NSD3-NUT-expressing midline carcinoma of the lung: first characterization of primary cancer tissue.

BACKGROUND: Nuclear protein in testis (NUT) midline carcinoma (NMC) is a rare, aggressive malignancy. Only two pediatric and three adult cases of pulmonary NMCs have been documented. In more than two-thirds of NMC cases, a gene fusion between NUT and BRD4 or BRD3 has been documented; other fusions are rare.

CASE PRESENTATION: A 36-year-old woman was admitted because of a rapidly progressing tumor of the lung with metastases to the breast and bone. A biopsy from the lung tumor revealed an undifferentiated neoplasm exhibiting round to oval nuclei with vesicular chromatin, prominent nucleoli, and scant cytoplasm. Immunohistochemical staining demonstrated focal EMA, cytokeratin AE1/AE3, cytokeratin CAM 5.2, p63, CD138, and vimentin positivity. Finally, the nuclear staining pattern for NUT confirmed a histopathological diagnosis of NMC. A 5'- rapid amplification of the cDNA end (RACE) procedure successfully identified the partner of the NUT translocation as NSD3, a recently discovered partner. Fluorescence in situ hybridization confirmed the NSD3-NUT gene rearrangement, whereas a BRD3/4-NUT fusion gene was not detected.

CONCLUSION: We herein describe the first case of an NSD3-NUT-expressing NMC of the lung. The further accumulation of variant NMCs should provide clues to the establishment of new individualized therapy for NMCs.