Tissue Prior to the Initial Hematoxylin-Eosin Section Demonstrates Value as an Alternative Source of DNA for Molecular Testing

Context.—: Small biopsies are used for histologic, immunophenotypic, cytogenetic, molecular genetic, and other ancillary studies. Occasionally, this diagnostic tissue is exhausted before molecular testing can be performed.

Objective.—: To investigate a simple banking protocol for currently discarded tissues trimmed off prior to the initial hematoxylin-eosin section, as an alternative source of DNA for molecular studies.

Design.—: Mock biopsies of lung adenocarcinomas, benign testes, and B-cell lymphomas were constructed from biobank blocks; these simulated biopsies were assessed via epidermal growth factor receptor (EGFR) p.L858R droplet digital polymerase chain reaction (PCR), Biomed B-cell clonality testing by PCR, or a custom next-generation sequencing panel for lymphomas. For each cancer mock biopsy, DNA amounts and molecular test results from the "trimmings" samples were compared to data from corresponding molecular samples acquired via a "standard" clinical protocol.

Results.—: The data show that although trimmings samples usually contained less DNA than standard samples, both sample classes generally had sufficient DNA for testing and produced essentially identical molecular results. A single sample showed low-level carryover contamination on droplet digital PCR testing.

Conclusions.—: Tissue trimmings banked by using the studied protocol demonstrated value as a potential alternative sample for molecular testing.