Colon adenoma and adenocarcinoma with clear cell components - two case reports

Abstract

Background Diagnoses reflect clear cell morphologies when tumor cells have clear cytoplasm in many organs, and the nature of such clear cells is typically identified. Colorectal tubular adenoma or adenocarcinoma, conversely, rarely show clear cells, the reason for which remains uncertain. We report 2 colon tumors with clear cell components (Case 1: adenoma; Case 2: adenocarcinoma) and investigate the nature of the clear cells. Case presentation Case 1 was a 75-year-old man with a superficial elevated polyp detected in the rectum for whom endoscopic submucosal dissection was performed. Microscopically, 10% of the tumor showed dysplastic columnar epithelium with clear cytoplasm forming tubular structures accompanied by conventional tubular adenoma. Case 2 was a 58-year-old man with a pedunculated polyp found in his sigmoid colon for which polypectomy was performed. Microscopically, 90% of the tumor showed dysplastic columnar epithelium with clear cytoplasm forming fused glands or cribriform structures adjacent to the ordinal tubular adenocarcinoma. In both cases, clear and ordinary tumor cells were negative for CK7 and positive for CK20 and CDX2, consistent with findings of colorectal origin. Different results were found for CEA and CD10 staining. CEA was positive on the luminal side of the conventional area in contrast diffuse cytoplasmic staining of the clear cell area in both cases. CD10 was only positive for the clear cell component of case 2. The clear cell components were negative for Periodic acid-Schiff (PAS), Alcian blue, and mucicarmine staining and AFP immunohistochemistry. An ultrastructural examination found multiple cytoplasmic lipid-like vacuoles in the clear cell component that were predominantly negative for adipophilin by immunoelectron microscopy. Conclusions We investigated tubular adenoma and tubular adenocarcinoma with clear cell components. The accompanying conventional tubular adenoma or adenocarcinoma cells helped us to evaluate the atypia of the clear cells. Diffuse cytoplasmic staining of CEA and CD10 suggested that the clear cell component might harbor malignant potential. We were unable to verify the well-known causes of clear cytoplasm, such as an accumulation of glycogen, lipid, or mucin and enteroblastic differentiation. The causes of clear cells in the colorectal region remain uncertain; however, possible explanations include autolysis and carbohydrate elution.

Incidental morphological findings in colorectal adenomas

“…The clear cells show an immunohistochemical pattern similar to that of the adenoma component. They usually show expression of CK20, carcinoembryonic antigen, and CDX2, consistent with the finding of a colorectal origin, and are negative for CK7, vimentin, and chromogranin 35–39 …”

“…Clear cells have no accumulation of mucin, and show no expression of Alcian blue or Periodic acid-Schiff (PAS), either before or after diastase digestion, [37][38][39][40] in contrast to the conventional adenomatous component. 36,40 The clear cells show an immunohistochemical pattern similar to that of the adenoma component. They usually show expression of CK20, carcinoembryonic antigen, and CDX2, consistent with the finding of a colorectal origin, and are negative for CK7, vimentin, and chromogranin.…”

“…The incidence of clear cell metaplasia in colorectal adenomas is very low; in a large series of 3486 cases, it was 0.086% 34 . It has been suggested that these adenomas are more often observed in the distal colon and rectum, 35,36 although this could not be confirmed in other studies 3,37,38 . The adenomas are not particularly large, and they are found predominantly in middle‐aged men, at an average age of 54 years 3,36–38 …”

“…Clear cells have no accumulation of mucin, and show no expression of Alcian blue or Periodic acid–Schiff (PAS), either before or after diastase digestion, 37–40 in contrast to the conventional adenomatous component 36,40 . The clear cells show an immunohistochemical pattern similar to that of the adenoma component.…”

“…3,37,38 The adenomas are not particularly large, and they are found predominantly in middleaged men, at an average age of 54 years. 3,[36][37][38]…”