Extrapulmonary lymphangioleiomyomatosis (LAM): Clinicopathologic features in 22 cases

We describe the lesions of extrapulmonary lymphangioleiomyomatosis (LAM) af fecting the lymph nodes of the mediastinun and retroperitoneum in 22 women (mean age +/- SD, 42.4 +/- 10.5 years). In most of these patients, the diag nosis of extrapulmonary LAM preceded that of pulmonary LAM, usually by 1 to 2 years. Eleven patients had distinct symptoms, including chylous pleural effusion and/or ascites, abdominal, pain, and palpable abdominal masses. In the other 11 patients, the masses caused no symptoms. Well-circumscribed, encapsulated masses, measuring up to 20 cm in size, occurred in the mediast inum in 2 patients, the upper retroperitoneum in 15, extensive areas of the retroperitoneun in 2, and the pelvis in 3. The masses exceeding 3 cm in di ameter contained large, multiple cysts filled with yellow-tan chylous fluid . Histologically, the masses were characterized by a proliferation of smoot h muscle cells (LAM cells) arranged in fascicular, trabecular, and papillar y patterns, which were associated with slit-like vascular channels. The LAM cells varied from small, spindle-shaped cells to large epithelioid cells. Immunohistochemical studies showed a strong reactivity of most LAM cells fo r alpha -smooth muscle actin and smooth muscle myosin heavy chain and a wea k to moderate reactivity of a lesser number of cells for desmin and nonmusc le myosin heavy chain II-B. A reaction for HMB-45 and estrogen and progeste rone receptors was observed mainly in epithelioid LAM cells. These patterns of reactivity are similar to those observed in pulmonary LAM. However, the chylous cysts are not a feature of pulmonary LAM and are thought to result from obstruction of lymphatics. HUM PATHOL 31:1242-1248. Copyright (C) 200 0 by W.B. Saunders Company.