The primary peritoneal cancer is a low prevalence disease, within which primary papillary serous carcinoma of the peritoneum is the most frequent with an incidence of 6.78 cases per million inhabitants. Predominates in females and its main differential diagnosis is advanced ovarian papillary serous carcinoma, for which immunohistochemistry and clinical and pathological classifications are the way to differentiate base on the World Health Organization classification for tumor lesions. Objective: Describe the immunohistochemical results of a series of cases studied in Universidad de Chile Clinical Hospital and to compare them with the literature. Material and Methods: Descriptive retrospective study based on analysis of biopsies from 12 cases between January 2010 and March 2015 classifying them according to age, sex and biopsy register. Routine histological technique was performed in addition to the immunohistochemical staining for WT1, cytokeratin and other reagents according to the differential diagnoses. Results: The age distribution was 47 to 75 years, mean 60 years, 100% of cases female. Immunohistochemical reagents were predominant WT1 (53.8%) and cytokeratin-7 (38.5%). Conclusion: This carcinoma is a rare entity in routine clinical practice, with similarities to ovarian serous carcinoma. There is consensus on the diagnosis of this condition, which must be oriented according to the criteria of the Gynecologic Oncology Group. Clinical suspicion can lead the pathologist to perform immunohistochemical study and thus have an accurate diagnosis to determine the therapeutic approach of the surgeon.
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