The prognostic significance of tumor necrosis in colorectal cancer is unclear. Our study aimed to analyze the prognostic value of tumor necrosis with respect to progression-free and cancer-specific survival and to relate findings to expression of proteins involved in the control of cancer cell death, such as p53 and bcl-2. A total of 381 colorectal cancer specimens were retrospectively reevaluated. The extent of tumor necrosis was semiquantitatively assessed and recorded as either absent, focal (≤10% of the tumor area), moderate (10%-30%), or extensive (≥30%). Expression of p53 and bcl-2 was assessed immunohistochemically and recorded as either positive (using a cutoff value of 10%) or negative. In addition, mismatch repair protein status was assessed by immunohistochemistry using antibodies directed against hMLH1, hMSH2, and hMSH6. Tumor necrosis was observed in 365 (96%) cases, with 180 (47%) tumors showing focal necrosis, 119 (31%) moderate necrosis, and 66 (17%) extensive necrosis, respectively. Extent of necrosis was significantly associated with high T classification (P < .001), high N classification (P = .005), high International Union Against Cancer stage (P < .001), poor tumor differentiation (P < .001), large tumor size (P < .001), and blood vessel invasion (P = .01). No association of tumor necrosis with expression of p53, bcl-2, and mismatch repair protein status was observed. Tumor necrosis proved to be an independent prognostic variable with respect to progression-free and cancer-specific survival. In conclusion, tumor necrosis showed significant impact on prognosis of colorectal cancer patients. Its presence is readily assessable in hematoxylin and eosin-stained sections and should therefore routinely be commented upon in the pathology report.
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