%0 Journal Article
%T Keratin-positive giant cell-rich tumors of soft tissue with HMGA2::NCOR2 fusions.
%A Weigelt MA
%A Azzato EM
%A Habermehl GK
%A Billings SD
%A Ko JS
%A Fritchie KJ
%J J Cutan Pathol
%V 50
%N 11
%D 2023 Nov 26
%M 37496152
%F 1.458
%R 10.1111/cup.14497
%X <B>BACKGROUND: </B>Giant cell tumor of soft tissue (GCT-ST) is a rare soft tissue neoplasm that is morphologically similar to but genetically distinct from giant cell tumor of bone. A novel keratin-positive GCT-ST (KPGCT-ST) harboring HMGA2::NCOR2 fusions was recently discovered. Fewer than 30 cases have been described; herein is reported an additional seven.<BR><B>METHODS: </B>Cases diagnosed as GCT-ST were retrieved from institutional archives and consultation files. The histopathologic characteristics were assessed, and the electronic medical record was reviewed.<BR><B>RESULTS: </B>Seven tumors were identified in six women and one man with a median age of 23 years. All patients underwent excision; no recurrences or metastases were noted during a median follow-up period of 7 months. Histopathologically, the tumors were characterized by a multinodular proliferation of keratin-positive mononuclear cells with evenly admixed osteoclast-like giant cells and absent neoplastic bone. A fibrous capsule with lymphoid cuffing was frequently seen. Foamy macrophages, inflammation, hemorrhage, and hemosiderin were variably present. The HMGA2::NCOR2 fusion was detected in all cases.<BR><B>CONCLUSIONS: </B>Our findings support previously reported hypotheses that KPGCT-ST is a spectrum of the same entity as the recently described xanthogranulomatous epithelial tumor. Although follow-up data are limited, to date, KPGCT-ST appears to follow an indolent course.