The clincopathological variables to differentiate the nature of isolated pulmonary nodules in patients who received curative surgery for colorectal cancer.

BACKGROUND: In colorectal cancer (CRC) patients, pulmonary nodules are usually considered lung metastases (LM). However, approximately 10% of LM is presented as a solitary pulmonary nodule which mimics primary lung cancer (PLC). This study aims to determine the distinguishing characteristics of the two pulmonary nodule types during postoperative surveillance of CRC patients.

METHODS: Between March 2009 and February 2018, 47 CRC patients with pulmonary nodules from a single institution were retrospectively analyzed. They were divided into two groups, namely CRC with second PLC (CSPLC) and CRC with LM (CRCLM), and their demographic data and clinicopathological features were analyzed.

RESULTS: When pulmonary nodules are presented, multiple lesions and serum carcinoembryonic antigen (CEA) level >5 ng/mL indicated a higher probability of CRCLM (p < 0.001 and p = 0.028, respectively). A CK7- /CK20+ /CDX2+ /TTF-1- phenotype on immunohistochemistry (IHC) stain suggested CRCLM. Other clinicopathological features showed no significant between-group differences. The median overall survival was considerably longer in the CSPLC group (not reached) than in the CRCLM group (45.41 months, p = 0.064).

CONCLUSIONS: The detection of a suspicious isolated pulmonary nodule in CRC patients warrants further workup to distinguish between SPLC and LM. Multiple lesions, serum CEA >5 ng/mL when an isolated pulmonary nodule detected, and initial TNM stage IV CRC are more likely related to LM rather than SPLC. Image-guided needle biopsy and IHC stain can reduce the probability of misdiagnosis and rule out LM. CSPLC may have a favorable prognosis owing to early detection and receiving appropriate treatment.