Desmoplastic malignant melanoma and its variants. A study of 45 cases.

Forty-five tumors exhibiting the histological features of desmoplastic malignant melanoma or its variant, neurotropic melanoma, were found among approximately 4,500 soft-tissue tumors referred in consultation from Australia and New Zealand. All patients were Caucasians. Tumors fell into three groups: (a) desmoplastic melanoma with an atypical intra-epidermal melanocytic component (classical desmoplastic melanoma) (12 cases); (b) desmoplastic melanoma without an atypical intra-epidermal melanocytic component (de novo desmoplastic melanoma) (21 cases); (c) predominantly nerve-centered superficial malignant tumors with or without an atypical intra-epidermal melanocytic component (12 cases). Three of the nerve-centered tumors were associated with pigmentary abnormalities in the overlying skin. The patients' ages ranged from 42 to 91 years, with a peak in the seventh decade; 31 patients were male and 14 were female. Lesions were located in the head and neck (35 cases), shoulder and arm (four), back and chest (three), abdomen (one), thigh (one), and leg (one). Three tumors arose in irradiated areas, and one occurred on the face of a radiotherapist. Melanin was found in only four tumors, but the S-100 protein stain was positive in 19 tumors and negative in three. Follow-up details of 42 patients were available. In follow-up times from 4 months to 15 years (mean, 4.6 years), 15 patients (36%) had died of the disease or were terminally ill; 24 (57%) were alive with no apparent residual tumor; and three (7%) had died of other causes. Twenty-three patients (55%) developed one or more local recurrences; 17 (40%) developed distant spread, including extension into the cranial cavity along nerves; and 14 (33%) had both local recurrence and distal spread. Nine (82%) of 11 patients with nerve-centered tumors died or were terminally ill. The usual treatment was surgical. Most uncontrolled recurrences were resistant to chemotherapy and radiotherapy; however, two patients responded well, one to chemotherapy and one to radiotherapy. Our observation support Reed and Leonard's metaplastic explanation for the varied differentiation seen in desmoplastic melanomas.