Presentation
Abdominal pain and constipation.
Patient Data
There are two foci of focal colonic wall thickening with stricture identified at the distal transverse colon/splenic flexure and rectosigmoid transition. No bowel obstruction. No signs of metastatic disease.
Increased FDG uptake within the colonic lesions is in keeping with colorectal tumors. No metastatic disease.
Arrows pointing to the synchronous colorectal tumors on both CT and PET modalities.
Macroscopy: A. Labeled "Left hemicolectomy and anterior resection". A segment of large bowel 580 x 40 mm with attached mesentery 90 mm. Two separate lesions are identified. The 1st is located 52 mm from the closest longitudinal margin (designated margin 1). It is an ulcerated tumor 25 mm in length and 30 mm in diameter, present on the antimesenteric surface. The tumor extends through the muscularis propria to abut the serosal surface where it is is associated with a smooth area of pallor 20 x 10 mm (serosal surface inked green). In this area, a small amount of the subserosal fat 8 x 4 mm is present on the antimesenteric aspect into which the tumor directly extends. The tumor is 30 mm from the closest non-peritonealised mesenteric margin. An area of dark grey discolouration, 25 x 15 mm is present adjacent to the tumor, toward margin 1, in keeping with a tattoo.
The 2nd tumor is located 55 mm from margin 2 (415 mm from tumor 1) and is a near circumferential, stenosing tumor 20 mm in length. In this area the bowel lumen is narrowed to 7 mm. The tumor extends through the muscularis propria to abut the serosal surface where it is associated with an area of puckering and adherent fat 15 x 10 mm (inked black). The tumor extends through the muscularis propria into this adherent fat, total depth 13 mm. It is present 28 mm from the closest non-peritonealised mesenteric resection margin.
The bowel between tumor 1 and tumor 2 has a luminal diameter of 50 mm and is associated with thinning of the bowel wall to 1 mm.
Microscopy: A. Tumor 1 is a moderately differentiated adenocarcinoma comprising irregular glandular structures lined by markedly atypical columnar epithelial cells, infiltrating within a desmoplastic stroma. In areas, there is abundant extracellular mucin (<50% of the tumor). The carcinoma invades into subserosa (A3). No serosal invasion is seen. Lymphovascular space invasion is identified but no extramural venous invasion is seen.
Tumor 2 is a moderately differentiated adenocarcinoma comprising irregular, sometimes cribriform glandular structures lined by markedly atypical columnar epithelial cells, infiltrating within a desmoplastic stroma. Carcinoma invades through the full thickness of the colonic wall and extends to the serosal surface. No definite vascular invasion is seen.
Ten of twenty-five (10/25) mesenteric lymph nodes show metastatic adenocarcinoma including nodes adjacent to both tumors. The apical node is also involved.
Elsewhere, a small hyperplastic polyp is present toward margin 1. The colon at the resection margins is otherwise within normal limits. The colon between the two tumors show mild mural thinning.
Opinion: Left hemicolectomy and anterior resection: Two separate foci of moderately differentiated adenocarcinoma.
Case Discussion
This patient underwent surgery (left hemicolectomy) with diagnosis confirmation of synchronous adenocarcinoma NOS pT4a, N2b.
Synchronous colorectal cancers are characterized by the presence of others distinct tumoral foci at diagnosis, intra-operatively, or within 6 months of the resection of the primary lesion. After the 6 months, a new distinct colorectal cancer is called metachronous 1.
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