Abstract Background: The medical literature reports on the diagnostic challenges posed by tissue contamination and transposition among surgical biopsy specimens. These specimen provenance complications (SPCs) can lead to a misdiagnosis of cancer, resulting in unnecessary surgery and a potential delayed diagnosis. The histopathology process involves many manual steps during which specimens must be estranged from their identification, and provenance errors are often invisible absent DNA analysis. Prostate biopsy is the setting in which specimen provenance has been studied, with complication rates reported in over 0.9% of positive diagnoses despite best efforts to minimize errors. Because the processing workflow is virtually identical for histopathology specimens of all types, it is expected that error rates among breast biopsy specimens are similar to prostate. Methods: We analyzed over 4200 patients diagnosed with breast cancer between February 2011 and April 2014. All biopsies were collected using a uniform best-practice protocol including forensic chain of custody principles, bar-coding of specimen containers, and collection of the patient’s reference DNA sample via buccal swab. After a pathologic diagnosis of breast cancer a portion of the diagnostic specimen was forwarded to an independent DNA laboratory (Strand Diagnostics, Indianapolis, IN) where genetic STR profiles were compared to the patient’s reference DNA to rule out the presence of undetected SPCs prior to therapy. Results: 3545 breast cancer cases from 7 practices contributing 100 or more cases each were examined (Fig1). DNA testing revealed occult provenance complications in 15 cases (.42%), of which 6 (.17%) were a complete transposition with another patient and 9 (.25%) reflected contamination of the specimen by tissue from one or more unidentified individuals. Three (43%) of the practices experienced at least one provenance error during the study period, with the highest error rate being 1.41% at one practice. Pathology was performed by 14 different laboratories, 6 (43%) of which were implicated in occult SPCs (Fig2). Finally, patients seen by 7(11%) of the 62 physicians performing surgical biopsies in the cohort were subjects of occult specimen provenance errors. Conclusions: These data suggest that the incidence of SPCs among breast biopsies is comparable to that reported for prostate biopsies. The errors are distributed broadly across laboratories, practices, and physicians. Due to the potential clinical consequences for patients with undetected SPCs, and the medical malpractice implications, further study of the nature and economics of provenance complications in the breast biopsy setting is warranted. Fig 1 Type IType II PracticeCasesErrorsErrorsSPC Rate (%)A220548.54B617 0C173 0D162 1.62E1422 0F128 0G118 0Total354569.42Figure 1 SPCs by Practice Type I=Transpositions Type II=Contanimations Fig 2 Type IType II LabCaseErrorsErrorsSPC Rate (%)A143523.35B967 3.31C430 0D2602 .77E182 0F84 11.19G78 0H712 2.82I20 0J9 222.22K5 0L2 0M1 0N1 0Total354569.42Figure 2 SPC's by Path Lab Type I=Transpositions Type II=Contaminations Citation Format: Arthur G Lerner, Arla L Bush, Andrew S Kenler, David D Dorfman, Travis A Morgan, Beth Boyd, William E Burak, Richard E Fine. Incidence of misattributed specimen provenance among surgical breast biopsies [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-02-08.