Bronchial salivary gland-type intraductal carcinoma with KIAA1217::RET gene fusion composed of intercalated and oncocytic components.

Salivary gland-type intraductal carcinoma (IC) is a rare malignant salivary gland neoplasm. Primary salivary gland-type IC has never been described in the lung. Herein, we present a primary pulmonary IC in a 63-year-old woman. The tumor originated in the bronchus wall of the right middle lobe. The tumor consisted of two histological types, intercalated component and oncocytic component. The intercalated component showed tubular/cystic pattern composed of column to cube-shaped cells and scattered mucous cells. The oncocytic component showed solid nests composed of large cells with abundant eosinophilic granular cytoplasm. Immunohistochemically, both histological components were positive for cytokeratin 7 (CK7), S-100 protein, SOX10, and mammaglobin. The rimming myoepithelial cells were highlighted by p63 and smooth muscle actin (SMA). The tumor cells were negative for androgen receptor (AR), HER-2, Dog-1, TTF-1, napsin A, GCDFP-15, and GATA3. In the present case, we detected KIAA1217::RET fusion via DNA-based next-generation sequencing (NGS) and RT-PCR, which established the diagnosis of IC at a molecular level. The present case expands the categories of bronchopulmonary salivary gland-type tumors.