The utility of high-risk human papillomavirus E6/E7 mRNA in situ hybridization in assessing HPV status on cell block

Updates in head and neck cytopathology: Insights from European Congress of Pathology Short Course

Cytological specimens play a pivotal role in head and neck nodule/mass work up and diagnoses. The specimens´ importance has grown with the onset of personalized medicine and the routine use of molecular markers in the diagnostic work up. The Updates in Head and Neck Cytopathology Short Course ran during the 35th European Congress of Pathology held in Dublin, Ireland, in 2023 and brought together experts in cytopathology, pathology, and related fields to share their expertise and experience in the field of head and neck cytopathology and its future directions. Topics such as a one-stop clinic, the Milan System for Reporting Salivary Gland Cytopathology, next generation sequencing, and human papilloma virus detection in the head and neck area were covered during the short course. These topics are briefly summarized in the present review.

Utility of high-risk HPV RNA chromogenic in situ hybridization in cytology smears and liquid-based preparations from metastatic head and neck squamous cell carcinoma

BACKGROUND

High-risk human papillomavirus (HR-HPV) status is critical for the diagnosis, prognosis, and treatment of patients with oropharyngeal squamous cell carcinoma (OPSCC). Patients often present with enlarged cervical nodes, and fine-needle aspiration cytology (FNAC) is frequently the initial diagnostic procedure. Although p16 is the most widely used surrogate marker, problems with interpretation can limit its utility in FNAC. HR-HPV RNA in situ hybridization (ISH) has emerged as a specific way to assess HPV status on cell block preparations of cervical nodes. The authors evaluated the utility of HR-HPV ISH in conventional smears and liquid-based cytology (LBC) preparations of metastatic head and neck squamous cell carcinoma (SCC).

METHODS

Thirty-one aspirates of proven, HPV-related SCC (confirmed by p16 and/or HR-HPV ISH in corresponding surgical specimens) were selected. Ten aspirates of HPV-negative SCC were also retrieved. HR-HPV ISH was performed on 27 smears and 14 LBC preparations. All results were scored as positive, equivocal, or negative.

RESULTS

Eighty-four percent of metastatic, HPV-related SCCs were positive for HR-HPV RNA ISH, with high number of signals (n = 19) and low number of signals (n = 7), whereas five HPV-related SCCs were equivocal. All metastatic, HPV-negative SCCs were negative for HR-HPV ISH.

CONCLUSIONS

HR-HPV ISH can be reliably performed on smears or LBC preparations, particularly when cell blocks are unavailable or paucicellular. Results were easy to interpret when high numbers of signals were present but were challenging in aspirates with low or rare number of signals. The current study suggests that HR-HPV ISH could be used as the initial testing modality for determining HPV status in FNAC specimens of metastatic SCC.

ROC analysis of p16 expression in cell blocks of metastatic head and neck squamous cell carcinoma

BACKGROUND

Oropharyngeal squamous cell carcinoma is associated with human papillomavirus (HPV) and often presents with early metastasis to cervical neck lymph nodes that are amenable to fine-needle aspiration (FNA). The most common method of HPV status determination is p16 immunohistochemistry (IHC). The literature suggests that a lower threshold is needed for p16 positivity on cell block. We examined and quantified p16 IHC staining on cell block and used receiver operating characteristics (ROC) curve analysis to determine an optimal cutoff value with high sensitivity and specificity.

METHODS

Thirty-six FNAs of metastatic squamous cell carcinoma from cervical lymph nodes with p16 IHC were evaluated. The p16 stain was quantified in 5% increments and high-risk HPV mRNA in situ hybridization was performed as a gold standard test. Statistical analysis was performed.

RESULTS

Interobserver variability was evaluated and was shown to be low with an intraclass correlation coefficient of 0.857. ROC analysis was performed and showed that a cell block p16 IHC cutoff of 15% yielded the highest sensitivity (80%) and specificity (81.8%).

CONCLUSION

Our data show that a threshold of 15% p16 staining in cell block maximizes sensitivity and specificity.