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Comparative Study
. 2019 Dec;127(12):750-756.
doi: 10.1002/cncy.22191. Epub 2019 Oct 10.

Cytologic evaluation of p16 staining in head and neck squamous cell carcinoma in CytoLyt versus formalin-fixed material

Darren J Buonocore  1 , Evan Fowle  1   2 , Oscar Lin  1 , Bin Xu  1 , Nora Katabi  1 , Jean-Marc Cohen  1
Affiliations
Comparative Study

Cytologic evaluation of p16 staining in head and neck squamous cell carcinoma in CytoLyt versus formalin-fixed material

Darren J Buonocore et al. Cancer Cytopathol. 2019 Dec.

Abstract

Background: The management of high-risk human papillomavirus (HR-HPV)-related oropharyngeal head and neck squamous cell carcinomas (HNSCCs) are distinct from HNSCC linked to smoking and alcohol use. HR-HPV-positive HNSCC frequently presents as a cervical lymph node metastasis. Because fine-needle aspiration (FNA) is often the initial diagnostic procedure, evaluating HR-HPV status in cytology specimens is important. The overexpression of p16 is a surrogate for HR-HPV; however, the evaluation of p16 in FNAs remains controversial.

Methods: From September 2015 to December 2016, cytopathologists performed 25 FNAs of neck lymph nodes that were suspicious for HR-HPV-positive HNSCC. Initial passes produced smears for on-site evaluation and CytoLyt material. Additional passes were formalin-fixed. A CytoLyt cell block (CCB) and a formalin-fixed cell block (FFCB) were prepared, and p16 immunocytochemistry was performed.

Results: In 24 of 25 cases, the FFCB had diffuse (≥70% of cells), strong nuclear/cytoplasmic p16 staining. In all 24 of these cases, HR-HPV was detected by in situ hybridization. The corresponding CCB had weak-to-moderate p16 staining in <70% of cells (range, 5%-60% of cells) in 17 cases, 4 had weak-to-moderate diffuse staining, and 4 were acellular. The percentage of p16-positive cells was significantly higher with FFCB than with CCB (formalin: 94% ± 2%; CytoLyt, 38% ± 7%; 2-tailed, paired Student t test; P < .001; Fisher exact test, P < .001).

Conclusions: The fixative used had a drastic impact on p16 staining, which explained the staining variability reported in the literature. FFCBs show a diffuse staining pattern, which correlates with HR-HPV status, whereas CCBs show a weaker and inconsistent staining pattern, which is more difficult to interpret.

Keywords: cytology; human papillomavirus (HPV); p16; squamous carcinoma.

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Conflict of interest statement

Disclosure of conflict of interest: The authors declare no conflict of interest

Figures

Figure 1:
Figure 1:
A) H&E of squamous cell carcinoma. B) Diffuse p16 staining on FFCB
Figure 2:
Figure 2:
A) H&E of squamous cell carcinoma. B) Diffuse p16 staining on FFCB. C) Positive for HR-HPV by in situ hybridization
Figure 3:
Figure 3:
Three representative cases of squamous cell carcinoma (A,D,G) with side by side comparison of p16 staining on the CCB (B,E,H) and the FFCB (C,F,I) respectively
Figure 4:
Figure 4:
Comparison of p16 staining in tumor cells in CytoLyt® and Formalin
See this image and copyright information in PMC

References

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