pale cytoplasm and smaller cells with scant cytoplasm. Globules of hyaline basement membrane–like material are present within the aggregations.
SpiradenomaFollicular Sy
ring
oma
Mic
rocy
stic
adn
exal
CA
nests, strands, and ducts composed of monomorphous epithelial cellsthe ductal structures are lined two layers of cells, and some have elongated contours (tadpole-like).
Syringoma
deeply in�ltrative neoplasm composed of ductal structures and keratin-�lled cysts
Microcystic adnexal carcinoma
monomorphous epithelial islands in�ltrating between the skeletal muscle �bers.
Microcystic adnexal carcinoma
Round structure
Neoplasmsand Cysts
See nevus section for melanocytic ddxSee vascular section for vascular ddx
Com
poun
d ne
vus
broad proliferation of monomorphous melanocytes arranged as nests extending deep into the dermis, where they surround the adnexal structures.
Congenital melanocytic nevus
Section shows nests of monomorphous melanocytes at the dermoepidermal junctionand within the dermis, where they show maturation with progressive descent
Acquired (compound) melanocytic nevus
Clark dysplastic type. Section shows junctional nests of melanocytes with bridging between the adjacent rete and associated concentric and lamellar �broplasia. The melanocytes are slightly large and contain melanin-laden cytoplasm. The dermal nests are surrounded by in�ammatory cell in�ltrate and melanophages
Compound nevus
Nests
Spit
z ne
vus
Hyperkeratosis and parakeratosis, epidermal hyperplasia, and a proliferation of spindle and epithelioid melanocytes are seen at the dermoepidermal junction and within the dermis. Clefts around the nests and eosinophilic globules are characteristic �ndings
Spitz nevusCleft
Section shows nests of melanocytes at the dermoepidermal junction and within the dermis, where they are surrounded by a dense in�ltrate of lymphocytes
Halo nevusLymphocytes
Lent
igo
sim
plex
Linear
Blue
nev
us
deep dermal proliferation of spindle-shaped melanocytes containing abundant melanin.
Blue nevusDeep
Intr
ader
mal
nev
usIn
trad
erm
al n
evus
Dys
plas
tic
nevu
s
Mel
anom
a
super�cial spreading. broad proliferation of large atypical melanocytes arranged in poorly formed nests at the dermoepidermal junction and within the dermis
Malignant melanoma
super�cial spreading. pagetoid melanocytes in a pagetoid pattern involving all levels of epidermis
Malignant melanoma nodular. Low-power view shows nodular proliferation of atypical melanocytes arranged as con�uent nests and sheets
Malignant melanoma, nodular
nodular. markedly atypical melanocytes with pleomorphic nuclei and prominent nucleoli. Mitotic �gures are present.
Malignant melanoma
Melanoma
Melanocytic
MDHero
The Practice of Surgical Pathology by MolaviDi�erential Diagnosis in Surgical Pathology by GattusoReferences:
Dermatopathology Ddx by Morphology