Head and neck xanthogranulomatous epithelial tumors/keratin-positive giant cell-rich tumors

Xanthogranulomatous epithelial tumor (XGET) and keratin-positive giant cell-rich tumor (KPGCT) represent ends along the spectrum of a single neoplastic entity, with overlapping clinical, morphologic, immunohistochemical, and genetic findings (XGET/KPGCT). Morphologically, they are characterized by a highly variable admixture of xanthomatous histiocytes, Touton-like giant cells, osteoclast-like giant cells, and interspersed keratin-positive cells, which may be visible on routinely stained slides as clusters of eosinophilic epithelioid cells or require immunohistochemistry for detection. Both XGET and KPGCT harbor rearrangements of HMGA2, most often with NCOR2, supporting their unitary nature. They most often occur in young adult females, may involve either soft tissue or osseous locations, and behave as mesenchymal tumors of borderline malignancy, with risk for local recurrence but little metastatic risk. Approximately 61 cases have been reported in the English literature, including 13 cases in the head and neck region. This review will summarize the known information on these neoplasms across anatomic sites and highlight diagnostic challenges unique to the head and neck region.