Schwannoma of the penis, presenting as a scrotal mass, rare entity with an uncommon presentation.

Schwannomas are benign nerve sheath tumors that are seen either sporadically or in patients of neurofibromatosis. This tumor is common in head, neck, and extremities. Penis is a rare site for this tumor. To the very best of our knowledge, <34 cases of penile schwannoma have been reported in literature till now, but none had presented as scrotal mass. Here, we report a case of penile schwannoma in a 16-year-old male boy who presented in our outpatient department with a slowly growing scrotal mass. Our patient did not have any other feature of neurofibromatosis. The patient after investigation underwent surgical excision and had no recurrence on follow-up of 5 years.

INTRODUCTION

Schwannomas are benign encapsulated tumors of the nerve sheath which are either seen sporadically or in patients of neurofibromatosis. These tumors are common from peripheral nerve sheaths in head, neck, and extremities in the third decade of life. Schwannomas have been found to grow very slowly. Even though the penis has a rich nerve supply, penile schwannomas are very rare. To the best of our knowledge, <34 cases[1] have been reported till now in English literature, and ours is the largest of all the reported cases along with atypical presentation of scrotal mass.

CASE REPORT

A 16-year-old male presented to us with a painless slowly growing swelling in the scrotal region for the past 2 years [Figure 1]. There was no history of penile or scrotal trauma or any sexually transmitted disease. On examination, a firm nodular mass was found present in the left hemiscrotum pressing on the ipsilateral testis but free from the testis and attached to the penis [Figure 2]. The size of the swelling was 6 cm × 7 cm, and there was no inguinal lymphadenopathy. All blood investigations were within normal limits, and ultrasonography revealed a 7 cm × 8 cm hypoechoic mass present in the left scrotum pressing on the ipsilateral testis arising from the penis. Fine needle aspiration cytology revealed a benign tumor. Surgical exploration was done, and firm mass about 8 cm × 8 cm arising from the proximal corpora was found. The mass was excised [Figures 3 and 4], and tissue was sent for histopathological examination. Postoperative period was uneventful, and biopsy report revealed schwannoma Antoni A and Antoni B regions [Figure 5]. Immunohistochemistry revealed positivity for S-100. Follow-up till now, i.e., after 5 years is uneventful with the patient having normal erectile function.

Figure 1

Scrotal swelling

Figure 2

Mass on examination

Figure 3

Intraoperative photograph of mass excision

Figure 4

Excised mass

Figure 5

Histopathological slide showing Antoni A and Antoni B areas of schwannoma

DISCUSSION

Schwannomas are benign nerve sheath tumors which are very slow growing. Because they grow slowly, they are present for many years before diagnosis. Very rarely are these tumors malignant, and when found, they are associated with Recklinghausen's disease.[234] If the schwannoma is at distal penis, it may interfere with sexual intercourse. There is no definitive evidence about the relationship between schwannoma and erectile dysfunction,[567] but one case report raised doubt about association between erectile function and penile schwannoma.[8] Differential diagnosis of this superficial tumor in the penis should include lipoma, atheroma, sarcoma, Peyronie's disease, and fibrosis.[9] If the lesion presents as a scrotal mass, as was in our case, then testicular malignancy can also be considered as one of the differential diagnoses, but proper examination and imaging can easily differentiate between the two. Lipoma and atheroma being softer and more superficial can be easily differentiated from penile schwannoma. Peyronie's disease patients present with complaints of erectile dysfunction and painful intercourse which is extremely rare in cases of penile schwannoma. In addition to excision biopsy of the tumor, imaging studies, such as ultrasonography and magnetic resonance imaging, can be informative diagnostic modalities in diagnosing this rare tumor. The magnetic resonance signal is intermediate on T1-weighted images and bright on fat saturated T2-weighted images. The lesions also show homogeneous enhancement after injection of a gadolinium contrast. The signal changes are compatible with the myxoid content of the solid tumor, and these features help in diagnosing penile schwannoma preoperatively.[10] Fine needle aspiration cytology has been shown to help in preoperative diagnosis of this extremely rare tumor.[11] Histopathologically, the hallmark of a benign schwannoma are the biphasic Antoni A and Antoni B areas. Antoni A areas have compact spindle cells with indistinct cytoplasmic borders arranged in bundles or interlacing fascicles. Antoni B areas are characterized by spindle cells arranged haphazardly in the myxoid stroma. Immunohistochemically, schwannomas are stongly positive for S-100 protein.[12] None of the cases reported have had recurrence till follow-up.

CONCLUSION

Schwannomas of the penis are extremely rare but should be included in the differential diagnosis for solid penile tumors and scrotal masses as in our case. Most penile schwannomas are benign, and surgical excision is enough for management. Histopathology and immunohistochemistry help in diagnosing this extremely rare tumor.

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Conflicts of interest

There are no conflicts of interest.