Case report of metastatic colorectal cancer associated with <i>KRAS</i> A146V and A59G mutations

Abstract

In colorectal cancer (CRC) in addition to the most common mutations in the second exon of KRAS, there are rarer mutations that are not well understood as prognostic markers.Description of cases. We describe two clinical cases of moderately differentiated adenocarcinoma (low-grade, G2), which manifested a complicated course in a 67-year-old woman – intestinal obstruction (case 1) and in a 62-year-old man – paratumorous abscess (case 2). Both cases were characterized by the development of regional and distant metastases (liver, brain) and a short relapse-free period. We found rare sporadic mutations of KRAS A146V and A59G with microsatellite stability and no mutation in the V600 BRAF site.Discussion. In the presented case 1, the KRAS A146V mutation was detected, the frequency of its detection in our practice of testing 2103 cases of CRC was 0.48%. Case 2 shows the extremely rare A59G mutation. Among the patients with CRC we studied, we found mutations in codon 59 in only two, which amounted to 0.095%. Both rare mutations represent separate molecular subgroups of CRC, characterized by an unfavorable clinical outcome and requiring the development of special treatment regimens.