Dermatomyofibroma (plaque-like dermal fibromatosis) represents a distinct clinicopathological entity in the spectrum of cutaneous mesenchymal neoplasms showing a myofibroblastic line of differentiation.

 Age: Occurs mostly in adolescents and  young adults. These benign neoplasms occur frequently, but not exclusively, in young women.

Site: Shoulder girdle, axilla and abdomen

Gross:  Firm red- brown plaques or nodules 1- 2 cm in diameter. Keloid like and linear variants may occur.

Microscopic features:  

Histologically, these are non-encapsulated but well-circumscribed, plaque-like lesions located in the reticular dermis.

The tumour is composed of bland spindle-shaped tumour cells containing an ill-defined, pale eosinophilic cytoplasm and elongated, neuroid nuclei. Neoplastic cells are arranged in bundles and fascicles orientated parallel to the skin surface. The fascicles are separated from the epidermis by a Grenz zone.

There is no evidence of cytologic atypia and mitotic figures are infrequent.

The adnexal structures are spared and elastic fibres are increased and fragmented. The lesion may extend to the upper part of the subcutaneous septa in some cases.

Immunohistochemistry:   Tumour cells express vimentin and variably muscle actin and alpha-smooth muscle actin,  but are negative for desmin, CD34, S100, and epithelial markers.
Some dermal dendrocytes stained positively for Factor XIIIa,  but the spindle-shaped cells were negative.

Electron microscopy : Revealed a mixture of fibroblasts, myofibroblasts, and undifferentiated mesenchymal cells.

Differential diagnosis:  Dermatofibroma (fibrous histiocytoma); Pilar leiomyoma ; Neurofibroma ;  Adult myofibromatosis ;  Extra-abdominal fibromatosis ; Hypertrophic scar ;  Plaque-stage dermatofibrosarcoma protuberans.(In dermatomyofibroma- Storiform pattern is not present, pattern of infiltration is limited , Actin positive and CD34 negative) ; Plaque-stage Kaposi's sarcoma - (abundant extravasated erythrocytes, scattered inflammatory cells, numerous capillaries,and sieve-and slit-like spaces may be present in haemorrhagic dermatomyofibroma.The spindled tumour cells are negative for CD34, and HHV8.)

All lesions are treated by conservative excision.

Abstracts: Dermatomyofibroma. A benign cutaneous, plaque-like proliferation of fibroblasts and myofibroblasts in young adults. J Cutan Pathol. 1992;19(2):85-93. Haemorrhagic dermatomyofibroma (plaque-like dermal fibromatosis): clinicopathological and immunohistochemical analysis of three cases resembling plaque-stage Kaposi's sarcoma.Histopathology. 2003 ;42(6):594-8. Dermatomyofibroma: report of two cases.J Cutan Pathol. 1994;21(4):371-6. Linear dermatomyofibroma. Clin Exp Dermatol. 1996;21(4):307-9. Dermatomyofibroma (Plaqueformige Dermale Fibromatose). J Dermatol. 1997;24(12):793-7. Dermatomyofibroma: case report and review.Pediatr Dermatol. 1999 Nov-Dec;16(6):456-9. Differences between plaque-like variants of dermatofibrosarcoma protuberans and plaque-like dermal fibromatosis (dermatomyofibroma).] Hautarzt. 1994;45(5):299-303. Dermatomyofibroma: a report of two cases, one occurring in a child. Australas J Dermatol. 2001 ;42(1):22-5.        Your Ad Here Custom Search