The histologic appearance of corticosteroid injection sites

The deposits of short-acting corticosteroids in connective tissue were studied in surgical specimens removed from 12 patients. Microscopically, the deposits appeared as circumscribed collections of acellular, finely granular material that stained faintly with hematoxylineosin. Special stains were not particularly helpful. In six patients, a mild to moderate reaction of histiocytes, fibroblasts, and lymphocytes was seen at the edges of the deposits. The attendant tissue reaction was relatively avascular. In one patient, a granulomatous reaction resembling a rheumatoid nodule was noted. No reaction was found in five patients. The changes did not significantly vary with the type of corticosteroid, dosage, time interval between injections, etc. All deposits contained small, elongate spaces, and, in two cases, also contained clusters of birefringent crystals. The distribution, shape, and size of the crystals resembled those of the empty spaces around them. These observations indicate that corticosteroid deposits can be recognized in conventional histologic sections and should be differentiated from other lesions in connective tissue.