[2013] Malignant Colonic Polyps: Diagnostic Accuracy and Quality of Surgical Pathology Reports

Erica L Schollenberg, Weei-Yuarn Huang, Heidi L Sapp. Queen Elizabeth II Health Centre & Dalhousie University, Halifax, NS, Canada

Background: The goal of population-based colon cancer screening programs, such as the one recently launched in our province, is to diagnose and treat more neoplastic lesions at a pre-invasive or early invasive stage. Pathologists can therefore expect to encounter more so-called “malignant polyps,” defined as adenomatous polyps in which malignant glands invade into submucosa. The appropriate management of these patients depends on the accuracy and completeness of the surgical pathology report. The goal of the present study was to review a set of potentially problematic malignant polyps in order to determine 1) the completeness and accuracy of the original reports, and 2) the incidence and characteristics of false-positive reports.
Design: Diagnoses of non-rectal colonic adenocarcinoma initially made on endoscopic mucosal biopsies were collected, representing 762 cases over a period of 11 years. 564 biopsies (74%) were followed up by colectomy in our institution. Of these, 32 cases (6% of 564) of biopsy-diagnosed invasive carcinoma were followed up with no evidence of malignancy on resection specimens. The biopsy slides for these cases were reviewed by two gastrointestinal pathologists, who classified each case as either malignant (true invasion) or benign (pseudo-invasion).
Results: Of the reviewed biopsies, 24 (75%) were deemed to represent true malignant polyps. The original reports on half of these (12 cases) were incomplete. Of the remaining 8 problematic cases, 6 were biopsies from the left colon. 3 cases were reclassified on retrospective review as false positive diagnoses (representing 0.5% of the 564 patients who underwent colectomy). In 5 cases, the two reviewing pathologists were unable to reach a consensus diagnosis on the presence or absence of invasion.
Conclusions: In this series, most diagnoses of malignant polyps were accurate, although a significant number of reports lacked complete information necessary to guide management. The diagnosis of early invasion in this context can be challenging, and surgical pathologists need to be aware of the diagnostic pitfalls. There is a need to develop ancillary tests for resolving diagnostic dilemmas.
Category: Quality Assurance

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 295, Tuesday Morning


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