Abstract
Granuloma annulare (GA) is a benign, self-limiting entity. Hands, arms, feet and legs are the most common locations. Histologic variants are necrobiotic or collagenolytic (NGA), interstitial or incomplete (IGA) and sarcoidal or tuberculoid (SGA). They demonstrate different histologic patterns, the topic of this study. Rarely, granuloma annulare has an associated malignancy, so-called PGA. In this study, we compare histopathologic differences between GA and PGA. We retrospectively reviewed patient charts between 01/01/2006 to 10/31/2020. Cases that were previously diagnosed with GA over the age of 18 were selected. We identified GA cases previously diagnosed with hematologic or solid organ malignancy (SOM) without any time limitations. Twenty-eight cases that met these criteria were included in the study. The median age was 66 (40-93). The most common location was extremities (upper 15/54%, lower 6/21%). Sixteen cases were associated with SOM (57%), seven cases were associated with hematologic malignancy (25%) and five cases were associated with both hematologic and SOM (18%). Microscopic examination revealed IGA (20/71%) was the most common type, followed by NGA (4/14%). Multinucleated giant cells were present in 4 of NGA (80%) and 5 of IGA cases (25%) and mucin was prominent in 12 of IGA and 4 of NGA cases. Eosinophils were only observed in 5 of the cases (NGA:2, IGA:2, SGA:1). Perivascular inflammation was noted in most cases (NGA:5, IGA:18, SGA:1). PGA is a rare entity that mostly affect older population. Histologically, PGA resembles classic GA. There are no significant differences to distinguish them. In the literature, most common type of PGA was IGA followed by NGA. Also, most common classic GA pattern was IGA, followed by NGA. In a previous study, perivascular inflammation was observed in PGA. Another study revealed classic GA also showed perivascular inflammation. The unique finding in our study was presence of multinucleated giant cells.Financial Disclosure: No current or relevant financial relationships exist.