Mutational Load Quantification Technique as an Aid to the Histopathologic Evaluation of Barrett's Esophagus
William W Bivin, Jr., Shweta Patel, Jan F Silverman, Brendan Corcoran, Eric Ellsworth, Sara Jackson, Sydney Finkelstein. Allegheny General Hospital, Pittsburgh, PA; RedPath Integrated Pathology, Inc., Pittsburgh, PA
Background: Histopathologic evaluation of dysplasia in Barrett's esophagus (BE) is often challenging with significant interobserver variation. We developed a quantitative mutational load (ML) scoring system as an aid to define disease progression along the spectrum from intestinal metaplasia, through dysplasia to cancer in BE. We hypothesize that ML quantification scoring technique helps recognize mutation count and clonality in stages of disease progression.
Design: We examined formalin-fixed, paraffin-embedded gastroesophageal junction biopsies and esophageal mucosal resections from 22 patients. From these cases, 32 microdissection targets in intestinal metaplasia (IM, n=4), low grade dysplasia (LGD, n=7), high grade dysplasia (HGD, n=13) and carcinoma (CA, n=8) were made and tested for both loss of heterozygosity and microsatellite instability in a panel of 22 microsatellite markers at 10 loci using PCR/capillary electrophoresis. The proportion of cells affected was quantitatively determined, with high clonality mutations representing >75% of cells, and low clonality representing 50-75%. ML was calculated using numbers of low and high clonality mutations and the number of loci affected by microsatellite instability.
Results: All targets in this series showed mutations and a ML increase was present along the sequence of intestinal metaplasia to dysplasia to carcinoma. Microdissected targets with histologic intestinal metaplasia had MLs in the range of 0.50-2.00 (average 0.94). Targets with LGD had mutational loads slightly higher in the range of 1.00-2.50 (average 2.00). The ML between IM and LGD was not significant (p = 0.42). MLs in targets of HGD ranged from 1.50-6.50 (average 3.77), and targets with carcinoma showed the highest ML (average 5.25). The ML between HGD and CA was not significant (p = 0.043). However, the ML between IM/LGD versus HGD/CA was significant (p < 0.0001).
Conclusions: 1.) The technique for evaluating mutational load at individual microdissection targets of BE is quantifiable and can provide useful complementary information for the histopathologic evaluation for dysplasia or malignancy in BE. 2.) ML quantification can be especially helpful in separating LGD from HGD, which can be occasionally challenging in H&E examination.
Tuesday, March 5, 2013 1:45 PM
Proffered Papers: Section E, Tuesday Afternoon