Atypical (Symplastic) Leiomyoma Arising in Pararectal Endometriosis Associated With Metastatic Ovarian Clear Cell Carcinoma: A Case Report.

While very commonly encountered in the uterus, in particular in the wall of the uterine corpus, leiomyomas are far less frequently found in extragenital sites in females. Atypical leiomyomas (synonyms: pleomorphic leiomyomas, leiomyomas with bizarre nuclei, bizarre leiomyomas, or symplastic leiomyomas) are a rare subtype of leiomyomas, characterized by cells with bizarre, pleomorphic-appearing nuclei without (or with extremely low) associated mitotic activity. Despite the cytologic appearance, such tumors have a benign clinical course. Although there are cases of leiomyomas appearing outside the uterus in a background of endometriosis, cases specifically of atypical leiomyomas in this setting are exceptionally rare. We present a case of an atypical leiomyoma arising from pararectal endometriosis in a patient presenting with endometriosis-associated primary ovarian clear cell carcinoma, metastasis to the bladder peritoneum, and a peri-intestinal lymph node, in addition to a concurrent ovarian fibroma.