Mechanism of cyst formation in lymphangioleiomyomatosis

Mechanisms of airspace enlargement in LAM. Two models of airspace enlargement in LAM are presented; these may not be mutually exclusive.
(A) LAM cells secrete proteases including MMPs and cathepsin K, which degrade the extracellular matrix and induce apoptosis of alveolar epithelial cells.
(B) LAM cells express lymphangiogenic growth factors, VEGF-C and VEGF-D, which recruit lymphatic endothelial cells, drive the formation of lymphatic vascular channels, and distort the lung architecture. Original magnification, ×200.