[Spontaneous numbness along with pre-existing deviations in the pigmentation of the lower lip].

A 48-year-old man was referred for an evaluation of deviations in the pigmentation of the lower lip, intra-oral swelling and persistent numbness of the sensory area of the left mental nerve. In 2011, the diagnosis lentigo maligna of the lower lip was missed by histopathology of a biopsy performed elsewhere. In 2016, the numbness of the lower lip and chin was diagnosed by a neurologist as numb chin of unknown cause. A biopsy in 2017 showed lentigo maligna of the lower lip alongside a primary mucosal melanoma with significant local invasion. Treatment consisted of a hemimandibulectomy with a supraomohyoid neck dissection of the left side. This case shows the importance of the alarm symptom 'a numb lip' and the corresponding necessity of additional investigation. This article shows avoidable pitfalls that general practitioners, dentists and medical specialists need to be vigilant about.