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　Case Report Kitasato Med J 2014; 44: 104-106　

Neurofibroma of the penis due to neurofibromatosis type 1:von Recklinghausen's disease

Takahiro Hirayama,1 Kazumasa Matsumoto,1 Sho Minami,2 Shoji Nagi,1 Masatsugu Iwamura1

1 Department of Urology, Kitasato University School of Medicine2 Department of Applied Tumor Pathology, Kitasato University Graduate School of Medical Sciences

We report a case of neurofibromatosis type 1 (NF1), also known as von Recklinghausen's disease, witha primary neurofibroma of the penis that was treated surgically. A 38-year-old man presented withsevere pain from a penile mass localized in the left aspect of the proximal portion of the penile shaft.The mass was excised, and there was no adhesion between the mass and the tunica albuginea of the leftcorpus. Pathological examination revealed a neurofibroma. After surgery, the patient had no pain andmaintained penile sensation and erection. At the 12-month follow-up, there was no sign of recurrence.To our knowledge, only 14 cases of primary or solitary penile NF1 have been reported in the literature.

Key words: neurofibroma, von Recklinghausen's disease, penile mass

Introduction

eurofibromatosis type 1 (NF1), also known as vonRecklinghausen's disease, is a common autosomal

dominant disease caused by mutations in the NF1 genelocalized on 17q11.2 that encodes neurofibromin, withan incidence of 1 in approximately 3000 births. It ischaracterized by multiple pigmented cutaneous lesions(café-au-lait spots) and tumors of the skin and nerves.Because of the variable gene expression, only 50% of thepatients have a familial history. Neurofibromas aretumors that potentially arise anywhere in the body fromcranial, peripheral, or visceral nerves. However, primaryneurofibromas of the penis are extremely rare, especiallyin adults.1,2 We report an adult case with a primaryneurofibroma of the penis that was surgically treated.

Case report

A 38-year-old man with NF1 presented for evaluation ofa penile mass localized on the left aspect of the proximalportion of the penile shaft. NF1 had been diagnosed inthe patient during childhood. A diagnosis of NF1 isbased on clinical features and requires the presence of atleast two of the following major factors: six or more caféau lait spots, auxiliary or inguinal freckling, two or morecutaneous neurofibromas, one plexiform neurofibroma,characteristic bony defects, optic glioma, two or more

iris (Lisch) nodules, and a first-degree relative with NF1.3

The patient presented with two of the diagnostic criteria:specifically, more than six café au lait spots and inguinalfreckling. Results from visual and hearing examinationsat a previous hospital were normal. No familial historyof NF1 was elicited from the patient; however, genetictesting for NF1 or brain magnetic resonance imaging(MRI) were not performed owing to the patient's family'sdisagreement. He had suffered for several months withsevere pain and an uncomfortable sensation while walkingdue to the palpable penile mass, which was firm andelastic. MRI of the pelvis revealed a high-intensity masson the corpus (Figure 1). We diagnosed this mass as aneurofibroma, and it was surgically resected. There wasno adhesion between the mass and the tunica albugineaof the corpus, and the mass could be completely removed.After the surgery, the patient had no pain and maintainedpenile sensation and erection. Pathological examinationrevealed a neurofibroma, which was positive for S100(Figure 2). At the 12-month follow-up, there was nosign of recurrence.

Discussion

NF1 involves rare hamartomatous growth of neural crestcells that affects the supporting mesenchymal elementsand was first described by Friedrich Daniel vonRecklinghausen in 1882. NF1 affecting the genitourinary

N

Received 3 September 2013, accepted 19 September 2013Correspondence to: Takahiro Hirayama, Department of Urology, Kitasato University School of Medicine1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa 252-0374, JapanE-mail: thirayam@med.kitasato-u.ac.jp

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Figure 1. MRI showed a penile mass in the left proximal portion of the shaft (arrows).

Figure 2. Pathological examination revealed a neurofibroma with hematoxylin and eosin staining (left) andS100 immunostaining (right). The cells were strongly positive for S100. The presence of S100 immunostainingwas presumed to indicate that the stained cells were part of the neural crest Schwann cell lineage.

Table Patients with primary penile neurofibroma

Case Age History Treatment Author Year

1 29 y Neurofibibroma Not Mentioned Pelot et al. 1965 2 20 y Neurofibibroma Not Mentioned Romaszewski et al. 1969 3 25 y Neurofibibroma Surgery Dehner et al. 1970 4 23 y Neurofibibroma Surgery Dehner et al. 1970 5 19 y Neurofibibroma Surgery Dehner et al. 1970 6 at birth Neurofibibroma Surgery Dehner et al. 1970 7 at birth Neurofibibroma Surgery Fethiere et al. 1974 8 7 y Neurofibibroma Surgery Elliott et al. 1981 9 8 y Neurofibibroma Surgery Dwosh et al. 198410 27 m Neurofibibroma Surgery Kousseff et al. 199911 9 y Neurofibibroma Surgery Littejohn et al. 200012 8 y Neurofibibroma Surgery Pascual-Castroviejo et al. 200813 26 y Neurofibibroma Surgery Barros et al. 200814 31 y Neurofibibroma Surgery Caraffa et al. 200815 38 y Neurofibibroma Surgery Hirayama et al. (Present case) 2013

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tract is uncommon. Of the genitourinary tract tissues,the bladder is the most frequent site for neurofibromas,which occur in the penis extremely rarely.4 We found 14cases of primary or solitary penile NF1 in the literature(Table).1,4,5,8-10 Pascual-Castroviejo et al. reported thatonly 4 of 620 cases presented with primary genitalianeurofibromas (0.65%).5

Neurofibromas occasionally undergo malignanttransformation such as in cases of malignant peripheralnerve sheath tumors.6,7 MRI is the gold standard forpreoperative evaluation of tumoral extension from thegenitourinary tract to the pelvic and the lumbosacralregions, and axial images are more valuable than anyother view.5 Data of this nature are sparse in the urologicliterature, however, because neurofibromas of the urinarytract are so rare. It is estimated that malignancy occurs in5% to 30% of the cases.6

Garaffa et al. reported a young male patient with apenile neurofibroma which was associated with erectiledysfunction.10 The dorsal neurovascular bundle (DNB)was mobilized off the mass that was adherent to the tunicaalbuginea of the corpus. At the 6-month follow-up afterthe surgery, erectile dysfunction persisted. Barros et al.reported another young male who had difficulty withsexual intercourse owing to a penile neurofibroma.8 Acomplete resection of the mass was also performed inthat case. The mass was adherent to the tunica albugineaof the corpus but not contiguous with the DNB. Thepatient subsequently recovered with maintenance ofpenile function and no pain. In the present case, themass, which did not involve the tunica albuginea of thecorpus or the DNB, could be completely resected and thepatient recovered well.

Neurofibroma should be considered in the differentialdiagnosis of perineal pain, especially when palpablenodules are present. The treatment goal of neurofibromais complete resection, avoiding progression, andmalignant degeneration. Therefore, a complete excision

of penile neurofibromas preventing DNB at an optimaltime is paramount not only to histologically confirm thenature of the mass but also to maintain function andcosmetic appearance.9

References

1. Littlejohn JO, Belman AB, Selby D. Plexiformneurofibroma of the penis in a child. Urology 2000;56: 669.

2. Wallace MR, Marchuk DA, Andersen LB, et al. Type1 neurofibromatosis gene: identification of a largetranscript disrupted in three NF1 patients. Science1990; 249: 181-6.

3. National Institutes of Health Consensus DevelopmentConference. Neurofibromatosis: Conferencestatement. Arch Neurol 1988; 45: 575-8.

4. Kousseff BG, Hoover DL. Penile neurofibromas.Am J Med Genet 1999; 87: 1-5.

5. Pascual-Castroviejo I, Lopez-Pereira P, Savasta S,et al. Neurofibromatosis type 1 with external genitaliainvolvement presentation of 4 patients. J PediatrSurg 2008; 43: 1998-2003.

6. Rodó J, Medina M, Carrasco R, et al. Enlarged penisdue to a plexiform neurofibroma. J Urol 1999; 162:1753-4.

7. Parekh N, Cockrell E, McMahon D. Malignantperipheral nerve sheath tumor of the penis: a casereport and review of the literature. Urology 2013;81: 1067-8.

8. Barros R, Cavalcanti AG, Favorito LA. Plexiformeneurofibroma with compromising of the penilefunction. Urology 2008; 71: 546.e9-10.

9. Dehner LP, Smith BH. Soft tissue tumors of thepenis. A clinicopathologic study of 46 cases. Cancer1970; 25: 1431-47.

10. Garaffa G, Bettocchi C, Christopher N, et al.Plexiform neurofibroma of the penis associated witherectile dysfunction due to arterial steeling. J SexMed 2008; 5: 234-6.

A primary penile neurofibroma