An aberrant mediastinal medial basal segmental pulmonary artery (A7a) in a patient with lung cancer: a case report

Background Mediastinal branching of the A7a from the right main pulmonary artery (PA) is extremely rare. Herein, we report a patient with an aberrant mediastinal A7a who underwent right basal segmentectomy for lung cancer. Case presentation A 73-year-old man was referred to our department for a right lower lobe nodule measuring 18 mm in diameter on computed tomography (CT). Three-dimensional (3D) CT revealed mediastinal A7a branching from the right main PA. As the patient had undergone colectomy for advanced ascending colon cancer, the nodule was suspected to be a metastasis from the colon primary, and thus, basal segmentectomy of the right lung was performed. Intraoperatively, the A7a was observed behind the V4+5 and middle lobe bronchus. The pathological diagnosis was combined small cell carcinoma with an adenocarcinoma component (p-T1cN0M0, stage IA3). The patient subsequently received adjuvant chemotherapy for colon cancer. At 1-year postoperative follow-up, there was no evidence of disease. Conclusion This is the first report describing an aberrant mediastinal A7a branching from the right main PA. It is important to obtain accurate information about variations of the PA using 3D-CT for safe anatomical pulmonary resection.