Clinicopathological Characteristics With the Status of Mismatch Repair Deficient Invasive Colorectal Cancer With Spontaneous Regression.

Spontaneous regression of endoscopically invasive colorectal cancer (CRC) after biopsy has been rarely reported. We report three cases of endoscopically invasive CRC with spontaneous regression after biopsy and a review of the literature regarding spontaneous regression of CRC with somatic mismatch repair deficiency (MMR-d). Case 1 involved a 54-year-old man who underwent a colonoscopy (CS) after positive fecal immunohistochemical test. A 15-mm elevated lesion with a depression was detected in the transverse colon, and biopsy results indicated adenocarcinoma. When surgical resection was performed 8 weeks later, the lesion was no longer present. Case 2 involved a 75-year-old man with a 10-mm elevated lesion with a depression in the ascending colon during screening CS. Biopsy results indicated adenocarcinoma. CS was performed 9 weeks later to tattoo the lesion before surgery; however, it was no longer present at that time. Case 3 involved an 84-year-old man who underwent surveillance CS after polyp resection and a 12-mm elevated lesion with a depression was observed in the rectum. Biopsy results indicated adenocarcinoma; therefore, endoscopic resection was scheduled. CS performed 8 weeks later showed the disappearance of the lesion. Mismatch repair deficiency was detected in two of these three patients. The literature search identified 12 cases with the evaluation of MMR, including our three cases, which showed spontaneously regressing colorectal cancer. All 12 lesions had depression; 11 were located on the proximal colon, and 11 cases showed MMR-d.