Primary synchronous colloid adenocarcinoma and squamous cell carcinoma in the same lung A rare case report

Rationale: Double primary lung cancer (DPLC) is a relatively rare type of lung cancers. According to whether the diagnosis interval between lesions is more than 6 months, it can be divided into synchronous DPLC (sDPLC) and metachronous DPLC (mDPLC). Here, we describe a case of sDPLC in which one of the components is a rare colloid adenocarcinoma (CA). Patient concerns: A 69-year-old male was admitted to the hospital due to chest distress and shortness of breath for 1 year, getting worse in the last 15 days. Diagnosis: Both HE staining and IHC supported the diagnosis of CA in the right lower lobe and moderately differentiated squamous cell carcinoma in the right upper lobe. Interventions: The patient was treated with 3 cycles of adjuvant chemotherapy with pemetrexed and lobaplatin after the right upper lobectomy, wedge resection of the right lower lobe and lymph node dissection under video-assisted thoracoscope. Outcomes: Our plan was to follow him up with general physical examination, chest-abdomen CT and serum tumor markers every 6 months for 2 years. The patient was still alive until the last follow-up in November 2020. Lessons: CA of the lung is a rare primary lung adenocarcinoma. The diagnosis should be based on the patient's clinical characteristics, imaging examination and pathological characteristics, and also need to be differentiated from other mucinous adenocarcinomas. Interestingly, our patient developed not only a CA in the right lower lobe, but also a moderately differentiated squamous cell carcinoma in the right upper lobe.