Abstract
Objective: To evaluate the incidence of Microsatellite Instability (MSI) in patients with Colon Cancer in stage II & III in the Mexican population. Methods: This is a descriptive, retrospective and cross-sectional study performed through a review of 30 clinical charts of patients with the diagnosis of Colorectal Cancer and evaluation of Microsatellite Instability in surgical pathology specimens. Results: Males with 53.3% had a higher incidence than females. The most frequent site was the left colon (53%), followed by the right colon (16.6%), higher rectum (10%), mid rectum (10%), and lower rectum (10%). The majority of the patient were classified as moderately differentiated (86.7%), with 6.7% being poorly differentiated and the rest 6.7% well differentiated. For the presence of MSI in repair genes (MLH1, MSH2, PMS2), this was positive in 33% of the population studied. The clinical-stage most frequently affected was IIA with 36.7% of the positive cases followed by stage IIB with 20%, stage IIIA 20%, and finally, stage IIC and IIIB with 13% and 10% respectively. Among histologic subtypes, adenocarcinoma was found in 90% of the cases, mucinous carcinoma in 6.7%, and signet ring cell carcinoma in 3.3%. In regards to treatment, 50 % of patients underwent only surgery while the other 50% were treated with surgery followed by adjuvant chemotherapy. Clean surgical margins were achieved in 93.7% after initial surgery and the rest were taken back to surgery for a wider resection. The predominant tumor size was T2 (50%), T3 (33%), and T4a (16.7%). The most commonly found lymph node involvement was N1a with 63.3% of the cases followed by N1b with 16.7%. In terms of recurrent metastatic disease, M1a was the most frequent, found in 73.3% of the cases. Conclusion: In our study population in contrast with current literature from the rest of the world we found a higher presence of microsatellite instability (33% vs 15%) and a higher incidence in the left colon with a definitive impact in the survival of patients.
Highlights
Colorectal Cancer (CRC) is the third most common malignancy in the western world and the second most common cause of cancer death in North America
In our study population in contrast with current literature from the rest of the world we found a higher presence of microsatellite instability (33% vs 15%) and a higher incidence in the left colon with a definitive impact in the survival of patients
Hospital of México City), with a total of 30 patients included, the results of the presence of Microsatellite Instability (MSI) were significantly higher than those reported in other international studies where the usual incidence oscillates between 10% and 15% at the maximum and has more prevalence in the right colon, in our population the incidence reached up to 33.3% for the presence of MSI with a higher incidence of the left colon which is in contrast with previous reports
Summary
Colorectal Cancer (CRC) is the third most common malignancy in the western world and the second most common cause of cancer death in North America. It presents as a heterogeneous disease at the molecular level. Four Consensus Molecular Subtypes (CMS) in Colorectal Cancer (CRC) were identified in a study by Justin Guinney. The most common presentation is sporadic (85%) or associated with Lynch Syndrome (Hereditary Non-Polyposis Colon Cancer). The MSI-H phenotype is an identity seal of CRC associated with Lynch Syndrome and it is diagnostic of it [4,5,6]
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