Clear cell adenocarcinoma: a rare variant of primary colonic tumour

Colonic de novo Clear Cell Adenocarcinoma of Intestinal-Type: A Case Report and Review of the Literature

Colorectal clear cell adenocarcinomas are rare tumors. They can be divided into two types: intestinal- and Müllerian-type. Most intestinal-type clear cell adenocarcinomas show a composite morphology, and most early-stage (T1) intestinal-type clear cell adenocarcinomas have an adenoma component. We report an additional early-stage (T1) colonic clear cell adenocarcinoma that was a de novo adenocarcinoma without any adenoma component. It had a pure morphology and the smallest size (0.6 cm) ever reported. Immunohistochemical results demonstrated an intestinal phenotype (KRT20+, KRT7-, CEA+, and CDX2+). Periodic acid-schiff and alcian blue stains were both negative, which demonstrated decrease in mucin expression in the clear tumor cells. Enteroblastic differentiation was observed in a few colorectal clear cell adenocarcinomas in the literature, while it had not been observed in the present tumor. The tumor did not have deep submucosal invasion and cancer embolus, endoscopic submucosal dissection with regular follow-up was an appropriate treatment for the patient. Due to the rarity and diversity of primary colorectal clear cell adenocarcinomas, the cause of clear cytoplasm change and the impact on patient prognosis remain unknown. Accumulating evidence indicates that clear cell adenocarcinomas of intestinal-type is a histological variant of colorectal adenocarcinoma.

Mucinous Adenocarcinoma of the Colon with Clear Cell Component: A Case Report and Literature Review

Clear cell adenocarcinomas of the colon are defined as a subtype of colorectal adenocarcinoma with clear cell morphology. A 65-year old man was admitted to a Gastroenterology Department for diagnostic evaluation of a tumor in the sigmoid colon found on CT. There, the patient developed complete bowel obstruction and was operated urgently, where intraoperatively, a large tumor in the sigmoid fixated to the lateral abdominal wall was revealed. A subtotal colectomy was performed. Histopathological analysis of the surgical specimen was conducted. The immunohistochemistry staining was positive for CEA, CDX2, and CD20 and negative for CK7, CD10, MUC2, AFP, and PAS staining. Mismatch repair protein testing was negative. The pathological diagnosis was mucinous carcinoma with a clear cell component which bears an extremely low incidence that has been scarcely reported in literature. This stresses the need for more case reports like ours to be published.

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

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.