Malignant degeneration of benign cystic teratoma of the bilateral ovaries: adenosquamous carcinoma in the right tumor and squamous carcinoma in the left tumor.

An extremely rare case of malignant degeneration arising separately in benign cystic teratoma of the bilateral ovaries is reported in a 51-year-old woman. The solid part of the right tumour consisted basically of squamous cell carcinoma, but had a small area of adenocarcinoma, whereas the solid part of the left tumour consisted of squamous cell carcinoma. It was found that in both the cystic teratomas, squamous cell carcinoma had developed separately from the columnar epithelium by a process of squamous metaplasia and malignant change in situ. It is suggested that these malignant degenerations of benign cystic teratoma of the bilateral ovaries had occurred independently due to local carcinogenic agents in the constituents of each cyst content.