IntroductionMutations in KRAS and NRAS genes are negative predictors of anti-EGFR therapies response in metastatic colorectal cancer. There are few reports on RAS testing in synchronous primary colorectal cancer (SP-CRC) and a lack of recommendations on which tissue should be tested for the mutation in this disease. This study analyzed the RAS status of both lesions in SP-CRC patients and in their metastasis.Materials and methodsDNA was obtained from formalin-fixed-paraffin-embedded tissue, and mutations were analyzed by pyrosequencing.ResultsRAS status was heterogeneous in 6 (75%) of 8 SP-CRC patients between primary lesions. Five showed heterogeneity regarding RAS mutational status, and from these, four presented with metastasis: 3 cases (75%) had WT metastatic tissue, and 1 case (25%) had mutated metastatic tissue. One patient showed divergence regarding RAS mutation type.DiscussionRAS mutations vary significantly between SP-CRC lesions, and the status of the metastasis is unpredictable. Testing for RAS mutations in only 1 of the primary lesions can misguide clinical decisions and hind the predictive potential of anti-EGFR treatment. A more appropriate approach in metastatic SP-CRC is to test the metastatic tissue or both primary lesions for providing more accurate mutation scenery and support more assertive clinical decisions.

were in the adjuvant setting and 55.8% in palliative cases. The chemotherapy protocol depended on the histological type and was dominated by the 5FU-oxaliplatin combination in carcinomas, while the stromal tumors received TKI. After a median followup of 52.7 months, the median progression-free survival was 11.2 months and the median overall survival was 16.8 months all histological types combined. Conclusion:Malignant tumors of the small intestine pose diagnostic problems because of their scarcity and the absence of specific clinical signs. They are often operative discoveries in the event of an acute complication. The curative treatment is surgical resection regardless of the histological type. The prognosis remains reserved because of the late diagnosis of the tumor.Legal entity responsible for the study: The author.