RÉSUMÉ
BACKGROUND: Mature cystic teratoma is a common type of ovarian tumor. Although squamous cell carcinoma (SCC) is the most common carcinoma in malignant transformations of ovarian mature cystic teratomas, SCC arising in a mature teratoma is rare. METHODS: This paper reports four cases of invasive SCC, a case of an adenosquamous cell carcinoma and a case of a pure in situ SCC arising in a mature cystic teratoma including a clinicopathological evaluation and an immunohistochemical study of the p53 protein and p21WAF1/CIP1. RESULTS: The mean age of the patients was 60 years. The sizes of the mature cystic teratomas in all cases were greater than 7.5 cm in the largest diameter. Five cases showed the nuclear accumulation of the p53 protein with no p21WAF1/CIP1 immunoreactivity. The other case showed the nuclear accumulation of p21WAF1/CIP1 without p53 expression. There was a significant inverse relationship between the p53 protein level and p21WAF1/CIP1 expression. CONCLUSION: A clinicopathological evaluation showed that a SCC arising from a mature cystic teratoma must be included in a differential diagnosis when the patient is over 42 years of age and the size of a mature cystic teratoma is greater than 75 mm in the largest diameter. It is suggested that p53 overexpression is implicated in the malignant transformation, and the p21WAF1/CIP1 expression level is dependent on alterations in the level of the p53 protein in these tumors.