In colorectal cancer, KRAS (exons 2, 3, and 4) and NRAS (exons 2, 3, and 4) mutations are associated with resistance to antiepidermal growth factor receptor monoclonal antibodies, and BRAF mutation is a molecular marker of poor prognosis. KRAS exon 2 and BRAF-mutated colorectal cancers have well-known distinct clinicopathological characteristics. Comparison of tumors with different RAS status (exons 2, 3, and 4 of KRAS and NRAS) based on their clinicopathological characteristics has never been established. All colorectal cancer patients with RAS and BRAF testing from 2011 to 2015 were included in this observational retrospective study. Patient and tumor characteristics were collected and correlation with RAS and BRAF status was evaluated. A total of 1735 patients with colorectal cancer were included. RAS-mutated colorectal cancers (n=1002), compared with RAS wild-type colorectal cancers (n=733), were significantly associated with male gender, classical adenocarcinoma subtype, well/moderately differentiated tumors, and microsatellite stable phenotype. KRAS codon 13-mutated colorectal cancers (n=171), compared with RAS wild-type colorectal cancers, more frequently presented classical adenocarcinoma subtype and microsatellite stable phenotype. In comparison with other RAS mutations, KRAS exon 3-mutated colorectal cancers (n=23) were associated with mucinous/rare histological subtypes and, most likely to located in the rectum. KRAS exon 4-mutated colorectal cancers (n=33) were more frequently associated with mucinous/rare histological subtypes. There was no significant association between NRAS mutation (n=37) and clinicopathological features. Colorectal cancers are associated with different clinicopathological features according to the type of RAS mutation. Consequently, these particular characteristics must be considered when assessing the prognostic value of RAS status in colorectal cancer.

Aims: Basal cell carcinoma (BCC) is a common cancer, with a high risk of local recurrence. A quantifiable measurement of the histological margins of BCC in excisions is a recurrent demand of clinicians; however, there are currently no international guidelines indicating its value. Methods and results: A questionnaire validated by four experts in dermatopathology and formatted under a 'Google Forms'-type interface was sent by e-mail to physicians specializing in surgical pathology or dermatopathology and practising in France from 20 March 2018 to 20 May 2018. The results were compared between subgroups according to age and subspecialisation, especially dermatopathology. The questionnaire was completed by 225 practitioners. Microscopic margins were systematically measured in 77.3% of cases, sometimes in 19.6% and never in 3.1%. The main reason was to report factually insufficient margins (66.5%), followed by laboratory routine (45%) or clinician requests (43.1%). For 72% of respondents, the clinical or histopathological criteria did not influence their practice. The most used tool was a graduated ruler placed under a microscope (44.3% of cases). Compared to other groups, dermatopathologists measured BCC margins less systematically [only in certain situations (33.3 versus 14.9%) or never (10.5 versus 0.6%) (P < 0.001)] and used an eyepiece reticle more extensively (53.1 versus 29.8%; P = 0.0029). Conclusion:The measurement of histological margins in BCC is common practice in France, although there are no recommendations. Our survey suggests that it represents a way for pathologists to specify an insufficient margin and therefore the need for scar revision.