Dermal melanocytosis can occur in a range of conditions.
Reactive:
(1) frictional dermal melanosis (lifa disease)
(2) stasis dermatitis
Benign melanocytic lesions:
(1) nevus of Ota
(2) nevus of Ito
(3) compound and intradermal nevi
(4) blue nevus
(5) dermal melanocyte hamartoma
(6) mongolian spot (congenital dermal melanocytosis)
(7) pigmented desmoplastic trichilemmoma
(8) hypohidrotic ectodermal dysplasia
(9) constitutional mismatch repair deficiency
(10) acquired dermal melanocytosis
(11) GM1-gangliosidosis
Malignant tumors:
(1) malignant melanoma
(2) diffuse cutaneous melanosis in metastatic melanoma
(3) malignant blue nevus
(4) pigmented squamous cell or basal cell carcinoma
Differential diagnosis:
(1) drug-induced hyperpigmentation
(2) melasma
(3) tattoo
(4) occupational "tattoo"
