Fernandes, Igor Lima

Abstract Background Intracranial mesenchymal tumors, FET::CREB fusion-positive (ICMT), show fusions involving FET RNA-binding protein family genes (EWSR1 or FUS) and CREB family of transcription factors (ATF1, CREB1, or CREM). The methylation signature(s), gene expression characteristics, and clinical behavior of this important tumor type require further characterization. Methods We study the methylation profiles of 81 ICMT cases (61 newly profiled cases and 20 cases from publicly available sources). Clinicopathologic and genomic data were recorded for each case when available. Results ICMT showed a relatively distinct methylation signature compared to related tumors. Among the 65 cases where fusion types were documented, the identified fusions included EWSR1::ATF1 (25 cases), EWSR1::CREB1 (12 cases), EWSR1::CREM (21 cases), FUS::CREM (3 cases), and SMARCA2::CREM (4 cases). We confirmed the prior description of 2 distinct subgroups of ICMT (subclasses A and B). The majority of the cases belonged to subclass A (n = 69; 85%), which showed a higher median age compared to subclass B patients (26 years vs. 15 years). Subclass B cases (n = 12; 15%) showed shorter progression-free survival (P < 0.01). Gene expression analysis of ICMT showed key overexpressed markers in ICMT, with significant CREM overexpression regardless of fusion type, when compared to either meningioma alone or a larger group of CNS tumors. Conclusions This work provides further characterization of ICMT as an important CNS mesenchymal neoplasm that is prone to tumor recurrence, showing 2 prognostically relevant methylation subclasses and warranting diagnostic distinction from other epigenetically and histologically related tumors. ICMTs show substantial overexpression of the CREM gene, independent of fusion type.

Abstract Matrix-producing tumors of the sinonasal region are diagnostically challenging, with a large number of similar-appearing neoplasms having different prognoses, treatment strategies, and genetic syndrome associations. Osteochondromyxoma (OCM) is a very rare tumor known to be associated with Carney complex. Since its initial description in 2001, fewer than 20 cases have been reported, with the sinonasal tract being an apparently favored site. Herein we describe 6 new cases of sinonasal OCM.OCM cases with available slides were retrieved from the surgical pathology files of the authors’ practices. The tumors arose in 4 boys and 2 girls, ranging from 4 to 17 years (mean, 9.5 years). All presented with nasal obstruction and a mass. Radiologically the tumors presented as indolent-appearing, heterogeneous, calcified, expansile masses. Histologically the tumors all consisted of bland, normochromatic spindled to stellate cells in a myxoid to collagenized stroma, with variable amounts of cartilage and bone formation. Mitotic activity was very low and necrosis was absent. All demonstrated complete loss of PRKAR1A expression by immunohistochemistry. Of these 6 cases, 3 had been originally diagnosed as nasal chondromesenchymal hamartomas, and one as osteosarcoma. Treatment and follow up information were available for 5 patients: all were treated with surgery, with one also receiving chemotherapy after an initial osteosarcoma diagnosis. At the time of last clinical follow-up, all 5 patients were alive, one with residual disease. No patient was known to have other stigmata of Carney complex.Although rare, OCM preferentially occurs in the sinonasal tract, and therefore may be encountered by head and neck pathologists. Given their predilection for young patients and overlapping morphologic features, OCM are easily misdiagnosed as other matrix-forming sinonasal tumors, especially nasal chondromesenchymal hamartoma. Immunohistochemical demonstration of PRKAR1A loss is valuable for confirming an OCM diagnosis, which should prompt clinical investigation for the possibility of Carney complex.