The development of ovarian carcinosarcoma from serous tubal intraepithelial carcinoma: an immunohistochemical case report with literature review.

Ovarian carcinosarcoma (OCS) is an uncommon and highly aggressive subtype of ovarian carcinoma characterized by the simultaneous occurrence of two malignant components: carcinomatous and sarcomatous. Located at the fimbrial region of the fallopian tube, serous tubal intraepithelial carcinoma (STIC) represents a form of precursor lesion for high-grade serous carcinoma (HGSC). In the current report, we present an intriguing case study of left OCS concomitant with ipsilateral STIC. Immunohistochemical (IHC) assessment showed a similar staining pattern of the carcinomatous OCS component and STIC. In conclusion, the development of OCS from STIC should be considered. Such a situation represents both a rare phenomenon and a challenge for preoperative diagnostic protocol. A careful application of selected IHC markers, p53 and Ki-67 in particular, may substantially help not only in the differential diagnosis but also in clinicopathological algorithms based on OCS molecular profiling into HGSC-like and non-HGSC-like variants.