Comment:  Nodular episcleritis (aka nodular fasciitis) is a non-neoplastic proliferation of spindle shaped cells on the eye (cornea or sclera), eyelids or skin. The cause of this lesion is unknown, but a reactive or inflammatory process has been suggested. Biologically, nodular episcleritis is slow growing but can behave like a low grade fibrosarcoma showing both local invasiveness and recurrance following surgical removal.

The lesion has been reported in several breeds of dog, but German Shepherds appear to be predisposed.

The lesions are usually composed of plump spindle shaped cells that are heavily infiltrated by inflammatory cells. These cells are most often lymphocytes and plasma cells, but neutrophils, eosinophils, macrophages, and multinucleated giant cells have also been reported. Reticulin fibers are prominent within these tumors. Collagen fibers are less frequently seen.

a. The cells in the photomicrograph are mostly plump spindle-shaped cells with abundant eosinophilic cytoplasm and large euchromatic nuclei arranged in whorls and sheath-like bundles. Clusters of inflammatory cells, mainly lymphocytes and plasma cells are scattered throughout.

b. Area of the mass have prominent pockets of interstitial ground substance.

 c. Focal areas of vacuolization were also noted