Histological parameters helpful in recognising steroid-treated temporal arteritis: an analysis of 35 cases

To establish the histological and immunohistochemical parameters that are helpful in recognising temporal arteritis in patients who have been treated with steroids before biopsy, and to analyse the clinical features and correlate them with the histological findings.

A retrospective review of charts of 35 patients treated with steroids before obtaining temporal artery biopsy specimens, spanning a 11-year period from 1995 to 2005. The study was conducted at the Ophthalmic Pathology Laboratory, Cullen Eye Institute, Houston, Texas, USA. The clinical features were evaluated and correlated with the histopathological findings. Each case was evaluated with respect to age, sex, race, clinical findings, erythrocyte sedimentation rate, corticosteroid dosage (oral versus intravenous) and the duration of treatment. The time interval between obtaining the biopsy specimen and the onset of steroid treatment was carefully recorded for each patient. In selected cases, histiocytic markers (CD-68 and HAM-56) were used to identify the presence of epithelioid histiocytes, which characterises a granulomatous inflammation. Other immunohistochemical studies (CD3, CD20, CD4, CD8, CD45RO, CD45RA and S-100 protein) were performed in selected cases to characterise the inflammatory cells.

The three most reliable histopathological parameters of corticosteroid-treated temporal arteritis are the following: (1) complete or incomplete mantle of lymphocytes and epithelioid histiocytes located between the outer muscular layer and the adventitia; (2) large circumferential defects in the elastic lamina (best seen with the Movat's pentachrome); and (3) absent or few small multinucleated giant cells. In some cases the main artery appears normal, whereas the primary branches show evidence of a healing arteritis. The histological findings vary according to the duration of treatment before obtaining the biopsy specimen.

Striking histological differences can be recognised objectively between patients with active (untreated) giant cell arteritis and patients who have been treated with corticosteroids. The earliest histopathological changes were detected by the end of the first week after steroid treatment (usually after day 4 to the end of the first week). The histological findings were more difficult to recognise at 2-3 months after steroid treatment. Ophthalmic and general pathologists should be able to recognise this entity on the basis of the histological findings including the special stains and results of immunohistochemical studies (CD-68 and HAM-56).