Squamous cell carcinoma arising within a mature cystic teratoma with invasion into the adjacent small intestine: a case report.

Malignant transformation in a mature cystic teratoma (MCT) is rare, with a reported incidence of approximately 1% to 3%. To our knowledge, no case has been reported previously with the invasion of malignant tumor of MCT into the adjacent small intestine. We report a case of squamous cell carcinoma arising within a MCT and invading into the adjacent small bowel. The patient is a 73-yr-old African American woman who noted the presence of a relatively asymptomatic abdominal mass over the past 40 yr. The mass had become more symptomatic over the past several months, with right-sided abdominal pain and constipation. She underwent an exploratory laparatomy, which demonstrated a cystic abdominal mass measuring 24 cm in diameter and weighing 8 kg. The mass contained necrotic debris, a cloudy fluid, hair, and cartilage. It was adherent to the small intestine in an area associated with focal thickening of the cystic wall of the mass. Histologically, the mass demonstrated a MCT within which arose a well-differentiated squamous cell carcinoma. At the point of attachment to the small intestine, histologic sections demonstrated a transmural invasion of the squamous cell carcinoma into the attached segment of the small intestine through the muscularis propria and the submucosa reaching the mucosal surface. Thirteen regional lymph nodes were isolated near the portion of the small intestine involved with the tumor; however, none of them exhibited metastatic carcinoma.