Male genital schwannoma, review of 5 cases

Rui Jiang¹, Jiang-Hua Chen¹, Ming Chen², Qi-Meng Li¹

Asian J Androl 2003 Sep; 5: 251-254           

Keywords: neurilemmoma; genital neoplasms

Abstract

Aim: To study the clinical features of male genital schwannoma. Methods: Five male patients with genital schwannoma admitted from 1991 to 2000 were reviewed. The lesions were located in the prostate, spermatic cord, testis or penis. Tumors were simply resected in 3 patients and radically eradicated in 2. Results: The average age of the cohort was 37 years. The most common sign at presentation was a palpable genital mass accidentally discovered by the patient or detected by the physician during a physical check. Diagnosis was made through postoperative pathological examination. Follow-up ranged from 2 years to 6 years (mean 4.5). Four cases were cured by simple excision and 1 patient with malignant testis schwannoma died of recurrence 1 year after surgery. Conclusion: Owing to the lack of characteristic clinical manifestation, the final diagnosis relys on postoperative pathological examination. S-100 and vimentin are useful markers for the diagnosis of these tumors.

1 Introduction

Schwannomas are rare tumors of the male genital system. There have been only scattered reports of the tumor involving the penis [1], tunica vaginalis testis [2], seminal vesicle [3] and prostate [4]. Because of their rarity and non-specific presentations, misdiagnoses are common. In this article we reported 5 cases of schwan-nomas originated from the male genital system, including the prostate, spermatic cord, testis and penis and their clinical manifestation, diagnosis and management were discussed.

2 Patients and management

Between January 1991 and December 2000 there were 1574 patients with male genital tumor treated at our hospitals. Of them 5 (0.32 %), aged 20 years ~ 65 years (mean: 37), were identified as genital schwannoma. The interval between onset of symptoms and diagnosis ranged from 5 days to 7 years. All 5 cases had no other sites of involvement at the time of presentation. Radiographic evaluation included the use of ultrasonography and computed tomography (CT). The diagnosis was confirmed postoperatively by pathological examination. All cases were examined immunohistochemically by the strep-tavidin peroxidase conjugated technique. The S-100, vimentin and smooth-muscle actin (SMA) antibodies were used. Tumors were simply resected in 3 patients and radically eradicated in the other 2.

Case 1: A 38-year-old man presented with a gradually enlarging left scrotum for 2 years. On palpation, the left testis was swollen with a firm consistency, but was smooth, painless and movable. The demarcation between the epididymis and testis was clear. Transillumination result of the left scrotum was negative. The spermatophore and the prostate were normal. The serum tumor markers, including alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG), were normal. Scrotal ultrasound examination revealed a well-circumscribed and hypoechoic mass measuring 5 cm 5 cm 4 cm. Exploration of the left scrotum was carried out. The lesion was rounded and smooth. Frozen section revealed that the lesion was mesenchymal tumor with bundles of spindle cells. Radical orchiectomy was performed. On cut sections the lesion was gray and whorled. Histolo-gically, the tumor was encapsulated and composed of bundles of spindle cells with hyperchromasia and big nuclear and the mitotic rate was over 20 mitoses per 10 high-power fields, which was consistent with malignant schwannoma (Figure 1A). The tumor cells were weakly positive to S-100 protein. The pathologic diagnosis was malignant testicular schwannoma. The patient died of metastatic disease 1 year after operation.

Case 2: A 65-year-old man presented with intermittent, painful and gross hematuria for 5 days. Digital rectal examination revealed IIIº enlarged prostate without nodules and tenderness. Serum prostate specific antigen was 1.8 ng/mL (normal value: <4.0). Uroflowmetry indicated lower urinary tract obstruction. On cystoscopy the catheter was impeded at the level of the anterior bulbous urethra and failed to pass into the posterior urethra. Ultrasonography revealed left hydronephrosis and prostatic hypertrophy. CT showed a smoothly outlined mass in the prostate region with an attenuation of 40 Hounsfield units. The preoperative diagnosis was benign prostatic hypertrophy complicated with left hydronephrosis. Transvesical suprapubic prostatectomy was performed and an enlarged prostate was found measuring 6 cm 6 cm with clearly dilated submucosal vessels projecting into the bladder adjacent to the left ureteral orifice. The left lobe of the prostate was significantly larger than the right. The demarcation between the lesion and the tough surgical capsule is easily identified. The mass, measured 6 cm 6 cm 7 cm and weighed 500 g, was bluntly enucleated without difficulty. The cutting surface of the mass was gray and fleshy. Microscopically, the lesion consisted of spindle cells arranged mainly in Antoni A pattern (Figure 1B). Immunohistochemically, the tumor cells were positive to S-100 (Figure 1C) and vimentin (Figure 1D). The histological and immunohistochemical findings were consistent with those of schwannoma of the prostate. He was alive with no evidence of recurrence during 2-year follow-up.

Case 3: A 20-year-old man with a history of left scrotal swelling for 2 years and local pain for 20 days. Physical examination revealed a mass with dilated veins at the left scrotal skin. A hard and well-circumscribed mass measuring 8 cm 5 cm 6 cm closely adherent to the cord was palpable near the external inguinal ring. The mass was tender and partly adherent to the scrotal wall. The left testis was atrophic, measuring 1 cm 1.5 cm 1.5 cm. The contralateral scrotal content was normal. The transillumination result was negative. Blood studies revealed an increased erythrocyte sedimentation rate (90 mm/h) and a white blood count of 10.2 10⁹/L. Tumor markers, including AFP and carcinoembryonic antigen (CEA), were negative. A scrotal and groin ultrasound scan revealed a hypoechoic solid mass potentially involving the left spermatic cord and testis. On surgical exploration, a mass 4 cm 3 cm 3 cm was seen apparently arising from the thickened spermatic cord. The lesion, firm and adherent to the scrotum skin, was mainly located at the external inguinal ring. The mass, adhering to a certain extent to the testis and skin, compressed the testis, while its free portion was smooth. The mass, the left testis and 2-cm surrounding scrotal skin were resected. The cut surface revealed a solid yellowish-gray tumor with organized blood clot. Histologically, the lesion was composed of spindle-shaped cells with elongated polymorphic nuclei. The outline was irregular and vague. Immunohistochemically, the tumor cells were positive to S-100 and negative to SMA. The pathologic diagnosis was left spermatic cord anaplasic schwannoma with hemorrhage and necrosis and left testicular compression atrophy and necrosis. He was alive with no evidence of recurrence during 6-year follow-up.

Case 4: A 28-year-old man presented with a 7-year history of a slowly enlarging painless nodule on the coronal sulcus of the penis, measuring 1 cm 1 cm 2 cm at admission. The nodule invaded the glans and the distal penile shaft without penile deviation and pain on erection. There were no enlarged inguinal nodes. Results of urinalysis were normal. The diagnosis of penis schwannoma was made by biopsy. Partial penectomy was performed and a 5 cm stump of penis was left. The nodule was firm and appeared to be grossly homogeneous. Immunohistochemically, the tumor cells were positive to S-100 and negative to SMA. The pathologic diagnosis was schwannoma of the penis. The sexual function was apparently normal with the penile stump. He was healthy with no evidence of recurrence during 6-year follow-up.

Case 5: A 34-year-old man presented with a painless mass on the right side of the penis for 2 years. Nothing particular was noted with the urological and medical history. Physical examination revealed a smooth and firm mass measuring 0.5 cm 0.5 cm and confined to the middle third of the penile shaft. No inguinal node was palpable. The mass was excised completely and was found to be encapsuled and consisted of spindle cells. Immunohistochemically, the tumor cells were positive to S-100 and vimentin. The pathologic diagnosis was schwannoma of the penis. Erectile function was maintained after surgery. He was alive with no evidence of recurrence during 4-year follow-up.

Figure 1. Male genital schwannoma: histology and immunohistochemical markers. A: Malignant testicular schwannoma showing fascicles of neoplastic spindle-shape cells with hyperchromasia, big nuclei, mitotic figures and little cytoplasm (HE staining, 200); B: Benign penile schwannoma. Antoni A areas showing compact spindle-shape cells and Verocay bodies (HE staining, 100); C: Immunohistochemical staining for S-100 showing strong reactivity of tumor cells (200); D: Immunohistochemical staining for vimentin showing reactivity of tumor cells (100).

3 Discussion

Schwannomas are rare tumors originated from the schwann cell of the peripheral nerve sheaths. They are generally encountered in young and middle-aged adults at the flexor surfaces of the extremities, neck and mediastinum [5] and are exceedingly rare in the male genital system. To our knowledge Case 3 of this series was the first case of primary solitary spermatic cord schwannoma so far reported in the literature. Schwannoma is originated from the Schwann cells ensheathing the small nerve twigs or from ectopic Schwann cells often locating at the muscularis propria. The tumor is mostly benign, solitary and usually grows slowly. Malignant schwanno-mas may either be solitary or in association with Von Recklinghausen's disease approximately with equal frequency [6]. The etiology of schwannoma was not well known, but seemed to be related with neurofibromatosis type II gene loss or alteration [7].

The clinical and radiographic findings of male genital schwannoma are non-specific and the lesion may be misdiagnosed as other solid tumors. These tumors are usually asymptomatic until they are large enough to compress the neighboring structure and induce various secondary symptoms, such as pain, dysuria, prolonged voiding time, urinary retention, etc. The most common sign at presentation was a solitary, painless and firm genital mass. Ultrasonography, CT or magnetic resonance imaging are helpful in locating the site and delineating the mass. Though we did not see accompanying Von Recklinghausen's disease, a careful search for Von Recklinghausen's disease should be a part of the evaluation as based on literature reports [6].

It is difficult to obtain an accurate clinical diagnose preoperatively. It has been suggested that pathological examination, including the immunohistochemical profile, would be more reliable in establishing a definitive diagnosis of male genital schwannomas. Upon surgical exploration, the tumor generally appears to be firm, circumscribed, encapsulated and not adhering or invading the surrounding tissues. Pressure necrosis of the adjacent tissue usually suggests that the tumor is malignant. The cutting surface of the mass was gray and fleshy. Histologically, benign schwannoma are composed of an alternating pattern of Antoni A (Figure 1B) and B areas, the major pattern being Antoni A in the present series. The neoplastic cells of malignant tumor usually exhibit hyperchromasia and variations in the nuclear size and shape with frequent mitotic figures. A tumor should be suspected malignant if it contains epithelial glandular structures, no matter how well differentiated they are [8]. Special staining techniques should be applied to establish the pathological diagnosis. Immunostain for S-100, vimentin and leucine-7 will be positive while epithelial membrane antigen and SMA, negative. Unlike benign schwannoma, the pattern of staining for S-100 protein in malignant forms is usually very faint and focal [9]. Schwannoma lesions may usually be differentiate from other spindle cell neoplasms such as fibrosarcoma, neurofibroma and leiomyosarcoma by immunohistochemical studies and electron microcopy [9].

The therapeutic principle for male genital involvement is similar to that in managing schwannoma elsewhere in the body. A conservative surgical approach with complete excision of the mass is the most advisable treatment [10]. In this series, the schwannomas mostly arised from the peripheral nerve sheath without adherence to the major nerve trunk, therefore, we advocated simple enucleation of the mass. However, with malignant tumor, extensive resection was indicated to improve the survival rate. Local resection, such as partial penec-tomy, is an effective surgical approach that would preserve erectile function. Regular follow-up is necessary, though post-excisional recurrence is infrequent.

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Correspondence to: Dr. Rui Jiang, Kidney Diseases Center, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou 310003, China.
Tel: +86-571-8723 0545
E-mail: jiangru8847@sina.com
Received 2002-12-12      Accepted 2003-06-16