Endometriosis is a common condition in reproductive age women that is defined as the presence of endometrial tissue (epithelial and/or stromal) outside the uterine corpus. While not a premalignant lesion, it is a condition with a potential for malignancy, especially in the ovaries. Notable endometriosis-associated neoplasms include clear cell carcinoma and endometrioid adenocarcinoma of the ovaries. There have been recent reports of mesonephric-like adenocarcinoma (MLA) of the ovary, a very rare neoplasm with similar morphologic and immunophenotypic characteristics as mesonephric adenocarcinoma, however, without an association with mesonephric remnants. Some of these cases have been associated with endometriosis. Here, we describe 2 cases of MLA arising directly from endometriosis. In both cases, there was evidence of endometriosis contiguous with the tumor and invasion from other sources was excluded. The immunophenotypes of both tumors were typical of mesonephric adenocarcinoma except PAX-8 was strongly positive suggesting a Mullerian origin. Molecular testing on one of the cases revealed KRAS and P53 mutations. We review published findings of MLA and associated endometriosis. This report describes the sixth and seventh reported cases of MLA associated with endometriosis and the first reported cases of MLA arising directly from endometriosis and associated with other forms of epithelial proliferation within endometriosis. These 2 cases provide potential evidence that MLA should be considered an endometriosis-associated neoplasms.
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