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

Abstract

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.

Keywords: case report; chemotherapy; myoepithelial carcinoma; skin cancer; surgical resection.

Figure 1. Clinical presentation of the tumor

(A) A clinical image of the 20×20 cm pedunculated, red, raised lesion on the posterior aspect of the left thigh. The lesion showed an ulcerated and eroded surface with black and yellow necrosis. (B) A clinical image of the marked lymphadenopathy in the left inguinal region.

Figure 2. CT imaging findings

(A) A contrast-enhanced CT image showing the large mass in the posterior left thigh, with areas of enhancement and necrosis. The tumor and necrotic areas are indicated. (B) A CT image showing multiple enlarged lymph nodes from the left external iliac to the para-aortic regions.

Figure 3. Clinical images

(A) Tumor resection revealed partial infiltration into the underlying muscle. (B) After the resection, a split-thickness skin graft was performed.

Figure 4. Histological and immunohistochemical findings

(A) Histological slide showing the tumor with multiple, nodular, basophilic tumor nests infiltrating the dermis without a capsule; Magnification: x10. (B) High magnification view of the tumor cells exhibiting marked nuclear atypia with prominent nucleoli and numerous mitotic figures; Magnification: x100. (C) Immunohistochemical staining for calponin. (D) Immunohistochemical staining for α-SMA. (E) Immunohistochemical staining for HHF-35. (F) Immunohistochemical staining for PLAG1.