Background:Most patients with oral mucosal melanoma have had a mucosal hyper pigmented area for months or even years before the diagnosis, it is important to consider the differential diagnosis of mucosalmelanoma, which in many cases is a difficult diagnosis and because of the aggressive biological behavior of mucosal melanoma it is important to do a quick diagnosis.Main observation:A 40-year-old Mexican male patient, presented with a lesion on the lower right half of the lip covering almost the entire vermillion border, 1 mm below the white roll. The lesion was a 1.5 x 4 cm pigmented macule with asymmetric and irregular borders and colors. Dermoscopy showed a multi component pattern. An incision biopsy was performed under the impression of mucosal melanoma. The pathologic report described a Clark I vermillion edge mucosal melanoma in situ. Conclusions:This case had confounding clinical signs that could have misguided the clinician. But dermoscopy proved to be useful when suspecting a malignant lesion, which prompted a biopsy and a correct diagnosis.