Snapshot A 43-year-old man presents to his primary care physican for a pigmented lesion on his right forearm. He has had multiple sunburns in the past and works as a farmer, spending most of the day outside. Physical examination is notable for a 7-mm hyperpigmented lesion that is asymmetric with irregular borders and color variation. He undergoes an excisional biopsy, which demonstrates larger than normal melanocytes of various sizes with large hyperchromatic nuclei in the lower epidermis and dermis. Introduction Overview malignant tumor of melanocytes most commonly affects the skin login to view 5 more bullets 4 types of cutaneous invasive melanoma login to view 8 more bullets Epidemiology Incidence most commonly seen between the ages of 40-60 Risk factors dysplastic nevi multiple nevi ultraviolet radiation exposure fair-skin color immunsuppresion ETIOLOGY Pathophysiology Clark model of pathogenesis melanocytes proliferate to form a benign nevus genetic mutations (e.g., BRAF) lead to the nevus becoming dysplastic (pre-malignant) login to view 2 more bullets Presentation Physical exam pigmented skin lesion ABCDEs login to view 5 more bullets Studies Serum labs S-100 tumor marker Invasive studies excisional biopsy indication login to view 1 more bullet findings login to view 9 more bullets Differential Actinic keratosis differentiating factors secondary to proliferation of atypical epiderminal keratinocytes lesions are small, rough papules that are erythematous or brownish Basal cell carcinoma differentiating factors lesions are waxy, pink, and pearly login to view 1 more bullet histology demonstrates palisading nuclei Treatment Medical vemurafenib indication login to view 2 more bullets Surgical local wide excision indication login to view 1 more bullet Complications Metastatic melanoma lung brain liver bone intestines Prognosis Prognostic favorable favorable localized disease with the tumor being ≤ 1 mm deep negative metastatic disease