[Tumor-infiltrating lymphocytes can be used to screen for lynch syndrome - a case report].

Lynch syndrome is an inherited syndrome associated with the development of colorectal and various other cancers. A 65- year-old male underwent a laparoscopic-assisted right hemi-colectomy for ascending colon cancer (cStage II). Histologically, his tumor was diagnosed as a poorly differentiated adenocarcinoma. Lymphocytic reactions, such as tumor-infiltrating lymphocytes (TIL), and Crohn's-like reactions, were observed. Genetic testing revealed the presence of a pathogenic mutation in the MLH1. In the Lynch syndrome, the most frequently observed findings include the accumulation of mutations, and an early onset of familial colon cancer. Although the case presented here did not show the typical clinical findings of Lynch syndrome, histological examination of the lymphocytic reactions proved useful for screening for Lynch syndrome. Herein, we establish the important role of the pathologist in alerting the clinician to the possibility of Lynch syndrome when the findings of TIL and Crohn's-like reactions are detected.