Sarcomatoid or anaplastic carcinomas arising within epithelial ovarian neoplasms are rare, particularly within serous skin oil tumors of the ovary, and carry a poor prognosis.Here we present the case of a patient initially diagnosed with low grade serous ovarian carcinoma arising within a serous borderline tumor (atypical proliferative serous tumor).She underwent rapid progression of disease and Creams was found to have anaplastic/sarcomatoid carcinoma on biopsy of recurrence.These findings prompted pathologic re-review of the original neoplasm, which demonstrated a microscopic focus of sarcomatoid/anaplastic carcinoma.