Squamous cell carcinoma in mature cystic teratoma of the ovary.

INTRODUCTION Malignant transformation is a rare complication of mature cystic teratoma, with squamous cell carcinoma as the most common malignancy (in 75% of cases). In this article we present a case of a well-differentiated squamous cell carcinoma arising in a mature cystic teratoma and discuss the morphological and clinico-pathological features of malignant transformation in teratoma. CASE REPORT An 80-year-old woman with symptoms of acute abdomen underwent left salpingo-oophorectomy. Gross examination showed a cystic mass measuring 20 cm in diameter, with papillary formation on its internal surface. Histology revealed a well-differentiated squamous cell carcinoma arising in mature cystic teratoma. Squamous epithelium surrounding the tumor was dysplastic. CONCLUSION Squamous cell carcinoma in mature cystic teratoma is a rare pathologic event and in most cases it is an accidental pathohistological finding.