Radiologymovies - NEURINOMA DEL PENE

Neurinoma (Schwannoma or neurilemmoma) is an encapsulated tumor that arise from the Schwann cells of the peripheral nerve, therefore these lesions may occur anywhere in the body1,1a. Despite the rich enervation of the genital region, neurinomas are very rare in the penis2. Most of these lesions are benign and single, but can be multiple and malignant3.

CASE PRESENTATION :

A 51-years-old man presented to his primary care physician complaining of painless dysuria and sexual dysfunction. These symptom had been present for over 6 months. On palpation, no plaques were detected on the penis. Ultrasonography using a 12-MHz linear transducer (Acuson Sequoia 512; Siemens Medical Solutions) revealed a 4 x 3 cm oval well-defined mass, heterogeneous mostly hypoechogenic on grey-scale, in the penile root. The lesion was hypervascular on Color and Power Doppler US.

Magnetic resonance imaging was performed on a 1.5-T unit (Genesis Signa; GE Medical Systems, Milwaukee, WI) using a phased-array coil with the following sequences: axial, sagittal, and coronal T2-weighted and T1-weighted imaging after gadolinium injection. Magnetic resonance imaging confirmed ultrasound findings, demonstrating a 4.0 x 2.0 cm elongated and fusiform mass compressing the corpora cavernosa and corpus spongiosum on the right side of the penile shaft.

The lesion was covered by the tunica albuginea. Typical features of schwannoma were exhibited by the lesion, which was hypointense on T1 and hyperintense on T2 with hypointense foci and strongly enhanced; the shape was also typical with well defined borders and presence of a capsule. A cluster of small, serpiginous vessel was located on the distal pole of the mass, a finding often present in benign neural tumors. Multidetector Computer Tomography (Lightspeed Pro 16; GE Medical Systems, Milwaukee, WI, USA) was performed too, that demonstrated an oval hypodense mass in the unenhanced images and hypervascular after contrast-enhanced.

Gross pathology of the resected lesion revealed a rubbery fusiform mass approximately 4.0 x 3.0 cm, well circumscribed, and on cut section white-yellow appearance without colony display foci of hemorrhage.

Histologically the lesion is a spindle and oval cells tumour, characterized by being hypercellular almost throughout and by showing a fascicular or whorled growth “pattern” with only very rare nuclear palisading. There are very few scattered mitosis and a slight nuclear pleomorphism. Other features are the presence of a thick incomplete fibrous capsule with lymphocytic follicular infiltrates, circumscribed areas of myxoid changes (so called: Antony B areas) and blood vessels with thick hyaline walls. The cells showed positive immunostaining for CD34 and S100 protein and desmin-negativity.

FINAL DIAGNOSIS :

NEURINOMA OF THE PENIS

DISCUSSION

Schwannomas are common benign neurogenic tumors that arise from neural crest-derived Schwann cells of the peripheral nerve sheaths1. They may occur anywhere in the body and they usually are located on the head, neck or flexor surface of the extremities, but penis is a very rare site2. The tumor is usually solitary and grows slowly. Malignant schwannoma may be often in association with neurofibromatosis type II2,4.A review of the literature showed that only 28 cases, to our knowledge, have been described in the English literature^5,6,7,8,9,10.

The most reported schwannoma were single lesions, benign and unifocal, whereas multiple tumors were present only in 30% of cases. Multifocality is not related to malignancy. Malignant schwannoma is often associated with neurofibromatosis type II; in the review published by Catedra Garcia et al11, all the malignant neurinomas were close associated to Von Recklinghausen’s disease. The lesion we observed has been originated on the right side of the base of the penis, enclosed in the tunica albuginea and supposedly derived from minor nerve fibers; on the contrary, most of the cases previously described it arises on the dorsal surface of the penis, where there are the dorsal penile nerves ^5,6,7,8,9,10.

Our case was unusual also because most of the penile schwannoma described in the literature are located more distally in the penis. The clinical symptoms depend on the location and volume of the lesion; lesions may induce various secondary symptoms, such us pain, dysuria, prolonged voiding time and urinary retentior. Histologically, benign schwannoma are alternative pattern of Antony A and B areas. Antoni A areas are composed of compact spindle cells with nuclei forming palisades; Antoni B areas are regions with a lax and edematous structure, fewer cells and a myxoid stroma ^4,10.

The two cell patterns can be found within one same lesion. Our lesion had only Antoni B areas. Special staining techniques should be applied to establish the pathological diagnosis. The tumor cells express S-100 protein, which is essential for establishing the diagnosis, and prove negative for neuron-specific enolase and neurofilament markers; S-100 protein may be expressed by tumors derived from Schwann cells 12.

Schwannoma lesions are differentiated from other spindle cell neoplasms such us fibrosarcoma, neurofibroma and leiomyoma with immunohistochemical studies and electron microscopy. The treatment of choise consists of complete surgical excision. A regular follow-up is recommended, though post-excisional recurrence is infrequent8. Our patient was doing well with no evidence of recurrence 6 months post-resection.

BIBLIOGRAFIA :

Cotran R.S., Kumar V., Robbins and Cotran, Pathologic Basis of Disease: Peripheral Nerve Sheath Tumors, 7th ed. (2005), WB Saunders, Philadelphia. pp. 1411—1413 1a-Enzienger FM, Weiss SW. Benign tumors of peripheral nerves. In: Soft Tissue Tumours. 4th ed. St. Louis: Mosby; 2001:1111-1207

Mayersak J.S., Viviano C.J., Babiarz J.W., Schwannoma of the penis, J Urol, Volume: 153, (1995), pp. 1931--1932

Woodruff J.M., Kourea H.P., Luis D.N., et al. Schwannoma, Kleihues P., Cavenee W.K., (Ed.) Pathology and Genetics of Tumours of the Nervous System: World Health Organization Classification of Tumours, (2000), IARC Press, Lyon. pp. 164—166

Berard F., Grezard P., Ruffion N., et al. Solitary schwannoma of the balanopreputial sulcus. Ann Dermatol Venereol. Volume: 125(10), (1998), pp. 729—731.

Simeão Versos R., Louro N., Borges R., et al. Multiple schwannoma of penis, Actas Urol Esp. 2006 Sep; 30(8):824-8.

Loeser A., Katzenberger T., Meuller JG., et al. Solitary schwannoma of glas penis, Urology 2007 Nov;70(5):1007e.5-6.

Marshall J., Lin E., Dogra V. and Davis R. Schwannoma of the penis: preservation of the neurovascular bundle, Urology 2007 Aug;70(2):373.e1-3.

Jiang R., Chen J.H., Chen M., et al. Male genital schwannoma, review of 5 cases, Asian J Androl, Volume: 5, (2003), pp. 251—254.

Algaba F., Chivite A., Rodriguez-Villalba R., et al. Schwannoma of the penis: a report of 2 cases, J Androl, Volume: 24, (2003), pp. 651—652

Sato D., Kase T., Tajima M., et al. Penile schwannoma, Int J Urol, Volume: 8, (2001), pp. 87—89

Catedra Garcia A., Sanz Jaca JP.,Garmendia Olaizola G., et al. Schwannoma of the penis. Arch Esp Urol. 2001;54(7):713-715

Kubota Y., Nkada T., Yaguchi H., et al. Schwannoma of the penis. Urol Int 1993;51(2):111-113