Triple primary cancer with concurrent detection of two tumor components in a lung biopsy specimen: a case report

Multiple primary cancers (MPCs) are uncommon, and triple primary cancers are particularly rare. Their diagnosis and treatment are challenging because they can be mistaken for recurrence or distant metastasis, resulting in missed or incorrect diagnoses. A 70-year-old Chinese man underwent right nephrectomy for clear cell renal cell carcinoma 21 years earlier. Six years before the current presentation, chest computed tomography (CT) and biopsy of a left lung lesion confirmed pulmonary metastasis of clear cell renal cell carcinoma. A complete response (CR) was achieved after 6 months of combined immunotherapy and targeted therapy. Two years before presentation, melena led to the diagnosis of sigmoid colon cancer, for which radical resection was performed. Eleven months before the present report, follow-up imaging revealed hepatic and pulmonary lesions. CT-guided percutaneous lung biopsy identified both lung adenocarcinoma and clear cell carcinoma within the same specimen. Liver biopsy confirmed metastatic clear cell renal cell carcinoma. The patient subsequently received combined immunotherapy and chemotherapy and remained in a generally stable condition. This rare collision tumor required detailed pathological and radiological assessment for diagnosis. Reporting such cases may improve understanding of tumor behavior and support the development of evidence-based diagnostic and treatment strategies.