What are tumors of fibrous tissue?

Tumors of fibrous tissue are mesenchymal tumors composed of fibroblasts or their variants. Fibroblasts produce normal structural components of the dermis, including collagen, elastin, and ground substance (dermal mucin). Most tumors of fibroblast origin produce collagen, but they may also produce dermal mucin or elastin as the primary product. Some tumors are composed primarily of myofibroblasts, specialized fibroblasts that demonstrate contractile properties because of cytoplasmic actin filaments. Other specialized fibroblasts may demonstrate phagocytosis, and tumors demonstrating this characteristic are referred to as fibrohistiocytic tumors. Tumors of fibrous tissue are conventionally divided into those that are fibrous and those that are fibrohistiocytic (Table 43-1).


 

Table 43-1. Fibrous Tumors of the Skin
	BENIGN FIBROUS TUMORS		MALIGNANT FIBROUS TUMORS		BENIGN FIBROHISTIOCYTIC TUMORS*		MALIGNANT FIBROHISTIOCYTIC TUMORS
	Acquired digital fibrokeratoma Acrochordons Connective tissue nevus (collagenoma, elastoma) Dermatomyofibroma Desmoids (extra-abdominal and abdominal fibromatosis) Fibrous hamartoma of infancy Infantile digital fibromatosis Knuckle pads Nodular fasciitis Keloid		Fibrosarcoma		Fibrous papule Dermatofibroma Reticulohistiocytoma (solitary or multiple) Xanthogranuloma (including juvenile xanthogranuloma) Giant cell tumor of tendon sheath		Atypical fibroxanthoma Dermatofibrosarcoma protuberans Malignant fibrous histiocytoma
	*Some dermatologists consider atypical fibroxanthoma to be a benign fibrohistiocytic tumor, but this is controversial.