以腹股溝－陰囊腫塊表現之陰莖周邊神經鞘瘤：病例報告

葉則言、黃志平、張議徽

中國醫藥大學附設醫院 泌尿部

Peri-penile Schwannoma Presenting as an Inguinoscrotal Mass:

A Case Report

Tse-Yen Yeh, Chi-Ping Huang, Yi-Huei Chang

Department of Urology, China Medical University Hospital, Taichung, Taiwan

Introduction: Peri-penile schwannoma is a rare benign peripheral nerve sheath tumor. Because clinical and radiologic findings are often nonspecific, establishing a definitive preoperative diagnosis can be challenging.

Case report: A 63-year-old man presented with recent-onset left inguinal discomfort. Physical examination revealed a mildly tender, approximately 2.5-cm left hemiscrotal mass. Scrotal ultrasonography demonstrated a 2.5 × 2.0 cm heterogeneous mass near the left spermatic cord. Penile MRI identified a well-defined 27-mm lesion in the left peri-penile region causing focal indentation of the penile shaft, with iso- to high signal intensity on T1-weighted imaging and heterogeneous signal intensity on T2-weighted and diffusion-weighted imaging. Dynamic contrast-enhanced MRI showed early and progressively homogeneous enhancement. The differential diagnosis included angiosarcoma and neurogenic tumor, while malignancy could not be excluded. Complete excision was performed under general anesthesia with a separately submitted margin specimen. Histopathology confirmed schwannoma composed of spindle-cell proliferation with alternating cellularity and degenerative change. Immunohistochemistry demonstrated diffuse S-100 positivity with retained nuclear H3K27me3 expression, while CD34 and synaptophysin were negative. The margin specimen was tumor-free.

Discussion: This case highlights the diagnostic dilemma of peri-penile masses: despite well-circumscribed morphology and homogeneous enhancement, imaging overlap with other soft-tissue neoplasms may preclude reliable exclusion of malignancy. Accordingly, complete excision provides both definitive diagnosis and treatment while supporting functional preservation in this anatomically sensitive region. Retained nuclear H3K27me3 expression serves as supportive evidence against H3K27me3 loss reported in many MPNSTs, strengthening the benign interpretation when correlated with morphology and S-100 positivity.

Conclusions: Peri-penile schwannoma is very rare with only few case report, but it remains an important consideration in the differential diagnosis of peri-penile/inguinoscrotal masses. Radiologic–pathologic correlation remains essential, and complete excision with margin assessment is a pragmatic approach for diagnosis and local control.