Oncocytic rectal adenocarcinomas

Oncocytic rectal carcinomas are rare and have only been documented sporadically. Oncocytes are encountered in 2 distinct settings: after preoperative chemoradiation (commoner) and without antecedent chemoradiation (uncommon). The aim of this study was to ascertain the incidence and clinicopathologic features of rectal cancers with a significant (>25%) component of oncocytes in cases not receiving chemoradiation. Of 72 cases encountered over the study period, 8 fulfilled the criteria as oncocytes. These tumors, except for the cellular component of oncocytes, were similar to conventional adenocarcinomas pathologically and immunophenotypically. Cells with eosinophilic cytoplasm are commonly seen in rectal adenocarcinomas, and they should be separated from oncocytic examples. True oncocytes may be seen in conventional adenocarcinomas as individual cells or glands, especially at the infiltrating edge of the tumor. All 8 cases appeared to have behaved aggressively with rapid local and/or distant spread over a short duration.