Case report
A 52-year-old man with a 6-year history of UC (left-sided colitis) was admitted to our hospital because of umbilical pain and low-grade fever. Oral administration of 5-aminosalicylic acid had been discontinued one year earlier due to clinical remission. A colonoscopy performed one year earlier showed an endoscopic remission. At this time, a mild inflammation was observed around the appendix orifice. He had no family history of malignancies.
Physical examination on admission showed tenderness in the right lower quadrant of the abdomen, but there was no peritoneal irritation sign. Laboratory examination revealed an elevation of C-reactive protein (2.01mg/dl), but tumor markers such as carcinoembryonic antigen and carbohydrate antigen 19-9 were within normal range. A contrast material-enhanced computed tomography scan showed a stenotic change of the proximal ascending colon by a mass showing extramural growth (Figure1A). The extramural part of the mass extended to the dilated appendix with intraluminal tumor growth (Figure1B). A colonoscopy on admission showed a circumferential stenosis of the proximal ascending colon and the lumen was spread by air supply, suggesting extramural compression. (Figure 2). The mucosa surface was reddish but intraluminal growth of the tumor was not observed. Pathological examination of biopsy specimens showed no malignancy.
A laparoscope-assisted right hemicolectomy was performed on the 9th day after admission. Macroscopically, the appendix was dilated and strongly adhered to the proximal portion of the ascending colon (Stage IIIB [T4b, N1a, M0] according to the TNM classification). Pathological examination revealed a primary adenocarcinoma mixed with an adenoma component of the appendix (Figure 3). The tumor invaded the serosal side of the proximal ascending colon. Dysplasia was not identified in any pathologically examined specimens. Genomic analysis of carcinoma cells revealed the KRAS G13D mutation. His postoperative course was uneventful, and adjuvant chemotherapy was started from 6 weeks after surgery.