A comparative histopathologic study of generalized and localized granuloma annulare

We have reviewed the morphologic findings in 41 histologic slides of granuloma annulare (GA), 15 from localized (LGA) and 26 from generalized granuloma annulare (GGA). The most common pattern was the histiocytic infiltrative type, more so in cases with LGA than with GGA. The palisading granuloma pattern was present in 21.9% of patients and its prevalence was almost equal in both clinical types. The least prevalent histologic type in all patients taken together was the epithelioid nodule type. However, the prevalence of this type in LGA was equal to that of the palisading type, in contrast to that in GGA where it accounted for only 11.5%. In addition, a mixed histologic pattern was found in greater than 25% of sections from GGA and in only one section from LGA. Periodic acid-Schiff stain revealed hyalinized capillary basement membrane in most of GGA and only in approximately 50% of LGA sections. The variation in prevalence of the different histologic patterns between sections from LGA and GGA, and the difference between our findings and those observed in other series, are discussed.