Which histologic findings are characteristic of eosinophilic fasciitis (EF)?

Updated: Dec 24, 2020
  • Author: Peter M Henning, DO; Chief Editor: Herbert S Diamond, MD  more...
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Inflammation, edema, thickening, and sclerosis of the fascia are hallmarks of eosinophilic fasciitis. Acute findings include infiltration of deep fascia and an adjacent subcutis layer with lymphocytes, plasma cells, histiocytes, and eosinophils. Distribution of the eosinophils in the fascia may be focal, and a close relationship appears to exist between blood and tissue eosinophilia. In the deeper portions of the panniculus, a similar infiltrate is found in the fibrous septa and at the periphery of the fat lobules. Deep in the fascia, the inflammatory infiltrate can extend into the epimysium, perimysium, and endomysium. In addition, vascular cuffing with lymphocytes and plasma cells is often seen. [11, 29, 56]

As the disease progresses, inflammatory changes are replaced by generalized sclerosis and thickening of the fascia and adjacent tissue layers. The sclerosis can be dense with hyalinized collagen bands running parallel to the fascia and small foci of fat cells trapped between them. [44, 57] See the image below.

Eosinophilic fasciitis. Top: In this gross specime Eosinophilic fasciitis. Top: In this gross specimen, the dermis (A), subcutaneous adipose tissue (B), and skeletal muscle do not appear unusual. However, the fascia (D) is markedly thickened. Bottom left: The gross findings are recapitulated in this low-power photomicrograph. The epidermis, dermis (A), and subcutaneous adipose tissue are not remarkable in this case. The fascia (D) is markedly thickened and focally infiltrated by inflammatory cells (E). The small amount of skeletal muscle (C) appears normal (hematoxylin and eosin stain at low power). Bottom right: A close-up photograph of a portion of the fascia showing mostly edematous cellular connective tissue (F). It is focally infiltrated by inflammatory cells, including lymphocytes, plasma cells, and histiocytes. The more intensely stained hypocellular pink bands across the top of the field (G) are part of an interstitial exudate of fibrin (hematoxylin and eosin stain at medium power).

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