Sarcomatoid squamous cell carcinoma of the vulva expressing smooth muscle actin and S100 protein

Introduction Vulvar sarcomatoid squamous cell carcinoma has been rarely reported. Methods Case report and immunohistochemistry. Results The author herein reports a peculiar vulvar tumor. An 87-year-old woman with hypertension presented with a vulvar tumor, and admitted to our hospital. Gross examination showed an elevated tumor measuring 3 x 4 x 5 cm in the vulva near the urethra. An excisional biopsy was taken, and it showed proliferation and invasion of malignant spindle cells (70% in area) and malignant polygonal cells (30% in area). There were gradual transitions between vulvar squamous epithelium and these malignant tumor cells. Immunohistochemically, the malignant sarcomatoid cells (spindle and polygonal cells) were positive for cytokeratins, epithelial membrane antigen, vimentin, alpha-smooth muscle actin, S100 protein, and p53 protein. They were negative for melanosome, CD34, CD68, myoglobin, and CD45. Ki-67 labeling was 63%. A pathological diagnosis of sarcomatoid squamous cell carcinoma expressing smooth muscle antigen and S100 protein was made. The patient developed lung metastasis 2 months later, and suddenly died of unknown cause. Conclusion A rare case of vulvar sarcomatoid squamous cell carcinoma expressing S100 protein and alpha-smooth muscle actin is reported.