NATIVE PULMONARY MUSCULAR PROLIFERATION

Four cases with native pulmonary muscular proliferation (NPMP) are rep orted. The etiology of this rare condition is unknown. A hamartomatous process is discussed. In spite of its rarity the correct diagnosis of this condition is important. Both clinically and histologically in tr ansbronchial biopsies, NPMP may be mistaken for pulmonary lymphangiole iomyomatosis (PLAM). Distinction of these 2 conditions is adamant, as PLAM has a poor prognosis, and, moreover may be associated with genera l disease, as with tuberous sclerosis. Whereas the typical distributio n of more mature desmin positive muscle cells in a dense center core a nd more immature desmin negative radiating peripheral muscle cell prol iferation with fascicular pattern in NPMP may be recognized in open lu ng biopsy, these differences may not become evident in small transbron chial biopsies. Immunohistochemical methods play an important role in the differential diagnosis - as with PLAM estrogen and progesterone re ceptors may be expressed and, most importantly, the reaction of the HM B45-antibody appears consistently positive in muscle cells of PLAM, wh ile negative with NPMP. Thus, recognition of this clinically innocent disease is also possible in small tissue particles.