The immune cell infiltrate in the microenvironment of vulvar Paget disease

Non-invasive vulvar Paget disease (VPD) is a rare skin disorder mainly affecting elderly women. Recently, the immune modulator imiquimod was reported as an effective treatment option. Knowledge about the immune microenvironment of VPD is lacking.

This study investigates the basic characteristics of the immune infiltrate in VPD (n = 10); moreover the influence of imiquimod was studied (n = 6). Immunohistochemistry for CD4, CD8, CD14, CD20, CD56 and FoxP3 was performed. The infiltrates of VPD were compared to vulvar high-grade squamous cell intraepithelial lesions (HSIL) (n = 43), a HPV induced vulvar premalignancy with known response to imiquimod cream, and healthy controls (n = 30). Immune cell counts in samples taken before and after treatment were compared.

The microenvironment in VPD differs from the healthy vulvar skin and vulvar HSIL. VPD is characterized by a decrease in immune cells in the epithelium and an abundant number of immune cells in the stroma, consisting predominantly of T cells. The intraepithelial CD8+/Foxp3+ ratio and number of CD56+ increased after imiquimod therapy, whereas the numbers of CD14+ cells decreased which may point to a treatment-induced type 1 immune response.

The epithelium in VPD contains less immune cells, but a dense stromal immune infiltrate. Changes in immune cell counts after immune modulation in relation to clinical responses should be further investigated.