The distinction between serrated polyps of the colon is complex, particularly between hyperplastic polyps (HP) and sessile serrated adenomas (SSA). Recent data show that SSA might be the precursors of serrated colonic cancers, underlining the necessity of identifying them. We characterized the demographic and pathologic characteristics of 102 serrated lesions among 321 polyps of the colorectum and determined if SSA can be microscopically distinguished from HP in biopsy material of a daily practice. There were 81 HP (79%) and 7 SSA (7%) of which one displayed lowgrade dysplasia. Only six serrated polyps (6%) could not be correctly classified. The main architectural criteria for distinguishing SSA from HP is the serrated feature along the crypt axis and the rarity of undifferentiated cells in the lower third of the crypts. SSA was significantly more often located in the right colon and larger (median, 11 vs 4 mm) than HP. SSA are rare serrated polyps that can be distinguished from HP based on their morphology, location in the right colon, and larger size. One SSA of our series showed low-grade dysplasia supporting the concept that this lesion might be a precursor of serrated adenocarcinoma.

HPs and SSAs may be related lesions. However, at least right-sided SSAs differ from left-sided SSAs and HPs in the occurrence of MLH1 and p16 methylation, supporting the hypothesis that SSAs could be precursors of serrated adenocarcinomas.

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Colonic malakoplakia can occur either as a part of systemic disease with multiple colonic and extracolonic deposits or as an incidental finding associated with a rectal or sigmoidal adenocarcinoma.A case is reported which shows an association between malakoplakia and adenocarcinoma of the caecum.

Collagenous and lymphocytic colitis might be part of the same disease spectrum. In this report, we present a histopathologic subtype of microscopic colitis characterized by the presence of subepithelial multinucleated giant cells. This reaction is very unusual and not explicable by any underlying disease process or previous treatment. Among 490 cases of microscopic colitis (MC) diagnosed between 1992 and 2002, we found 2 cases with macrophages and giant cells (0.4%). One case of lymphocytic colitis (LC) and 1 case of collagenous colitis (CC) presented aggregates of macrophages and giant cells located in the superficial part of the lamina propria. Infectious or non-infectious colonic granulomatous diseases were excluded on histologic, clinical, and biological grounds. The recognition of this feature in an MC is important to avoid the diagnosis of granulomatous infectious or idiopathic colitis such as Crohn's disease. Even if very unusual, this subtype of MC evolves favorably since the 2 patients responded well to corticosteroid treatment.

Colorectal cancer with microsatellite instability (MSI) may occur sporadically or be inherited in cases of hereditary nonpolyposis colorectal cancer (HNPCC) syndrome. However, there is no consensus as to which patients must be tested and how to test MSI. In this study, MSI was tested by immunohistochemical analysis and by polymerase chain reaction in 148 cases of colorectal cancer, and methylation of the hMLH1 promoter was examined. MSI status was correlated with tumor phenotype. We found that localization, tumor infiltrating lymphocytes, and mucinous differentiation were predictive of high-frequency MSI (MSI-H) colorectal cancer and might be used to select cases for MSI analysis. Immunohistochemical analysis detected most MSI-H colorectal cancer and might constitute the first step in MSI detection. Absence of hMLH1 promoter methylation in MSI-H colorectal cancer could be predictive of hereditary colorectal cancer, and, hence, methylation analysis might constitute the second step in the identification of patients with HNPCC.

Irinotecan (CPT-11) is a chemotherapeutic drug used to treat tumors by acting on malignant cells through inhibition of DNA topoisomerase I and inducing premature apoptosis. Major toxic effects of Irinotecan are myelosuppression and gastrointestinal (GI) toxicity, which limits the dose of administration, particularly severe diarrhea with a delay of onset. However, according to the literature, serious GI side effects are uncommon, comprising 3% of the reported cases. The mechanism of Irinotecan-induced delayed diarrhea is unknown and unpredictable. To our knowledge, this is the first case of colitis associated with Irinotecan administration for temporal glioblastoma documented by biopsies. The histopathologic findings are described and the potential mechanisms inducing such lesions are discussed.

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