Probes for P16

Current human papillomavirus (HPV) detection methods in oropharyngeal squamous cell carcinoma (OPSCC) have varying sensitivity and specificity. We aimed to compare different HPV-detection methods against the test used in clinical practice, ie, p16 immunohistochemistry (IHC) and to evaluate whether another HPV-detection test additional to p16 IHC would be worthwhile in OPSCC specimens. The study cohort comprised 357 consecutive OPSCC patients during two time periods: 2000-2009 and 2012-2016. From tumor tissue slides, HPV mRNA via in situ hybridization (ISH), HPV DNA via ISH and HPV DNA via polymerase chain reaction (PCR) were detected. The results of these methods were compared with p16 IHC results. Additionally, clinicopathological factors were compared with the methods studied. The sensitivity of HPV mRNA ISH, HPV DNA ISH and HPV DNA PCR were 93.4%, 86.3%, and 83.5%, respectively. The corresponding specificity was 92.4%, 95.3%, and 89.1%, respectively. The negative predictive value for p16 IHC was highest (89.0%) when using mRNA ISH, and followed by DNA ISH (83.5%). ISH for high-risk HPV E6/E7 mRNA was found to be a highly specific and sensitive method for detecting HPV in OPSCC. As p16 protein may be overexpressed due to HPV-independent mechanisms, all p16 IHC-positive OPSCCs should be considered for retesting using mRNA ISH in order to verify transcriptionally active HPV. This is especially critical when considering de-escalated treatment approaches for patients with HPV-positive tumors and still maintaining favorable outcomes for this subgroup of patients

Abstract

BACKGROUND:

Human papillomavirus (HPV)-related squamous cell carcinoma (SqCC) of the oropharynx is an epidemiologically and clinically distinct form of SqCC that is associated with an improved prognosis. However, HPV-related small cell carcinoma of the oropharynx is a rare and newly described variant that is associated with aggressive clinical behavior and poor outcomes. To date, fewer than 2 dozen reports of this entity exist in the literature, and there is no discussion of cytopathologic features. This article reports 6 cases and discusses the salient cytomorphologic findings, ancillary studies, and challenges when this entity is encountered.

METHODS:

Anatomic pathology archives were searched to identify patients with a diagnosis of HPV-related small cell carcinoma of the oropharynx. Medical records were reviewed to document the following: age, sex, smoking status, other relevant clinical history, primary location, treatment, and clinical outcome. Both p16 and high-risk HPV in situ hybridization (ISH) studies were positive in at least 1 specimen from each patient. The pathologic diagnoses, cytomorphologic characteristics, immunocytochemical stains, and HPV ISH studies were reviewed and recorded for all available cases.

RESULTS:

Six patients with 11 cytopathology specimens of HPV-related small cell carcinoma of the oropharynx were identified. The mean age was 61.3 years, and all patients died with widely metastatic disease (mean, 23 months; range, 12-48 months). Mixed small cell carcinoma and SqCC components were present in half of the cases.

CONCLUSIONS:

The identification of a small cell component can be reliably performed with cytology preparations and is crucial because this (and not the HPV status) determines the prognosis.