A rare Japanese case with a NUT midline carcinoma in the nasal cavity: A case report with immunohistochemical and genetic analyses

BackgroundNUT (nuclear protein in testis) midline carcinoma (NMC) is a recently described aggressive malignancy that is genetically defined by rearrangements of the NUT locus at 15q14. In approximately two-thirds of cases, the characteristic t(15;19) results in the fusion oncogene BRD4-NUT. Only 10 sinonasal NMCs have been documented, none of which were Japanese cases.Case presentationAn 18-year-old woman was admitted because of a rapidly progressing tumor in the nasal cavity. A biopsy revealed an undifferentiated neoplasm without squamous differentiation. The tumor cells had round to oval nuclei with vesicular chromatin, prominent nucleoli, and scant cytoplasm. Immunohistochemical staining demonstrated a strong positivity for vimentin and NUT, with focal CD138 and only spotty EMA and cytokeratin AE1/AE3 staining. Cytogenetic and fluorescence in situ hybridization analyses revealed a t(15;19) and BRD4-NUT gene rearrangement. Direct sequencing identified the in-frame fusion of exon11 of BRD4 with exon2 of NUT. The patient was transferred to another hospital for chemoradiotherapy.ConclusionWe herein describe the first Japanese case with an NMC of the sinonasal cavity, providing detailed and unambiguous cyto- and molecular genetic information on BRD4-NUT-rearrangement. The accumulation of cases with well-documented genetic data should provide clues to the treatment of this tumor entity.