Tumor condromixoide ectomesenquimal: uma revisão sistemática e análise molecular de um caso extralingual

Abstract

The ectomesenchymal chondromyxoid tumor (ECMT) is a rare benign neoplasm that mainly affects the tongue and exhibits a high frequency of the RREB1-MRTFB fusion. Microscopically, ECMT resembles other chondromyxoid lesions, with myoepithelioma being one of the main differentiation challenges. Its diagnosis requires not only microscopic analysis but also immunohistochemistry. Narrative reviews on ECMT conducted so far do not encompass a systematic analysis of the literature. The RREB1-MRTFB fusion, despite being frequent in the tongue, has been tested positive in an intraosseous case, and it has not yet been described in extra-lingual oral soft tissues.Therefore, the aim of this study was to systematize the literature data with an emphasis on ECMT microscopy and report an extra-lingual case investigating the RREB1-MRTFB fusion. An electronic search across 5 databases was conducted in December 2021. A total of 44 articles comprising 101 cases of ECMT were included. Microscopically, ECMT was found to be non-encapsulated (95.5%), yet circumscribed (89.2%), exhibiting a lobular appearance (70.6%), interspersed with fibrous septa (98%), forming a solid proliferation in sheets, strands and cords (98%) in a reticular pattern (98.3%). The cells were spindle-shaped (77.5%), round and ovoid (70.6%), or polygonal (54.9%), with eosinophilic cytoplasm (34.3%), embedded in a myxoid matrix (97.0%), and chondroid (88.0%). Immunohistochemically, there was higher positivity for vimentin (100%), GFAP (88.9%), S-100 (85.7%), CD56 (76.9%), and CD57 (75%). The RREB1-MRTFB fusion occurred in n=20/23; 87,0%. The present clinical case reportes a nodule on the lingual aspect of the mandible in a 15-year-old individual, whose morphology exhibited the most frequently identified characteristics in the systematic review. The molecular analysis confirmed the diagnosis of ECMT. The present study not only contributes to a detailed understanding of the morphological diagnostic features of ECMT but also expands the molecular knowledge of the tumor based in an extra-lingual case of a Brazilian individual.