Extrapulmonary Retroperitoneal Lymphangioleiomyomatosis Associated With Endosalpingiosis: A Case Report

Background Lymphangioleiomyomatosis (LAM) is an uncommon multisystem disorder characterized by proliferation of perivascular epithelioid cells and classified within the perivascular epithelioid cell tumor (PEComa) family. Although classically involving the lung, extrapulmonary manifestations have been documented, most frequently within the retroperitoneum and abdominopelvic lymphatics. Endosalpingiosis is a benign Müllerian lesion defined by the presence of ectopic glands lined by fallopian tube-type ciliated epithelium in the absence of accompanying endometrial-type stroma. The coexistence of extrapulmonary LAM and endosalpingiosis within the same lesion is exceedingly rare, with only a limited number of examples reported in the literature. Patient presentation A 40-year-old woman presented with abdominal distension and discomfort. Imaging demonstrated a 16-cm multilocular cyst in the right retroperitoneal space. Surgical excision was performed, and histological examination revealed a cyst with a proliferation of spindle to epithelioid smooth muscle–like cells arranged around lymphatic channels and admixed with lymphoid aggregates, consistent with LAM. The cyst wall was focally lined by ciliated columnar epithelium morphologically identical to that of fallopian tube, without associated endometrial-type stroma, in keeping with endosalpingiosis. The LAM cells exhibited positivity for PMEL (HMB-45) and desmin, whereas the endosalpingiosis component demonstrated positivity for pan-keratin and PAX8 immunostains. Conclusion Extrapulmonary LAM may rarely present as a cystic retroperitoneal lesion and coexist with endosalpingiosis, posing a diagnostic challenge. Recognition of this pattern is important to ensure correct classification and appropriate evaluation for systemic involvement.