What is the pathogenesis of nodular fasciitis (pseudosarcomatous)?

Updated: Oct 07, 2019
  • Author: Guy J Petruzzelli, MD, PhD, MBA, FACS; Chief Editor: Gregory Gary Caputy, MD, PhD, FICS  more...
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Answer

Answer

Pathogenesis

Nodular fasciitis lesions arise in the deep dermis and consist of a haphazard arrangement of immature, spindle-shaped or triangular mesenchymal cells in a feathery pattern within the context of myxoid stroma.

Based on immunohistochemistry studies, the cells in nodular fasciitis lesions stain with smooth muscle–specific actin and desmin, suggesting a myofibroblastic origin of these mesenchymal cells. [68] On the periphery of these lesions, capillary proliferation is abundant and contributes to the extravasated red blood cells that are often intermixed in the stroma. The cells have prominent nucleoli, and mitotic activity is high, corresponding to the rapid growth rate of nodular fasciitis lesions. Because of the immature appearance of the cells and the high mitotic activity, nodular fasciitis lesions can easily be confused with sarcomas. Therefore, proper diagnosis is critical in order to exclude malignancy. [70, 71]


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