Misdiagnosis of High-grade Serous Ovarian Cancer With BRCA Mutation as Endometriotic Cyst Due to Its Unique Gross Morphology: A Case Report and Literature Review.

It is believed that high-grade serous ovarian cancer (HGSOC) is a solid or multilocular-solid cancer. Here, we report the case of a 40-yr-old woman with a left ovarian unilocular cyst. Ultrasonography and computed tomographic examination confirmed that the cyst was thin-walled and homogenous in thickness without mural nodules. It was considered to be an endometriotic cyst. Left ovarian cyst excision specimens proved it to be HGSOC after pathologic examination. Therefore, the patient underwent radical surgery for HGSOC. Pathologic examination of radical resection specimens confirmed that the HGSOC was still in FIGO stage IA and no fallopian tube lesion was found. Considering that the patient had a history of breast cancer in both the breasts at a young age, it was hypothesized that the breast cancer susceptibility gene (BRCA) gene may have a germline mutation. Next-generation sequencing confirmed the BRCA1 (c.3770_3771delAG) germline mutation in this patient. Previous studies have reported the special morphological characteristics and growth pattern of HGSOC with BRCA mutation in the advanced stage. Our case demonstrates that HGSOC with the BRCA mutation can also be a unilocular cyst with a thin wall and uniform thickness without a mural nodule, and in the early stage, may have unique gross morphology.