[Primary lung salivary gland-type duct carcinoma: a clinicopathological analysis of two cases and review of literature].

To investigate the clinicopathological features, diagnostic criteria and differential diagnosis of primary salivary gland-type duct carcinoma of lung(LSDC). Two patients with LSDC after surgical resection in Shanghai Pulmonary Hospital from 2020 to 2021 were included; their clinical parameters as well as pathological, immunohistochemical and molecular characteristics of the tumors were analyzed. The relevant literature was also reviewed. Both patients were male, aged 49(case 1) and 64(case 2) years, respectively, and with a history of smoking. The chest computed tomography scan showed both lesions to be centrally located. Gross examination showed the maximum diameters were 16 mm and 35 mm, respectively. The histomorphology of LSDC resembled ductal carcinoma of breast, with intraductal islands of neoplastic cells, which also formed solid nests, papillary, micropapillary and cribriform structures. There was frequent accompanying comedo-like necrosis. The neoplasm cells were markedly heteromorphic, possessing large irregular nuclei with prominent nucleoli, abundant eosinophilic or clear cytoplasm, and mitotic figures were common. Both cases of LSDC were immunoreactive for CKpan, CK7, AR, HER2 staining was (2+) and were negative for TTF1, Napsin A, p40, GATA3, mammaglobin, GCDFP15, SOX10, PSA, P504S, ER, PR, vimentin, S-100, SMA, CK5/6 and p63. The tumor showed double-layer cell structure of the duct, and some basal cells/myoepithelial cells expressed p40 and CK5/6. Case 1 had no gene mutation while case 2 harbored TP53 and KMT2A gene mutation detected by next generation sequencing. LSDC is a very rare and highly aggressive salivary-type malignant tumor. The postoperative diagnosis mainly depends on histopathology and immunohistochemistry, attention should be paid to differential diagnosis to prevent missed diagnosis.