Skin toxicity due to telaprevir: a new drug we should be familiar with.

Ultrastructural studies and immunophenotyping have shown these cells to be fibroblasts and myofibroblasts. The immunohistochemical profile is very variable, although vimentin is frequently expressed. CD34 expression has been reported in some cases; this can complicate the diagnosis as dermatofibrosarcoma protuberans must then be considered in the differential diagnosis. Immunohistochemistry is useful to orient the pathologist, but the diagnosis is fundamentally morphological. Treatment is surgical, and recurrence is rare after excision with an adequate margin. Tardío et al. gathered a total of 34 cases in children and 56% of those tumors were found on the neck, as in the 2 patients we describe. A primary characteristic of pediatric dermatomyofibroma therefore appears to be its tendency to arise in the cervical region. In adults, on the other hand, the tumor arises most frequently on the shoulders or proximal region of the limbs and is less common on the neck. The second characteristic is that the tumor predominantly affects boys. In adults, 90% of cases are in women. It has been speculated that the tumor may spontaneously regress in male children at puberty and persist in girls, leading to a higher prevalence in adult women. The importance of this disease is its differentiation from other tumors formed of spindle cells, such as desmoid tumor and dermatofibrosarcoma protuberans. In addition, other mesenchymal lesions more typical of the pediatric age range, such as fibrous hamartoma of infancy, myofibromatosis, connective tissue nevus, and smooth muscle hamartoma, must be excluded. A guide to the differential diagnosis of these tumors is presented in Table 1.