DNA Genotyping As a Quality Assurance Measure in Surgical Pathology

Abstract

A 65-year-old man was referred to our institution for excision of an invasive well-differentiated squamous cell carcinoma in his left posterior ear groove that had been diagnosed at a referring institution; however, review of his accompanying pathology slides revealed benign squamous hyperplasia. A repeat biopsy of the site and a biopsy of an adjacent ulcer were submitted to pathology along with a revised clinical impression of basal cell carcinoma (BCC). Both biopsies showed squamous hyperplasia and degenerative mesenchymal alterations. In addition, one of the slides contained a tissue fragment with chatter artifact and BCC. A pickup was suspected since the remaining tissue fragments were devoid of BCC. DNA identity testing using short tandem repeat (STR) analysis was performed to determine whether or not the BCC belonged to the patient. Different allelic patterns (14/16 STR markers) between the fragment and other patient tissue samples confirmed that the fragment was a pickup, belonging to another patient, and presumably introduced at the gross bench. This case illustrates the importance of STR analysis as quality assurance in the anatomic pathology laboratory.