BI26: Extramammary Paget disease manifesting in a patient with severe hidradenitis suppurativa

R. Corso,¹ E. Rashidghamat,¹ A. Williams,² N. Watkin,³ E. Calonje¹ and H. Malhomme de la Roche¹

¹St John’s Institute of Dermatology, Guy’s and St Thomas’ NHS Foundation Trust; ²Guy’s and St Thomas’ NHS Foundation Trust; and ³St George’s University Hospitals NHS Foundation Trust, London, UK

Extramammary Paget disease (EMPD) is a rare intraepithelial adenocarcinoma that usually originates in anogenital or axillary skin, which is rich in apocrine glands. We present a case of EMPD diagnosed incidentally in excised skin from a patient who underwent surgical management of extensive hidradenitis suppurativa (HS) of the groin area. A 23-year-old British man of Sri Lankan heritage with Hurley stage III HS was referred from our tertiary HS clinic for surgical management of his groin disease. He had significant extensive perineal, perianal and right axillary disease with indurated plaques and actively discharging sinuses throughout. He had been on adalimumab 40 mg subcutaneously weekly for 16 months prior to his surgery. Previous treatments included oxytetracycline, rifampin and clindamycin, dapsone, isotretinoin and acitretin. Despite satisfactory adalimumab blood levels and negligible antidrug antibody levels, he reported a good initial improvement but then subsequent limited improvement on the medication. He had long-standing iron deficiency anaemia, which had been previously investigated and attributed to his HS. He was otherwise healthy. He underwent examination under anaesthesia, wide excision debridement and laying open of the sinus tracts on both sides of his groin, his perineal area and his natal cleft. Histological examination of the skin excised from the right groin and right scrotum showed glands composed of cells exhibiting both cytological and mitotic atypia. This favoured the diagnosis of primary superficially invasive EMPD with invasion to the excision margins. Following the diagnosis of EMPD, the adalimumab was stopped, and the patient’s HS was managed with co-amoxiclav 500 mg three times daily and amoxicillin 500 mg daily. A malignancy screen was performed to exclude metastatic disease. A computed tomography of the chest, abdomen and pelvis revealed no evidence of metastases and showed a reactive, enlarged right groin lymph node (LN). An oesophagogastroduodenoscopy and colonoscopy were unremarkable. The patient was discussed at the Specialist Skin Multidisciplinary Team meeting and referred to a tertiary urology centre for further surgical management of the EMPD. He underwent definitive excision of the affected area, followed by right-sided inguinal LN dissection. The excised LNs were clear and he is currently undergoing clinical surveillance, with a low threshold to biopsy remaining areas of disease. To our knowledge this is the first reported case of EMPD diagnosed in a patient with comorbid HS. Furthermore, the diagnosis was incidental as the affected area had not appeared to be clinically suspicious for EMPD preoperatively.