Metastatic squamous cell carcinoma in a patient treated with adalimumab for hidradenitis suppurativa

HPV: human papilloma virus HS: hidradenitis suppurativa MU: Marjolin ulcer TNF-a: tumor necrosis factor-a INTRODUCTION Hidradenitis suppurativa (HS) is a chronic, debilitating, inflammatory skin condition characterized by recurrent painful nodules, cysts, and abscesses that can rupture and lead to the formation of sinus tracts and scarring. In 2015, the tumor necrosis factor-a (TNF-a) inhibitor, adalimumab, was approved for the treatment of moderate-to-severe HS. TNF-a inhibitors may increase the risk of nonmelanoma skin cancers, particularly squamous cell carcinoma (SCC). Patients with HS are 4.6 times more likely to go on to have nonmelanoma skin cancer than the general population. Although the reasons for the increased risk in HS are not entirely understood, a known complication of scarring and chronic inflammation is a Marjolin ulcer (MU), a malignant degeneration (most commonly SCC) occurring in up to 3.2% of patients with HS. Here we report a case of metastatic SCC, believed to be a MU, that developed in an HS patient being treated with adalimumab.