Human papilloma virus (HPV) related oropharyngeal squamous cell carcinoma (OPSCC) has favorable prognosis relative to other head and neck squamous cell carcinomas. Criteria for predicting HPV status based upon p16 staining, including difficult cases with partial staining patterns, have been developed; however, clinical validation of these criteria and the clinical significance of partial p16 staining have not been reported. 81 archival OPSCC cases were initially stained for p16 by immunohistochemistry with clone G175-405. The percentage of p16+ cells and percentage of confluence of p16+ cells were categorized as 25%, 26-75% or >75%. Of all cases, 16 (20%) had partial p16 expression, with 26-75% p16+ cells. Applying previously developed criteria of >75% p16+ cells or >50% positive cells with >25% confluence, 48 (59%) patients were categorized p16+ and demonstrated expected clinical characteristics and superior disease-free survival (DFS) and overall survival (p < 0.001) compared to p16- patients. By themselves, the partial staining patients had intermediate outcomes however, separating the partial staining cases by degree of confluence showed those with >75% confluence had superior DFS (p = 0.042). When the 16 original partial staining cases were re-stained with the alternative anti-p16 E6H4 clone, p16 status remained concordant for all cases, but only 3 of the 16 were interpreted as demonstrating partial staining. This report shows the prevalence of partial p16 staining varies with the antibody utilized and clinically validates the application of a graded evaluation of both the number as well as confluence of positive cells for risk-stratification of patients with OPSCC.
Cancellation of patient tests after a specimen had been collected and received remains a significant issue for clinical laboratories. Laboratories should monitor causes of test cancellation to identify targets for process improvement efforts and to improve laboratory utilization. Cancellation events due to incomplete identification or poor specimen quality potentially delay patient care. Cancellations due to duplicate orders or excessive frequency of testing represent operational challenges for the laboratory and inefficiency in the health care system. Policies related to test cancellation should be clearly specified and communicated to users of laboratory services.
The levels of genomic DNA were significantly decreased in GAA treated vs non-treated TP samples. Aliquoting from the TP sample prior to treatment with GAA enables accurate measurement of DNA without affecting the adequacy of the TP cytology slide.
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