Lichenoid, erosive and ulcerated dermatofibromas. Three additional clinico-pathologic variants.

On the occasion of a case of dermatofibroma with histological lichenoid features, we reviewed from our files all the cases in which the epidermis, usually hyperplastic in dermatofibroma, was, in some way, partially or completely destroyed. Among a total of 484 dermatofibromas, we found three lichenoid, six erosive and two ulcerated cases. In the three lichenoid cases, the columnar epidermal basal cells were lacking (squamotization of the basal layer) and in two of them there was a cleft between the epidermis and the dermatofibroma. Three of the six eroded cases were large pedunculated dermatofibromas with inflammatory phenomena of variable intensity. One case was in the center of a plaque of lichen simplex chronicus with some eroded area. In the other two cases, as well as in the two ulcerated lesions, neither inflammation nor epidermal changes usually attributed to rubbing or scratching were seen. Only in three of the eleven cases dermatofibroma was proposed (with question mark) as a clinical diagnosis. Both follow-up and histopathology supported the benign nature of these cases. We may conclude that: i) Lichenoid, erosive and ulcerated changes in dermatofibroma are infrequent phenomena which may make a clinical diagnosis difficult; and ii) in the presence of an otherwise histopathologically typical dermatofibroma, erosion and ulceration should not be considered as suspicious of malignancy.