Cytomorphologic Features of Hepatic PEComa Diagnosed by Fine-Needle Aspiration Biopsy.

Perivascular epithelioid cell tumours (PEComas) are rare mesenchymal neoplasms with characteristic myomelanocytic differentiation and limited descriptions in fine-needle aspiration (FNA) specimens. A woman in her 30s with a history of ALK-positive anaplastic large cell lymphoma in remission was found to have a 2.1-cm hepatic mass during evaluation of persistent liver function abnormalities. Ultrasound-guided FNA demonstrated a cellular neoplasm composed of loosely cohesive clusters and singly dispersed epithelioid to spindle cells with abundant eosinophilic cytoplasm, mild to moderate nuclear atypia and prominent nucleoli. Immunohistochemical studies showed positivity for smooth muscle actin, caldesmon, HMB-45 and Melan-A, supporting a myomelanocytic phenotype. Molecular testing identified pathogenic TSC2 splice-site mutations. Subsequent resection confirmed hepatic PEComa, epithelioid angiomyolipoma variant. This case highlights the characteristic cytomorphologic, immunophenotypic and molecular features of hepatic PEComa and demonstrates the value of FNA with ancillary testing in establishing a preoperative diagnosis and excluding morphologic mimics.