Morphological features and genetic background in ectomesenchymal chondromyxoid tumor: A systematic review.

Background: Ectomesenchymal chondromyxoid tumor (EMCMT) is a rare neoplasm that mainly affects the tongue and harbors recurrent, although not exclusive, gene fusions. Owing to its rarity, overlapping features with other tumors may lead to challenges in the microscopic diagnosis. We aimed to perform a systematic review focusing on the histomolecular findings of EMCMT of the oral and maxillofacial region and to evaluate the possible association between microscopic features with the genetic background.

Methods: An electronic search was made on PubMed, Web of Science, Scopus, Ovid, and Embase. Clinicopathological, immunohistochemical, and molecular data were retrieved.

Results: Overall, 114 cases from 53 articles on EMCMT were analyzed. Histologically, EMCMT was described as demarcated (84.2%), lobulated (66.7%), reticulated (51.8%), and arranged in sheets, cords, and strands (42.9%), with 73.7% of lesions with spindle-shaped cells. Myxoid stroma (88.6%), chondroid areas (60.5%), chondromyxoid stroma (57.0%), and fibrous septae (42.9%) were also tumor-outlined features. The most expressed markers were vimentin (100.0%), cyclin D1 (100.0%), GFAP (88.5%), NSE (87.5%), S100 (86.5%), CD56 (76.9%), and CD57 (76.5%). The RREB1-MRTFB fusion was detected in 91.0% of the cases investigated and EWSR1 rearrangements in 17.4%. The presence of the fusion RREB1::MRTFB or chromosome alterations in the EWSR1 gene were not highly specific to the morphological features of EMCMT.

Conclusion: This study provides a comprehensive summary of the clinicopathological, immunohistochemical, and molecular characteristics of EMCMT, aiding in a more accurate microscopic diagnosis of this rare tumor.