Proliferative Fasciitis : Microscopic
Proliferative fasciitis is composed of a uniform population of stellate and spindle fibroblasts and myofibroblasts with a tissue culture appearance. The background consists of an admixture of myxoid and collagenous stroma. In that regards, it resembles nodular fasciitis. This process extends along the interlobular septa of subcutaneous tissue. The distinguishing feature of proliferative fasciitis is proliferation of large ganglion-like myofibroblasts with large vesicular nuclei and prominent nucleoli. They are present singly or in clusters. They have abundant granular basophilic cytoplasm. Unlike nodular fasciitis, multinucleated giant cells are rare. Pediatric cases of proliferative fasciitis are rare. They tend to be more circumscribed and may have a lobular growth pattern. In addition, they show several features not seen in adult lesions, including greater cellularity, less amount of collagenous and myxoid matrix, more numerous mitoses, and the presence of acute inflammation and necrosis.