The authors present five cases of an unusual inflammatory reaction in pelvic peritoneal tissues associated with oxidized regenerated cellulose, a topical hemostatic agent. The findings were observed in specimens from five women who had been treated with oxidized regenerated cellulose during abdominal surgery. Histologically, the lesion was characterized by collections of large cells beneath the mesothelial surface, with small bland nuclei and abundant granular basophilic cytoplasm that stained bright red with mucicarmine. Immunohistochemical studies demonstrated that these cells stained positive for KP1 (CD68) confirming their histiocytic nature, and negative for cytokeratin and S-100 protein excluding the diagnoses of carcinoma and granular cell tumor respectively. Although unlikely, the mucicarmine positivity may be misinterpreted, leading to a erroneous diagnosis of adenocarcinoma. To avoid misdiagnosis, pathologists need to be aware of this lesion.