Dermatomyofibroma (plaque-like dermal fibromatosis)

Are You Confident of the Diagnosis?

Dermatomyofibroma is a rare, benign, cutaneous neoplasm. Typically it presents as an indurated, plaque-like lesion on the shoulder girdle. Often the lesion will have been present for some time with slow growth. The prototypical patient is a young to middle-aged female; however, there have have been case reports of males and children with these lesions.

Characteristic findings on physical examination

On physical examination, a dermatomyofibroma most often presents as an indurated, firm dermal plaque or nodule with or without overlying epidermal hyperpigmentation. Often these lesions are more easily palpated than seen. Dermatomyofibroma are usually seen on the upper trunk, upper arm, axilla, or neck, and are typically small with a normal size of 1 to 2cm. Larger lesions have been reported.

Expected results of diagnostic studies

Because of its rarity, dermatomyofibroma usually requires biopsy for diagnostic confirmation. Histologically, dermatomyofibroma consists of a spindle cell proliferation that is arranged in well-defined, intersecting fascicles (Figure 1, hemoatoxylin and eosin). These spindle cells are often described as slender, and will arrange parallel to the epidermis. An important differentiating factor for dermatomyofibroma is the presence of normal to increased levels of elastic fibers, which are sometimes fragmented. This is in contrast to the reduced elastic fibers typically seen in dermatofibroma, hypertrophic scar, dermatofibrosarcoma protuberans, and pilar leiomyoma.

Figure 1.

Typically, specimens of dermatomyofibroma extend to the superficial subcutis and have been reported on occasion to extend into the deeper subcutis. The adnexal structures are usually spared.

Special staining of histologic specimens of dermatomyofibroma is most often useful to rule out other similarly presenting lesions, rather than rule in the diagnosis. Dermatomyofibroma stains negatively with desmin, h-caldesmon, S-100, and epithelial membrane antigen. These stains are helpful to differentiate other tumors that may be in the differential such as neurofibroma, desmoplastic spindle cell nevus, extraneural spindle cell perineurioma, and smooth muscle tumors. These lesions will stain only focally positive for actins or CD34.

There is little value in imaging studies or serologic tests in known cases of dermatomyofibroma.

Diagnosis confirmation

The differential diagnosis of dermatomyofibroma is broad and includes the following entities: connective tissue nevus, cutaneous myofibroma, dermatofiboma, dermatofibrosarcoma protuberans, desmoplastic spindle cell nevus, extraneural spindle cell perineurioma, fibrous hamartoma of infancy, hypertrophic scar, neurofibroma, pilar leiomyoma, smooth muscle tumors. Some of these entities will be distinguished by clinical history, presence at birth, recent trauma, etc; however, histologic diagnosis is paramount.

Who is at Risk for Developing this Disease?

Dermatomyofibroma typically occur in young to middle-aged females, with rare reports of lesions in children and males. Dermatomyofibroma are rare lesions in and of themselves. It has been theorized that dermatomyofibroma in male children may regress spontaneously after childhood more often than in females.

What is the Cause of the Disease?

Etiology

Pathophysiology

The etiology of dermatomyofibroma is unknown, but it is described as a benign proliferation of fibroblasts and myofibroblasts.

Systemic Implications and Complications

Currently, there are no known systemic implications of dermatomyofibroma. These lesions are rare enough, however, that such a correlation would be very difficult to recognize.

Treatment Options

Treatment options for dermatomyofibroma are summarized in the Table 1.