Cancer and hidradenitis suppurativa.

Patients with hidradenitis suppurativa (HS) have an increased risk of developing cancer. This includes not only hematologic malignancies and solid tumors but also cutaneous squamous cell carcinoma (SCC) originating within the HS lesions. The development of SCC is most commonly associated with Caucasian men who smoke and have severe gluteal or perianal lesions of more than 25 years. Other factors that have occasionally been associated with HS-related SCC include treatment with a tumor necrosis factor-alpha inhibitor (such as infliximab and adalimumab), genodermatoses (such as keratitis-ichthyosis-deafness syndrome and Dowling-Degos disease), and paraneoplastic syndromes (such as hypercalcemia, hypercalcemia-leukocytosis, and paraneoplastic neuropathy). The tumor may demonstrate the presence of human papillomavirus; even after treatment, patients have a poor prognosis because cancer metastasis, recurrence, or both commonly occur. The potential role of human papillomavirus vaccination for cancer prevention and early treatment of SCC with targeted therapy (with an epidermal growth factor inhibitor such as cetuximab) and/or checkpoint inhibitor immunotherapy (such as cemiplimab and pembrolizumab) remains to be determined. Rarely, HS lesions have mimicked cutaneous metastases in patients with visceral malignancy by demonstrating an increased uptake of fluorine-18 fluorodeoxyglucose on positron emission tomography and/or computed tomography scans. Primary cancers (such as cutaneous SCC and mucinous adenocarcinoma) and breast cancer skin metastases can masquerade as HS lesions. When a lesion is located at a current or earlier site of HS that is new or rapidly growing and/or does not respond to HS-directed therapy, prompt evaluation to establish or exclude the diagnosis of cancer should be considered.