Chapter 66. Dermal Hypertrophies and Benign Fibroblastic/Myofibroblastic Tumors

Dermal hypertrophies and benign fibrous tumors are quite common. Some of the entities described have characteristic clinical presentations and histopathologic features. Many primarily present in infancy and childhood (Table 66-1). A unifying histologic feature of hypertrophic scars and most of the rarer entities described is the presence of myofibroblasts, contractile spindle cells that express smooth muscle actin but not desmin (Table 66-2). Malignant fibrous tumors of the dermis are discussed in Chapter 125.

Keloids and hypertrophic scars are related clinical lesions.1 These lesions present at sites of prior dermal injury and wound repair. They often occur after local skin trauma (e.g. laceration, tattoo, burn, injection, ear piercing, vaccination, or surgery) or inflammatory skin disorders (e.g. acne, bites, or infections). There may be growth of keloids during pregnancy.2 The predisposition to keloids in darker skin3 and reports of a familial, autosomal dominant inheritance4 suggest genetic influences. Hypertrophic scars and keloids show differences morphologically and histologically (Table 66-3),5,6 suggesting differences in pathogenesis. There also is an apparent association with melanin pigment, ...