Evolution of an ovarian endometriotic cyst into clear cell carcinoma with squamous differentiation across two...

Ovarian clear cell carcinoma (OCCC) during pregnancy is exceedingly rare, particularly when accompanied by squamous differentiation, with only a limited number of cases reported in the English literature to date.

A 33-year-old female, during the first pregnancy, identified endometriotic cysts. However, during the second pregnancy, the patient was subsequently diagnosed with OCCC.

In this case, histological examination reveals a tumor demonstrating tubular cystic, papillary, and solid growth patterns. Glandular areas with extensive squamous differentiation are observed, along with papillary regions containing hyalinized fibrovascular cores. Tumor cells exhibit cuboidal morphology with clear cytoplasm and hobnail appearance, showing significant atypia. The periphery demonstrates endometrial endometriosis progressing to atypical endometriosis and subsequent malignant transformation. Immunohistochemical analysis shows positive expression of P504S and NapsinA in tumor cells, thereby excluding ovarian endometrioid carcinoma. The findings are consistent with a definitive diagnosis of OCCC.

Following the detection of the ovarian mass, left adnexectomy was performed. After definitive diagnosis of OCCC, pregnancy termination was pursued, followed by total hysterectomy, right adnexectomy, and pelvic lymph node dissection.

Postoperative follow-up at 6 months revealed no evidence of recurrence.

This case highlights an ovarian cyst that measured 8 cm during the second pregnancy but was only 2 cm in diameter during the first pregnancy, ultimately diagnosed as clear cell carcinoma. Although ovarian malignancies during pregnancy are rare, benign-appearing cysts should not be overlooked. Increased vigilance is warranted to ensure timely diagnosis and appropriate management of such rare but clinically significant presentations.