Clear cell adenocarcinoma: a rare variant of primary colonic tumour

Dear Editor: Since the first report of primary clear cell adenocarcinoma of the large intestine published in 1964, only seven cases have been reported in literature. In this paper, we describe the eighth case of this rare oncological entity. Immunohistochemical study is indispensable in establishing the primary colonic origin of the lesion. A previously healthy 84-year-old woman was admitted in our hospital because of ferriprive anaemia, necessitating a blood transfusion. Her past medical history included high blood pressure, arthritis and appendicectomy. On admission, the patient presented no complaint. On physical examination, the patient was found to be completely oriented, with no abnormal signs. Colonoscopy revealed an ulcerated, stenotic and infiltrated tumour developed in the left colon at 40 cm from anal margin. Biopsy specimen of the tumour showed an adenocarcinoma. Abdominal echography and computed tomographic scan found no metastatic extension and no abnormal findings from liver, kidneys, genital tractus and ovaries. A left segmental resection was performed with an end-to-end anastomosis. No complementary treatment was performed. The patient was discharged in good health and free of disease 9 months after surgery. Gross examination of the surgical specimen revealed a 30 cm length of colon. An ulcerated tumour involved the mucosa and infiltrated through the full thickness of the colonic wall. It measured 3.5×1.5 cm. Twenty-one lymph nodes were found. Histology of the tumour showed an ulcerated surface. The tumour was entirely composed of cells with microvacuoled cytoplasm and a centrally located nucleus. However, most of the tumour had a pronounced glandular pattern, cribriform areas were also identified. There was moderate nuclear pleomorphism, and numerous foci of necrosis were observed. The adjacent colonic mucosa was devoid of dysplasic features. Histochemical examination of the cytoplasm of the clear cells showed no periodic acid-Schiff (PAS) and alcian blue pH 2.5 staining. Red oil staining failed to detect lipid, and ultra structural examination found no glycogen and no lipid. Immunohistochemical staining showed diffuse strong positive membrane staining of tumour cells with CEA (ZYMED, San Francisco, USA). There were also diffuse cytoplasmic strong positivity for cytokeratin 20 (Dakocytomation, Trappes, France), but no staining for cytokeratin 7 (Dakocytomation), CD 10 (Novocastra, Newcastle Upon Tine, UK) and vimentin (Dakocytomation). Overexpression of p53 (Dakocytomation) was not observed. Ki-67 MIB-1 (Dakocytomation) labeling index was calculated by counting the positive nuclei per 1,000 cells; 44% of tumoural cells show a positive staining. Apoptotic index was calculated by counting positive tumoural cells staining with anti-activated caspase-3 (BD Biosciences, Franklin Lakes, USA) per 1,000 cells; 10% of tumoural cells showed a positive staining. Expression of MLH1, MSH2 and MSH6 (Diagnostic BioSystems, Pleasanton, USA) was preserved. Upon the bases of these findings, the diagnostic of primary clear cell adenocarcinoma of the colon was made. The tumour infiltrated through the full thickness of the colonic wall into surrounding fat and serosa. All lymph nodes were regular. Tumour stage was T4b N0 M0. Primary clear cell colonic adenocarcinoma is a very rare entity, with only seven cases described in the Englishlanguage literature. Most reported patients are men, and all Int J Colorectal Dis (2008) 23:137–138 DOI 10.1007/s00384-007-0291-1