Two cases report of secretory carcinoma of the salivary gland in the lung: one primary and one metastatic after many years.

Background: Secretory carcinoma of the salivary gland (SCSG) is a recently discovered salivary gland tumor that occurs mostly in the major salivary glands and occasionally in the skin, cervix, trachea, etc. Secretory carcinoma of the lung is extremely rare. To our knowledge, this is the third report of SCSG arising as a primary pulmonary tumor. The two SCSG cases reported in this paper are unique in that one was primary and the other was metastasized to the lung.

Case Description: Case 1 is a primary endobronchial tumor in a 66-year-old man. He went to the doctor complaining of fever, cough and yellow phlegm, and his body weight was significantly reduced by 3 kg. The bronchoscope showed the growth of new organisms in the right upper lobe of the lung. Immunohistochemistry of his biopsy specimen was positive for AE1/AE3, Keratin7 (CK7), S-100, mammaglobin, and pan-TRK, but negative for thyroid transcription factor-1 (TTF-1), napsin-A, synaptophysin (SYN), chromogranin A (CGA), and discovered on GIST-1 (Dog-1), and the MKI-67 (Ki-67) proliferation index was 2%. This case lacked the typical gene rearrangement. After one cycle of chemotherapy, the tumor was significantly reduced, and surgical excision was planned. Case 2 was a metastatic secretory carcinoma with a history of parotid pleomorphic adenoma resection 30 years ago and malignant pleomorphic adenoma resection 16 years ago before the study, respectively. He presented with a complaint of a parotid gland mass. Chest CT examination revealed a mass in the upper lobe of the left lung. The biopsy tissue of him exhibited a typical histological appearance under the microscope. Immunohistochemistry was positive for AE1/AE3, CK7, S-100, and mammaglobin; partially positive for estrogen receptor (ER) and pan-TRK; and negative for TTF-1, Napsin-A, SYN, CGA, P63, P40, and Dog-1. The Ki-67 proliferation index was approximately 3%. Fluorescence in situ hybridization (FISH) revealed gene rearrangement. After the diagnosis of SCSG, the patient underwent resection of the lung mass, and there was no recurrence of the lung after 1 month's follow-up.

Conclusions: By examining these two cases, we have a better understanding of the clinicopathological features of secretory carcinoma, which will help to improve the accuracy of pathological diagnosis.