Contiguous verrucous proliferations in syringocystadenoma papilliferum: A retrospective analysis with additional evaluation via mutation-specific BRAFV600E immunohistochemistry.

Background: Syringocystadenoma papilliferum (SCAP) is an uncommon cutaneous adnexal proliferation. There have been several reports describing collision lesions of SCAP and verruca, although little is known about the frequency of this association. Molecular testing has revealed the BRAFV600E mutation in a large proportion of SCAP cases, although its expression pattern has not been previously evaluated.

Methods: In this retrospective analysis, we explored the potential histopathological association between verruca and SCAP. We also evaluated mutation-specific BRAFV600E expression in these lesions by immunohistochemistry. Cases of SCAP diagnosed over a 7-year period were closely reviewed for the presence of contiguous verrucous proliferations. Additional sections were cut and stained using the BRAFV600E-specific clone VE1 antibody.

Results: Contiguous verrucous proliferations were identified in 9 out of 12 identified cases. Furthermore, expression of the BRAFV600E mutation was identified in 7 out of 12 cases. Interestingly, in SCAP associated with endophytic verrucous proliferations (n = 4), expression of BRAFV600E was found in both the glandular and the contiguous hyperplastic squamous epithelium.

Conclusion: Overall, these findings suggest that contiguous verrucous proliferations in SCAP are common. Both components of the neoplasm may express the BRAFV600E mutation, which is suggestive of a common origin.