Home Books Fitzpatrick's Dermatology in General Medicine, 8e

Chapter 66. Dermal Hypertrophies and Benign Fibroblastic/Myofibroblastic Tumors

Christine J. Ko

Dermal Hypertrophies and Benign Fibroblastic/Myofibroblastic Tumors at a Glance

Common benign dermal fibrous lesions include hypertrophic scar, keloid, dermatofibroma, and acrochordon.
Certain benign tumors with a prominent dermal connective tissue component (e.g., angiofibroma, fibrofolliculoma/trichodiscoma, acrochordon-like lesions, and connective tissue nevi) may be associated with genetic disorders.
Some dermal hypertrophies and tumors (e.g., desmoid tumor, infantile fibromatosis, infantile myofibromatosis) can at times be aggressive with high rates of recurrence.
Other entities that present in infancy and childhood include fibrous hamartoma of infancy, fibromatosis colli, infantile digital fibromatosis, calcifying aponeurotic fibroma, juvenile hyaline fibromatosis, and infantile systemic hyalinosis.
Other entities that primarily affect adults include adult fibromatoses (palmoplantar, penile, knuckle pads), pachydermodactyly, reactive lesions (nodular fasciitis, elastofibroma), solitary lesions (acquired digital fibrokeratoma, dermatomyofibroma, pleomorphic fibroma, collagenous fibroma, myofibroma, solitary fibrous tumor), and clinically distinctive hypertrophies (cutis verticis gyrata, pachydermoperiostitis, cerebriform fibrous proliferation).

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.

Table 66-1 Fibroblastic/Myofibroblastic Tumors of Infancy and Childhood

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Table 66-1 Fibroblastic/Myofibroblastic Tumors of Infancy and Childhood

Skin Involvement

Entity

Typical Site(s)

Often solitary

Infantile digital fibromatosis

Myofibroma

Calcifying aponeurotic fibroma

Plantar fibromatosis

Infantile fibromatosis

Fibrous hamartoma of infancy

Fibromatosis colli

Cranial fasciitis

Digits

Head/neck

Palms/soles

Soles

None

Upper arm/trunk

Clavicle area

Head/neck

Often multiple

Juvenile hyaline fibromatosis

Ears/face and other sites

Often multiple with visceral involvement

Infantile systemic hyalinosis

Infantile myofibromatosis

Ears/face and other sites

None

Table 66-2 Differences between Fibroblasts, Myofibroblasts, and Smooth Muscle Cells

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Table 66-2 Differences between Fibroblasts, Myofibroblasts, and Smooth Muscle Cells

Fibroblast

Myofibroblast

Smooth Muscle Cell

Nucleus

Tapered

Tapered to cigar-shaped

Cigar-shaped

Positive immunohistochemical stains

Vimentin

CD34 (sometimes)

Vimentin

Smooth muscle actin

Muscle specific actin

Vimentin

Smooth muscle actin

Muscle specific actin

Desmin

Negative immunohistochemical stains

Smooth muscle actin

Muscle specific actin

Desmin

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, ...