Original ArticlesExpanding the Spectrum of Microscopic and Cytogenetic Findings Associated With Spitz Tumors With 11p GainsLezcano, Cecilia M. MD*; Yeh, Iwei MD, PhD†; Eslamdoost, Nasrin BS, MA*; Fang, Yuqiang MS*; LeBoit, Philip E. MD†; McCalmont, Timothy H. MD†; Moy, Andrea P. MD*; Zhang, Yanming PhD*; Busam, Klaus J. MD* Author Information *Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, NY †Dermatopathology Section, Department of Pathology and Dermatology, University of California, San Francisco, CA Conflicts of Interest and Source of Funding: Supported in part by the Cancer Center Support Grant of the National Institutes of Health/National Cancer Institute under award number P30CA008748. The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Klaus J. Busam, MD, Department of Pathology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, New York 10065 (e-mail: [email protected]). The American Journal of Surgical Pathology: February 2021 - Volume 45 - Issue 2 - p 277-285 doi: 10.1097/PAS.0000000000001607 Buy Metrics Abstract A subset of Spitz tumors is associated with a copy number increase of chromosome 11p and activating mutations of HRAS. These aberrations have been reported to occur in association with desmoplastic Spitz nevi. Little is known to what extent 11p gains can also be found in nondesmoplastic tumors. To learn more about the spectrum of microscopic and cytogenetic changes that can be seen in Spitz lesions in association with 11p gains, we reviewed the clinical and pathologic features of 40 cases. Patient ages ranged from 3 to 75 years. The most common anatomic site was the head and neck region, followed by the upper extremities. Prominent desmoplasia was present in 10 cases. Seven tumors lacked significant stromal fibrosis. Twenty tumors were mitotically active. Novel microscopic features encountered in a few cases include a tumor with a polypoid silhouette and papillomatous surface and rare atypical tumors with a deep bulbous growth pattern. Among 36 cases analyzed by single-nucleotide polymorphism array or comparative genomic hybridization, 28 tumors had gains of the entire or near-entire p-arm of chromosome 11 with no other coexisting unbalanced genomic aberration. Eight cases had additional changes; 6 of these with 1 additional aberration per case, and 2 cases had several chromosomal aberrations. We also examined a subset of tumors by fluorescence in situ hybridization for the HRAS gene locus (11p15.5). All tumors were fluorescence in situ hybridization–positive. In conclusion, we expand the spectrum of pathologic findings associated with Spitz tumors with 11p gains. This cytogenetic aberration is not restricted to desmoplastic Spitz nevi. It can also be seen in nondesmoplastic and papillomatous lesions and atypical melanocytic tumors with a deep bulbous growth. We also document that in some Spitz tumors additional cytogenetic aberrations may be found, the significance of which remains to be determined. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.