Multiple primary lung cancer comprised of adenocarcinoma and adenoid cystic carcinoma: a case report.

Background: Multiple primary lung cancer (MPLC) is a rare type of tumor, and it is necessary to differentiate it from a metastatic tumor. The type of adenocarcinoma with adenoid cystic carcinoma (ACC) is extremely rare and has not yet been reported in the literature. The initial clinical symptoms of double primary lung cancer may be nonspecific; hence, the diagnosis is often missed or incorrect. Case Description: In this case presentation, we report the case of a 67-year-old female who had experienced persistent cough and expectoration for 8 days. Chest computed tomography (CT) revealed 2 nodules in the patient's lung. Radiographic findings could not distinguish between the 2 nodules and between primary and metastatic lesions. Thus, the patient underwent bronchoscopic biopsy and percutaneous lung puncture. We could not determine the type of the two tumors in hematoxylin and eosin (H&E) staining sections, and we subsequently performed specific immunohistochemical (IHC) staining. Combined with morphological and IHC results, we concluded that this was a case of MPLC, consisting of adenocarcinoma and ACC. The patient received symptomatic treatment because of the metastases. Conclusions: This report reports a rare combination of MPLC and shows that a definitive diagnosis of double primary lung cancer can be based on tissue biopsy and IHC techniques.