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4. NUT Carcinoma
Clinical Discussion
Nuclear protein in testis (NUT) carcinoma is a rare genetically defined subtype of squamous cell carcinoma notable for rapid growth and dismal prognosis (1). Median age at diagnosis of primary pulmonary NUT carcinoma is 30 years. Median survival following diagnosis is 2.2 months (2). The typical patient with primary pulmonary NUT carcinoma is previously healthy, a non-smoker, and presents with chronic cough and dyspnea (2). Males and females are affected equally. The differential diagnosis for NUT carcinoma includes other poorly differentiated and aggressive tumors, including poorly differentiated carcinoma, non-small cell lung cancer, small cell lung cancer, and high-grade neuroendocrine carcinoma.
Approximately half of NUT carcinomas occur in the thorax. NUT carcinoma has a characteristic histologic appearance and is diagnosed via immunohistochemistry and molecular genetic testing.
Radiology Discussion
Fifty percent of NUT carcinomas occur in the thorax (3). From a case series of nine patients with primary pulmonary NUT carcinomas, all tumors were centrally located, all tumors were greater than five centimeters in diameter at time of diagnosis, and 62% occurred in the right lung. In each case the primary tumor caused post-obstructive atelectasis and was accompanied by an ipsilateral pleural effusion. Notably, the contralateral lung was not involved in any case. Mediastinal adenopathy is always present. The bones are the most common site of extra-thoracic spread. In reported cases, the tumor is intensely FDG-avid (2).
Pathology Discussion
Pathology demonstrates sheets of undifferentiated cells, often with foci of abrupt keratinization (1). Tumor cells are typically p40 or p63 positive. NUT carcinoma is diagnosed via immunohistochemistry with a commercially available assay (100% specificity, 87% sensitivity) (3). In 70% of cases, NUT carcinoma is caused by a reciprocal translocation between the NUTM1 gene on chromosome 15 and the BRD4 gene on chromosome 19 (1). If available, genetic testing can be utilized to identify the BRD4-NUT oncogene.
After diagnosis, the patient was referred to the oncology service. He has since received his first round of chemotherapy, consisting of methotrexate, doxorubicin, cisplatin, and vinblastine.
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