Lymphangioleiomyomatosis: where endocrinology, immunology and tumor biology meet.

Abstract: Lymphangioleiomyomatosis (LAM) is a cystic lung disease found almost exclusively in genetic females and caused by small clusters of smooth muscle cell tumors containing mutations in one of the two tuberous sclerosis genes (TSC1 or TSC2). Significant advances over the past 2-3 decades have allowed researchers and clinicians to more clearly understand the pathophysiology of LAM, and therefore better diagnose and treat patients with this disease. Despite substantial progress, only one proven treatment for LAM is used in practice: mechanistic target of rapamycin complex 1 (mTORC1) inhibition with medications such as sirolimus. While mTORC1 inhibition effectively slows LAM progression in many patients, it is not curative, is not effective in all patients, and can be associated with significant side effects. Furthermore, the presence of established and accurate biomarkers to follow LAM progression is limited. That said, discovering additional diagnostic and treatment options for LAM is paramount. This review will describe recent advances in LAM research, centering on the origin and nature of the LAM cell, the role of estrogen in LAM progression, the significance of melanocytic marker expression in LAM cells, and the potential roles of the microenvironment in promoting LAM tumor growth. By appreciating these processes in more detail, researchers and caregivers may be afforded novel approaches to aid in the treatment of patients with LAM.