Lymph node metastases in malignant colonic polyp with favourable histology detected by PET CT.

Case Report A 49-year-old man presented with malaise and shortness of breath for 1 month. Physical examination showed pallor. His blood picture showed hypochromic, microcytic anaemia with haemoglobin of 8.3 gm/dl. Colonoscopy [Olympus, Tokyo, Japan] showed a 3.0 cm large pedunculated polyp at 35 cm from the anal verge in the descending colon. An Endoloop [Olympus, Tokyo, Japan] was placed at the base of the polyp with an Endoloop Applicator [Olympus, Tokyo, Japan]. En bloc resection of the polyp was performed with SensationTM Polypectomy Snare [Boston Scientific, Nanterre, France]. Histology of the polyp showed a completely removed tubulovillous adenoma with severe dysplasia (Fig. 1). Focal transformation into well differentiated adenocarcinoma (Fig. 2) was observed at the head of the polyp. Areas of submucosal invasion were limited to the head of the polyp. The stalk of the polyp was identified and a clear resection margin of 3.2 mm was achieved. The pericolic lymph nodes showed moderately increased 18 Fluorodeoxyglucose (18FDG) activity with a maximum Standard Uptake Value (SUVmax) of 5.6 on PET CT scan. The largest pericolic lymph node was 0.5 cm in size. The descending colon showed mild uptake with SUVmax 2.8, which can be related to post-procedural changes. His carcinoembryonic antigen was normal. The CT of the thorax, abdomen and pelvis were normal. He underwent a repeat colonoscopy with tattooing of the polypectomy site followed by a laparoscopic left hemicolectomy. On histology, the previous polypectomy site showed early regenerative changes with no evidence of residual dysplasia or malignancy. The resection margins were clear. Two of the 9 pericolic lymph nodes sampled had evidence of metastatic adenocarcinoma without capsular involvement (Fig. 3).