Salivary duct carcinoma and small cell carcinoma ex-pleomorphic adenoma: A heretofore undescribed entity and the naming conundrum: MiNEN, combined, collision, or composite tumor?

Carcinoma with dual neuroendocrine and non-neuroendocrine components are recognized albeit a rare occurrence among the head and neck tumours. Owing to a disjointed pathology taxonomy and a lack of defining criteria, these tumors have remained underrecognized and poorly understood by pathologists and oncologists. Herein, we present a heretofore unreported case of a mixed neuroendocrine non-neuroendocrine carcinoma occurring as a carcinoma ex-pleomorphic adenoma (CXPA) in the soft palate of a 32-year-old man. Histologic examination revealed 2 distinctive malignancies comprising salivary duct carcinoma (SDC) and small cell carcinoma (SmCC) arising in a background of a benign pleomorphic adenoma. On immunohistochemistry, the SDC cells were cytokeratin 7 positive, androgen receptor positive, GATA-3 (GATA binding protein 3) positive, and gross cystic disease fluid protein (GCDFP-15) positive and the SmCC cells were synaptophysin positive and chromogranin positive, confirming the presence of 2 different histologic malignancies. We report this case not only for its exceptional rarity but also to discuss the lacunae that exist in the current classification systems that might facilitate an erroneous categorization of these rare tumors. Standardization of nomenclature and defining criteria is imperative to ensure accurate diagnosis, optimal management, and a better understanding of the biology of these enigmatic tumors.