Cutaneous melanoacanthomas manifest as pigmented papules, plaques, cutaneous horns or nodules. Melanoacanthomas have been described more frequently in white patients. They develop in the middle-aged and the elderly like any other type of seborrheic keratosis. They are found mainly on the trunk or head, often on the lip or eyelid. Melanoacanthoma, a benign mixed tumor of melanocytes and keratinocytes,[3
] although rare, may clinically mimic pigmented seborrheic keratosis and malignant melanoma.[7
] However characteristic histopathological features will differentiate the above three lesions. Two histologic types of melanoacanthomas are described: a diffuse type in which melanocytes are unevenly scattered throughout the lesion and a clonal type in which melanocytes and keratinocytes are clustered in small nests. There was partial or complete disturbance of transfer of melanin from these highly dendritic melanocytes to neighboring keratinocytes. Immunofluorescent studies and an immunoprecipitin assay have shown that melanoacanthomas are not related to malignant melanoma, and hence, removal by simple excision, curettage or cryotherapy should be curative.[10
In our case, presence of large number of melanocytes even deep into the tumor mass instead of restricting to the basal layer  has excluded pigmented seborrheic keratosis[8
] from the diagnosis. Huge size, marked tenderness, preliminary presence of pigmented patch from childhood at the site of the lesion also led us to think a provisional diagnosis of melanoma in the present case. Dermoscopic features  did not support the diagnosis of malignant melanoma Cribriform pattern of ridges, characteristic of seborrhoeic keratosis was noticed. This confirms the current view that melanoacanthoma represents a variant of seborrheic keratosis rather than a distinct entity.[2
Histopathological features  depicting no evidence of cellular atypia or pagetoid upward extension of tumor cells, however, did not also speak in favor of malignant melanoma.
The only Indian case report[10
] had shown multiple lesions of maximum diameter 6 cm on the lower abdomen, inner thighs, external genitals, and perianal areas for the past 10 years. Our case, as compared, was giant measuring of maximum diameter 10 cm × 5 cm, solitary, and site was lower back.
We were prompted to publish this case report for: 1) giant size of melanoacanthoma, which has not much been reported in the earlier literature; 2) clinical dilemma with malignant melanoma; 3) importance of dermoscopy and histopathologcal examination in the exclusion of malignant melanoma from melanoacanthoma.