Squamous cell carcinoma arising in mature cystic teratoma with sigmoid invasion.

Malignant transformation in a mature cystic teratoma (MCT) is rare occurring in 1.8% out of 8000 cases of MCT. The most common histological types are squamous cell carcinoma (SCC) followed by adenocarcinoma and melanoma. Clinically, these tumors are usually asymptomatic but may be discovered accidentally during gynecologic examination due to mass effect. We present cytology and histology correlation of a rare case of SCC arising in a dermoid cyst with metastasis to sigmoid.