Lipomas of the Oral Cavity: Utility of MDM2 and CDK4 in Avoiding Overdiagnosis as Atypical Lipomatous Tumor

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From: Head and Neck Pathology(Vol. 13, Issue 2)
Publisher: Springer
Document Type: Report
Length: 411 words

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Byline: Ivan J. Stojanov (1,2), Adrian Marino-Enriquez (3), Nacef Bahri (3), Vickie Y. Jo (3), Sook-Bin Woo (4,5) Keywords: Lipoma; Atypical lipomatous tumor; Liposarcoma; Well-differentiated liposarcoma; Immunohistochemistry; FISH Abstract: Traumatized lipomas with degenerative change may demonstrate histopathologic features that mimic atypical lipomatous tumor (ALT). Previously reported series of ALT involving the oral cavity preceded routine use of MDM2 and CDK4 immunohistochemistry. Our aim is to evaluate MDM2 and CDK4 immunohistochemical expression in adipocytic tumors arising in this site, in conjunction with the histiocytic marker PU.1, to determine whether MDM2 and CDK4 impacts classification. 17 cases originally diagnosed as ALT were retrieved and immunohistochemical studies for MDM2, CDK4 and PU.1 were performed. FISH analysis for MDM2 amplification was performed in select cases. For this study group, the male:female ratio was 9:8 and the median age was 62 (range 41--88). All 17 cases presented as well- or predominantly well-circumscribed proliferations of variably sized, mature adipocytes exhibiting uni- or multi-vacuolation with occasional scalloped nuclei and mild nuclear atypia. Variable amounts of fibrous stroma with focal myxoid change and bland spindle cells were identified in 14/17 cases. Lipoblasts or atypical hyperchromatic stromal cells were not identified in any cases. 14 of 17 cases were negative for MDM2 and CDK4 in tumor cells and 11 of these 14 showed weak nuclear positivity for MDM2 in histiocytes. 3 of 17 cases showed weak, multifocal immunohistochemical expression of MDM2 and CDK4. PU.1 highlighted histiocytes in all 17 cases. FISH analysis for MDM2 amplification was negative in all 3 cases with weak MDM2/CDK4 expression. All cases were reclassified as lipoma with degenerative changes. ALT, in all likelihood, is less common than previously thought in this anatomic location and best diagnosed with ancillary studies. MDM2 expression in histiocytes is best interpreted in conjunction with CDK4 immunohistochemistry and confirmatory FISH for MDM2 amplification. Author Affiliation: (1) 0000 0001 2164 3847, grid.67105.35, Department of Oral and Maxillofacial Medicine and Diagnostic Sciences, Case Western Reserve University School of Dental Medicine, Cleveland, OH, USA (2) 0000 0001 2164 3847, grid.67105.35, Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA (3) 0000 0004 0378 8294, grid.62560.37, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA (4) 000000041936754X, grid.38142.3c, Department of Oral Medicine, Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA (5) Center for Oral Pathology, StrataDx, Lexington, MA, USA Article History: Registration Date: 04/05/2018 Received Date: 18/01/2018 Accepted Date: 04/05/2018 Online Date: 10/05/2018

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Gale Document Number: GALE|A585363584