Desmoid tumour in an inguinal hernia in a patient with a previous diagnosis of melanoma

A 68-year-old man, without a family history of cancer, was treated for primary cutaneous melanoma of the scalp. Two years later, a right lateral cervical lymph recurrence was observed and he was treated with lymphadenectomy and adjuvant nivolumab for 1 year. Four years from the initial melanoma diagnosis, a computer tomography scan showed a solid nodular lesion of 26 × 40 × 75 mm inside the previously known inguinoscrotal hernia. A new recurrence of melanoma was the most probable diagnosis and a right inguinal hernioplasty was performed. Notably, the histopathological examination revealed a mesenteric fibromatosis with the typical immunohistochemical pattern (strong nuclear staining of β-catenin). Interestingly, this represents the first case of a patient with a mesenteric desmoid tumour presenting as an inguinal hernia masking a cutaneous melanoma recurrence.