Endobronchial Lipomatous Tumors

Lipomatous lesions rarely involve the bronchial tree, and detailed morphologic and molecular cytogenetic analysis of these tumors is lacking. The clinicopathologic features of 12 endobronchial lipomatous neoplasms were studied, with ancillary fluorescence in situ hybridization performed in subsets of cases for CPM, which is amplified in atypical lipomatous tumorswell-differentiated liposarcomas (ALTWDL), and HMGA1and HMGA2, which are often rearranged in lipomas. The cases occurred predominately in older men (91) (age range 44 to 80 y, mean 65 y). Most patients (80) had a former or current history of heavy smoking (20 to 100 pack-years). Three patients had concurrent pulmonary squamous cell carcinoma, and 1 had a history of multiple lung cancers. Most lesions were small (<2.5 cm) and discovered incidentally. A subset of tumors showed atypical morphologic features that would be suggestive of ALTWDL in soft tissue sites, including regions of fibrosis and scattered hyperchromatic stromal cells. However, all cases with atypia were CPMnegative and behaved in a clinically benign manner. Seven cases were tested for HMGA1and HMGA2rearrangement; 4 showed HMGA2rearrangement, and 1 showed HMGA1rearrangement, consistent with lipomas. Two cases were negative for HMGA12rearrangements. We conclude that endobronchial lipomatous neoplasms represent lipomas, even in the presence of morphologic features suggestive of ALTWDL. Ancillary fluorescence in situ hybridization testing may be very valuable in the analysis of these rare tumors, as true ALTWDL seem to be very rare or nonexistent at this anatomic site.