Retroperitoneal epithelioid angiomyolipoma leading to fatal outcome

Epithelioid angiomyolipoma (AML) is a newly established variant of AML, characterized by monomorphous epithelioid cells that show HMB-45 immunopositivity, and it often displays aggressive behavior. To date, they have mostly appeared in the kidneys; however, the present autopsy case of a 43-year-old female without the stigmata of tuberous sclerosis complex had a huge retroperitoneal mass, accompanied by involvement of the regional lymph nodes. Histopathologically, the tumor was composed of round, polygonal or short spindle-shaped monomorphous cells with abundant eosinophilic cytoplasm and large nuclei with frequent multinucleation. Mitotic figures were scattered. Mature fat cells and thick-walled abnormal blood vessels were totally absent. Immunohistochemically, the tumor cells were reactive with HMB-45 and alpha-smooth muscle actin antibodies. In spite of curative surgery and repeated radio- and chemotherapy, the tumor continued to grow and brought about the patient's death 4 years after the initial symptoms. At autopsy, the peritoneal cavity was filled with the tumor mass exceeding 5.5 kg. Histopathological features were essentially the same as those of biopsy samples, but the cellular pleomorphism and emperipolesis were more easily identified. This report calls attention to this unusual manifestation of AML in the retroperitoneum and the importance of distinguishing it from sarcomas and/or paragangliomas.