Carcinoma-in-situ in a benign cystic teratoma of the ovary: A possible precursor of invasive squamous-cell carcinoma of the ovary

Background: Squamous carcinoma-in-situ (CIS) within a benign cystic teratoma is exceptionally rare, particularly in the absence of an adjacent invasive squamous component. Most of the few reported cases of CIS without invasive carcinomas occur in postmenopausal women and are usually incidental histopathologic findings. Case: A 35-year-old, gravida 1, para 1001, woman underwent exploratory laparotomy and bilateral ovarian cystectomies for bilateral ovarian dermoid cysts. They were excised and, via histopathology, were confirmed to be benign cystic teratomas. Six months later, the patient had pelvic pain and had a 7-cm left adnexal cyst. She underwent laparoscopic oophorectomy. The final diagnosis was invasive squamous-cell carcinoma of the ovary. A re-review of the slides of the bilateral cystectomies showed a minute focus of CIS in the right ovary that was opposite to the newer invasive carcinoma. p16 immunostaining was negative. Results: There was no evidence of malignancy or dysplasia in the sections of cyst taken from the left ovary during the original excision. Conclusions: In the absence of invasion, excision of the ovary with CIS appears to be adequate therapy. If CIS is detected histopathologically, a search for invasive elements should be undertaken.