Clinical history: 49 year old female with unilateral ovarian mass.
What is the most probable diagnosis?
High grade serous carcinoma
The tumor consists of micropapillary and branching papillary fronds, with stratification and slit-like fenestrations, glandular complexity with solid sheets, moderate to marked nuclear atypia with marked pleomorphism, prominent nucleoli, and frequent mitoses. Variable psammoma bodies are identified. The stroma is variable between desmoplastic and edematous in some areas. Wide spread stromal invasion is present.
High grade serous carcinoma is distinguished from low grade serous carcinoma by having more complex growth patterns, marked nuclear atypia with prominent nucleoli, and frequent mitoses, and wide spread stromal invasion. Psammoma bodies characterize serous tumour, but are not specific for neoplasia. The differential diagnosis includes other ovarian epithelial tumors that have papillary architecture like endometrioid and clear cell carcinoma. The papillary fronds present in some endometrioid carcinoma have a more vilous character, usually longer and more regular than those present in serous tumors, and are lined by more columnar cells in addition to association with squamous differentiation. The slitlike luminal spaces and presence of psammoma bodies are in favour of serous tumor. In clear cell carcinoma, the papillae frequently have a ramifying, anatomising network of hylinized stromal cores and are lined by atypical clear and hobnail cells. Mesothelioma and metastatic adenocarcinoma to the ovary are also included in the differential diagnosis. Multiple foci of ovarian surface tumor and extensive lymphovascular invasion are in favour of metastatic carcinoma.
The tumor cells are diffusely and strongly positive for CK7, PAX-8, P53, CA125, and WT-1, variably positive for ER and negative for vimentin and PR. Endometrioid carcinoma is positive for ER, PR, and vimentin and negative for WT1. Clear cell carcinoma is frequently negative for ER and WT1. Mesothelioma is negative for CA125. This immunoprofile supports an ovarian origin and is consistent with a high grade serous carcinoma.