Laryngopharyngeal Liposarcoma: A (Somewhat Docile) Wolf in Sheep's Clothing.

BACKGROUND: Adipocytic tumors of the head and neck are mostly benign, but laryngopharyngeal tumors are uncommon and poorly characterized. We compared the clinicopathologic profile of laryngopharyngeal liposarcomas (LP-LPS) and lipomas (LP-L) across two institutions. DESIGN: Head and neck adipocytic tumors were queried for LP-LPS and LP-L. Demographic, pathologic, immunophenotypic features (including MDM2 amplification status), treatment and outcomes were reviewed. RESULTS: LPS constituted 1.4% (n = 22/1584) of head and neck adipocytic lesions with a disproportionate representation at laryngopharyngeal sites in both cohorts (8/19, 42.1%; 2/3, 66.7%). LPS comprised a higher proportion of laryngopharyngeal tumors as compared to other site groups (8/18, 44.4%; 2/2, 100%). Adding personal consult cases yielded 12 LP-LPS and 10 LP-L. Only atypical hyperchromatic cells, and MDM2 status differed significantly between groups (adjusted p = 0.037 and < 0.001 respectively). Recurrences were more frequent in LP-LPS (6/11, 54.5%) than LP-L (1/8, 12.5%) with a median disease-free survival of 83.5 months for LP-LPS. Most LP-LPS (10/12, 83.3%) were well differentiated liposarcomas (WDLPS) with two being dedifferentiated liposarcomas (DDLPS). Six of 10 LP-L were conventional while 4 were spindle cell lipomas (SCL). Only 2/10 (20%) of the WDLPS were initially diagnosed as such, with SCL being the most common initial diagnosis (3/10, 30%). Two cases (20%) had prominent angiomatous change. The sclerosing subtype predominated (n = 8/12, 66.7%) often SCL-like. One DDLPS had a pleomorphic rhabdomyosarcoma component while the other was an undifferentiated pleomorphic/spindle cell sarcoma. CONCLUSION: Head and neck LPS are rare but disproportionately represented at laryngopharyngeal sites both as a proportion of head and neck liposarcomas and proportion of adipocytic tumors by site. LP-LPS share similarities to LP-L, and are easily mistaken for SCL, inflammatory or vascular lesions. While atypical hyperchromatic cells are discriminatory between LP-LPS and LP-L, MDM2 status is more robust and strongly recommended when encountering an adipocytic (particularly SCL-like) or otherwise unclassifiable fibroinflammatory/vascular lesion in laryngopharyngeal sites. LP-LPS tumors often recur locally but are more indolent and somewhat less prone to dedifferentiation than their retroperitoneal counterparts.