Nuclear protein of the testis midline carcinoma in the oral cavity: retrospective review of those initially diagnosed as poorly differentiated squamous cell carcinoma using an anti-C52B1 antibody.

Nuclear protein of the testis (NUT) midline carcinomas (NMC) are malignant epithelial tumours that have chromosomal rearrangements of the gene encoding NUT at 15q14. NMC is typically an aggressive fatal cancer, clinically overlaps with other carcinomas, and differential diagnosis is difficult. The purpose of this study was to investigate NMC in poorly differentiated oral squamous cell carcinoma (OSCC) with a retrospective analysis based on anti-C52B1 immunohistochemical staining. An anti-C52B1 antibody was used for immunohistochemical staining in all 27 primary tumours, and the prevalence and pathological features of NMC in the oral cavity were examined. Only two of 27 cases (7.4%) were C52B1 immunopositive. Both positive patients were women aged 38 and 43 years - younger than the other C52B1-negative patients, whose average age was 65.6 years (range 41-83). The primary sites were the right side of the floor of the mouth and the left side of the tongue. They had a poor prognosis and died within 8 months postoperation compared with the median overall survival time of 60.2 months for patients with other poorly differentiated squamous cell carcinoma. The pathological findings of their primary tumours were similar to typical poorly differentiated OSCC.