The invasive component of a low-grade serous carcinoma (LGSC) consists of isolated tumor cells, small glands and irregular nests infiltrating desmoplastic stroma. In addition, there may be micropapillae or macropapillae surrounded by lacunar spaces. Psammoma bodies are a frequent finding (as seen here). The presence of stromal invasion distinguishes LGSC from serous borderline tumor (SBT). The immunohistochemical profile of LGSC is similar to SBT – they express CAM5.2, AE1/AE3, EMA, Ber-EP4, WT1, and PAX8. ER and PR are usually strongly positive (PR positivity seen in about 50% of cases). TP53 is wild type (unlike high-grade serous carcinomas). Ki-67 proliferation index is low. Prognosis of organ-confined LGSC is excellent with surgical therapy. Advanced stage tumors pursue an indolent course and respond poorly to conventional platinum-based chemotherapy. The 5-yr and 10-yr survival rates are 85% and 50%, respectively.