Multiple primary malignant tumours of lung and colorectal adenocarcinoma: A case report

Multiple primary malignant tumors of lung and colorectal incidence were extremely rare and in most cases, diagnosed incidentally. Due to its rarity, most physicians consider pulmonary lesions found in patients with a history of colorectal cancer as lung metastasis. To avoid misdiagnosis and treatment delays, it is critical to properly screen and explore for possible metastasis or the occurrence of a second primary tumor after a primary cancer has been diagnosed. We describe a 72-year-old woman who presented with rectal bleeding associated with altered bowel movement. Rectal biopsy revealed colon adenocarcinoma and subsequent CT scan showed sigmoid colon mass and right lower lobe lung mass with multiple mediastinal lymphadenopathies. Biopsies of the mediastinal lymph nodes also showed adenocarcinoma. PET/CT scans showed different SUVmax of lesions in the sigmoid colon and right lower lobe, which raised the possibility of separate colonic and lung primary tumors as opposed to colonic primary with lung metastasis. Further immunohistology studies confirmed separate primary lung tumor. These diagnoses facilitate the clinical approach and define treatment options for the patient.