[Clinicopathological characteristics, MSI and K-ras gene mutations of double primary malignancies associated with colorectal cancer].

To investigate the clinicopathological characteristics, MSI and K-ras mutation of double primary malignancies (DPM) associated with colorectal cancer (CRC). From January 2015 to December 2016, the clinicopathological data of CRC patients treated by surgery in the Affiliated Drum Tower Hospital of Nanjing University Medical School were collected, and the clinical data was analyzed. Multiplex real-time fluorescence quantitative PCR and amplification refractory mutation was performed to identify MSI and K-ras gene mutations. Of all patients with CRC, 5.2% (55/1 066) were DPM. There was no significant difference in the male and female ratio, age, colorectal cancer site, T stage, N stage composition ratio between DPM patients with CRC and patients with single CRC (0.05). There were significant difference of TNM stage between the two group (0.05). The most frequent location of CRC was the colon in both DPM patients with CRC and patients with single CRC[35.5% (359/1 011) and 41.8% (23/55), respectively]. Of 55 DPM patients with CRC, 48 were metachronous DPM patients, 7 were synchronous DPM patients and 41 were colorectal cancer first. In extracolonic organ, digestive system (23/55) was the most commonly occurring system and stomach (11/55) was the most common lesion. DPM patients with CRC had higher incidence of MSI-H than patients with single CRC (0.05). There was no significant difference of K-ras gene mutation between DPM patients with CRC and patients with single CRC (0.05). MSI-H and K-ras mutation were present in only 2 patients of DPM patients with CRC. The rectum is the most common lesion site in CRC patients. The stomach is the most common extracolonic organ of DPM patients with CRC. DPM patients with CRC has high risk of MSI-H, but no significant difference in the incidence of K-ras mutation.