S-100 protein expression in a case of elastofibroma dorsi

Elastofibroma is a rare tumorlike process that manifests as slowly growing, solid mass in the subscapular region of elderly persons. Histologically, it is characterized by the presence of fibrous connective tissue in which eosinophilic fibers and globular masses, stained by the elastic tissue stains, are interspersed. We report the immunohistochemical study of the cellular component in a case of subscapular elastofibroma in a 41-year-old man. An unexpected immunoreactivity for S-100 protein was detected in most fibroblast-like cells. S-100 protein expression may be related to a chondroid metaplasia of fibroblast-like cells in response to the continuous traumatic process occuring during the friction between the scapula and the underlying chest wall.