Giant Primary Cutaneous Myoepithelial Carcinoma of the Left Thigh With Inguinal and Pelvic Lymph Node Metastases.

Myoepithelial carcinoma is an exceedingly rare malignancy, particularly when originating from the skin. It frequently arises from malignant transformations of pleomorphic adenomas in various locations such as the parotid gland, breast, soft tissues, and lungs. Primary cutaneous myoepithelial carcinoma is exceptionally rare, often leading to delayed diagnosis. We report a case of giant primary cutaneous myoepithelial carcinoma of the left thigh, initially misdiagnosed as squamous cell carcinoma (SCC). The patient, a 64-year-old male, presented with a rapidly enlarging, ulcerated, and necrotic skin lesion. The initial presentation mimicked SCC. Due to the large tumor size and anemia caused by the tumor, the patient underwent a reduced-dose chemotherapy regimen (cytarabine plus aclarubicin chemotherapy) to shrink the tumor, enabling successful local surgical resection. Post-surgery, the patient received radiotherapy and tegafur gimeracil oteracil potassium, resulting in disease control without progression for two years. This case highlights the diagnostic challenges of myoepithelial carcinoma, which can mimic SCC among numerous other tumors. Accurate diagnosis relies on immunohistochemical staining and careful pathological evaluation. The case underscores the importance of considering myoepithelial carcinoma in the differential diagnosis of ulcerative tumors.