Verocay body prominent schwannoma of penis: an unusual localization for this lesion

To the Editor, Schwannoma is a common neoplasm of peripheral nerves. Rarely intracranial parenchymal and intramedullary schwannomas have been reported. In spite of the rich sensitive innervation of the penis, penile schwannomas are extremely rare. To the best of our knowledge, only 26 cases have been reported in the literature. We describe the case of a 78-yearold white man without clinical history or stigmata of neurofibromatosis who presented to the dermatology clinic complaining of a subcutaneous indurated painless nodular mass proximal to the right side of the glans, measuring 0.5 cm in diameter. The neoplasm was present for several months and was slowly enlarging without adhesion to the skin, only showing mild erythema around the glans. No palpable inguinal lymph nodes were noted. Excisional biopsy was performed. The tumor was well encapsulated without involvement of the Buck’s fascia or any other neighbor structure. Histologically, it was composed of spindle-shaped Schwann cells with alternating areas of tightly compacted cells with fusiform and tapered nuclei (Antoni A) and less cellular, loosely textured meshwork of cells with rounded, hyperchromatic nuclei and short disordered processes (Antoni B). In the Antoni A areas, there was palisades created by alignment of nuclei alternating with cytoplasm-rich, hypereosinophilic, anucleated zones (Verocay bodies), which constituted approximately 80% of the tumor bulk. Zelger et al. have described this finding as a distinct variant of cutaneous schwannoma known as Verocay body prominent schwannoma’ commonly found in the head and neck region, which to our knowledge has not been reported in the penis (Figs. 1 and 2). Fibrosclerosis of vessels was also observed. Neither mitosis nor nuclear atypia was seen. These findings led to the diagnosis of schwannoma that was confirmed by immunohistochemistry showing intense and diffuse positivity of the neoplastic cells for the S-100 protein (Fig. 3). The neurofilament protein stain did not show any intratumoral axons; however, it was focally positive in the subcapsular region, which corresponded to the remnants of the parent nerve. Following surgery, the patient had an uneventful recovery. Schwannomas comprise approximately 8% of intracranial and 29% of primary spinal canal tumors. The occurrence age ranges from 2 to 78 years with the mean being 35.9 years. They can be solitary or as part of a systemic disease (association with Von Recklinghausen disease). Recently, it has been recognized that some patients with multiple schwannomas lack vestibular tumors, this group constitute a third form of neurofibromatosis known as schwannomatosis. Schwannomas are usually encapsulated benign tumors composed of neoplastic Schwann cells, and although sensory nerves are the preferred sites of origin, motor and autonomic nerves may also be affected. Most of the penile schwannomas are solitary and benign, but multiple lesions have also been reported. On the reported cases, the most common location was in the penile shaft followed by the prepuce and glans. Only four malignant penile schwannomas have been described in the literature (three of them were associated with Von Recklinghausen disease), and none of the benign tumors were associated with this disease. These tumors are usually asymptomatic until they are large enough to induce secondary symptoms, such as pain, dysuria, urinary retention and erectile dysfunction. An accurate preoperative clinical diagnosis of schwannoma in this location is difficult, but ultrasonography, CT or MRI can be helpful. The clinical differential diagnosis includes fibroma, lipoma, Peyronie’s disease, fibrosis because of autoinjection for impotence and angiomatous tumors (i.e. capillary or cavernous hemangiomas). Most of the