Cytological features of NUT midline carcinoma arising in sino-nasal tract and parotid gland: Report of two new cases and review of the literature.

Nuclear Protein in Testis (NUT) Midline Carcinoma (NMC) represents a recently described, uncommon, high-grade and extremely lethal malignancy mainly occurring in children and young adults. Such tumors are genetically characterized by chromosomal rearrangements of the NUT gene. Cytological description of NUT carcinoma is limited and only seven cases were reported up to date. We show here another two cases studied cytologically with molecular and immunohistochemical confirmation. In both cases smears were hypercellular and composed of isolated or clustered small to medium-sized in size with roundish and oval shape cells. Nuclei were either regular or roundish containing dusty chromatin and prominent nucleoli. Mitotic figures were prominent. Cytoplasm was scant, strongly basophilic. Cell debris, necrosis, and apoptosis were also prominent. One of the cases was studied by FISH and the second case was studied by RT-PCR and BRD4-NUT translocation was found in both cases. Moreover, the clinical evolution was aggressive in both cases with rapid fatal clinical outcome. NUT carcinomas are an underdiagnosed entity which should be taken into consideration when poorly differentiated carcinomas was diagnosed in children or young adults. Cytology material may be successfully used for morphological and molecular diagnosis. Diagn. Cytopathol. 2016;44:753-756.