Dermatofibroma: causes, symptoms, diagnosis, treatment

Dermatofibroma (syn.: histiocytoma, angiofibroxanthoma, sclerosing hemangioma, fibroxanthoma, nodular and subepidermal fibrosis) is a benign tumor of connective tissue in the form of a slowly growing painless node, a single, less often multiple nodular or plaque-like formation with a diameter of about 1 cm, slightly elevated in the center.

The causes and pathogenesis of dermatofibroma are not understood.

Symptoms of dermatofibroma. In most cases, the disease occurs in women. A round tumor-like formation appears, deeply embedded in the skin. The tumor is a single or multiple mobile node. The tumor is small (from 2-3 mm to 1.0-1.5 cm), has a dense consistency and a dark brown color and protrudes in the form of a hemisphere above the skin surface. Also, the tumor can be, as if soldered, drawn into the skin so that its upper pole is at the same level with the skin surface. Subjective sensations are absent.

Palpation is dense, easily mixed, the surface is smooth, sometimes hyperkeratotic, warty. The color is usually reddish-brown, more saturated in old elements. It occurs more often in young women, mainly on the lower extremities. Multiple disseminated small dermatofibromas can be combined with osteopoikilosis (Buschke-Ollendorff syndrome)

Histopathology. Histologically, clusters of mature and young collagen fibers arranged in different directions, fibroblasts, histiocytes and an abundance of small blood capillaries with edematous endothelium are noted. Multinucleated Touton cells are rare.

Pathomorphology. The large number of synonyms of dermatofibroma indicates significant variability of the histological picture. In this regard, some authors distinguish dermatofibroma variants into separate nosological units. This primarily concerns such variants as angiofibroxanthoma and histiocytoma. In our opinion, it is appropriate to consider these tumors as varieties of dermatofibroma, since their morphological features, as well as histogenesis, are similar. They differ only in the predominance of one or another component and the degree of their maturity.

The constituent elements of any variant of dermatofibroma are fibroblastic cells, fibrous substances and vessels. Depending on the predominance of the constituent component, fibrous and cellular types of tumor can be distinguished.

The fibrous type is characterized by the predominance of mature and young collagen fibers, located in different directions, in places in the form of twisted bundles and moire structures. Areas of young collagen are stained with hematoxylin and eosin in a pale blue color, the fibers are located separately, and not in the form of bundles. The cells are predominantly mature (fibrocytes), but there may also be young forms - fibroblasts. The tumor is sometimes sharply demarcated from the surrounding dermis, sometimes its borders are blurred.

The cellular type of dermatofibroma is characterized by the presence of a large number of cellular elements, mainly fibroblasts, surrounded by a small number of collagen fibers. Among the fibroblasts, histiocytes are located, sometimes in the form of nests. They are larger than fibroblasts, their nuclei are oval, the cytoplasm contains a significant amount of lipids and hemosiderin. In some tumors, histiocytes predominate, among which are located (sometimes in large numbers) Touton cells. These are large cells with numerous nuclei, sometimes grouped, in a massive cytoplasm. The peripheral parts of the cytoplasm of these cells contain birefringent lipids, sometimes typical xanthomatous cells can be seen. In some cases, the latter predominate, located in the form of nests among the fibroblastic elements, in connection with which this variant of dermatofibroma is called fibroxanthoma. The stroma of the fibroma cell type consists of delicate, loosely arranged collagen fibers, in places with the presence of rhythmic structures.

In all variants of dermatofibromas, vessels of various calibers with swollen endotheliocytes are found. In some cases, capillary vessels are found in large quantities among the cellular elements and fibrous structures, which gives some authors grounds to call such a tumor a sclerosing hemangioma. Sometimes, along with capillary-type vessels, larger vessels with sharply widened lumens are observed, having the appearance of cracks, located in connective tissue, where collagen fibers form characteristic moire structures. Birefringent lipids are found in fibroblastic elements (angiofibroxanthoma according to the classification of L.K. Apatenko).

Histogenesis. All the above-described histological varieties of dermatofibroma have a single histogenesis. It is noted that the fibroblastic elements of the tumor have a potential for phagocytosis, so they often contain lipids and iron. Scientists have identified acid phosphatase activity in fibroblasts of all types of dermatofibroma. This is also confirmed by electron microscopy data. Thus, SG Carrington and R.K. Winkelmann (1972), studying dermatofibroma with a large amount of lipids and hemosiderin, showed that phagocytic cells have all the features of fibroblasts: oval nuclei, expanded endoplasmic reticulum and perinuclear arrangement of fibrillar structures.

Differential diagnosis. Dermatofibroma should be differentiated from lipoma and pigmented nevus.

Treatment of dermatofibroma. Surgical (electroexcision) excision of the tumor is performed. Corticosteroids can be injected into the lesion.

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