Myopericytoma: A Rare Perivascular Neoplasm – Case Report

Abstract

Devi Shanker Malik, Mahipal Singh, B S Dhakad and Srujana Kushtagi

Introduction: Myopericytoma is a rare, typically benign perivascular tumour originating from myopericytes. While it shares morphologic features with other myoid neoplasms, its distinct concentric growth pattern and specific immunohistochemical profile are diagnostic hallmarks. We present a case of myopericytoma to highlight its clinical presentation and the diagnostic rigor required to differentiate it from its mimics.

Case Presentation: A 69-year-old male presented with a slow-growing, painless subcutaneous mass in the distal part of left leg for last 5-6 months. Clinical findings were non-specific, so, initially diagnosed as a soft tissue tumour. His ultrasound demonstrated a well-defined heterogeneously hyperechoic lesion with mild internal vascularity seen in subcutaneous planes, superficial to Tendo-Achilles (closely abutting it) at posterior aspect of distal leg. A benign lesion?

Surgical excision of this soft tissue tumour was done under regional anaesthesia.

Histopathology reveals a circumscribed lesion composed of interlacing bundles of smooth muscle cells with elongated, blunt ended nuclei and eosinophilic cytoplasm. Numerous thick-walled vascular channels are interspersed within the smooth muscle bundles. Endothelial lining of vessels is intact. Suggestive of Spindel cell neoplasm.? Vascular Leiomyoma (Angioleiomyoma). Immunohistochemical analysis showed diffuse positivity for Smooth Muscle Actin (SMA) and h-Caldesmon, while Desmin, CD34, and S100 were negative, confirming the diagnosis of myopericytoma.

Discussion: Myopericytoma exists on a morphological continuum with myofibroma and angioleiomyoma. The absence of desmin staining in this case was pivotal in excluding angioleiomyoma, while the lack of a biphasic growth pattern ruled out myofibroma. Although usually benign, recognizing the myopericytic phenotype is essential for excluding malignant variants and ensuring appropriate surgical management.

Conclusion: This case underscores the importance of considering myopericytoma in the differential diagnosis of subcutaneous spindle cell tumours. A combination of characteristic "onion skin" morphology and a targeted IHC panel is essential for an accurate diagnosis and a favourable clinical outcome.