Signet-ring cells associated with pseudomembranous colitis

Abstract

Sir,Signet-ring cells (SRCs) are most commonly associated with mucus-producing malignant epithelial tumors. They may also be found in thyroid lesions, nonepithelial neoplasm, and, in reactive conditions, in a variety of sites [2,4]. Here we report the clinical, microscopic, and immunohistochemical features of two cases of pseudomembranous colitis showing benign SRCs.Case 1 was a 49-year-old man was admitted to hospital due to bacterial meningitis treated with antibiotic therapy including cefotaxim and tobramycin. On the 5th day in hospital the patient developed severe abdominal pain and abdominal distension. At laparotomy features of toxic megacolon were found, and a partial left colon resection with colostomy was performed. Twelve months later he underwent another operation to reconstruct the intestinal transit, and in the postoperative period he had fecaloid peritonitis due to suture dehiscence as well as bleeding in the digestive tract due to subcardial ulcer, which were surgically treated. Currently, 3 years after he was first operated on, the patient is alive with a defect in the abdominal wall due to the repeated surgery.Case 2 was a 69-year-old man with a history of partial right colon resection for well-differentiated adenocarcinoma without mucinous component. After surgery the patient developed abdominal pain, tenderness, distension, and fever and was treated with mefoxitin, amikacin, and clindamycin. Since the symptoms became more severe, on the 13th day after surgery he underwent resection of the remaining part of right colon and transverse colon. Another synchronous well differentiated adenocarcinoma without mucinous component was found in transverse colon. There is no follow-up.Macroscopically, we found dilatation of the colon in both cases, the thickness of the wall was increased, and the mucosal surface displayed multiple yellow patches of exudate (Fig. 1). Furthermore, an anular (constrictive) mass of 3 cm diameter was found in case 2. Histologically the two specimens showed similar findings, with transmural acute inflammation and formation of pseudomembranes (Fig. 2a). Focally the crypt epithelia appeared distended and replaced by signet-ring shaped cells (Fig. 2), which were mucicarmine positive (Fig. 3a). Occasional SRCs were also seen in the pseudomembranes. The signet cells showed peripherally placed nuclei and intracytoplasmic vacuoles. The nuclei were not enlarged, displayed uniform chromatin distribution, and had either no nucleoli or mitotic figures. SRCs were not present in the lamina propria outside the crypts. Immunohistochemically the SRCs were positive for cytokeratins (20, clone CAM5.2, and clone AE1-AE3; Fig. 3b) and E-cadherin (Fig. 3c) while uniformly negative for CD68 (KP1), MIB-1, bcl-2, and p53.The current SRC formation in pseudomembranous colitis has been reported only in four previous cases [1,3,4,5]. As occurred in our patients, toxic megacolon developed after antibiotic therapy, showing a gross and microscopic picture of pseudomembranous colitis. The recognition of benign ...

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