Systemic vasculitis might present as a tumorlike lesion that initially could misdirect the correct diagnosis and the appropriate medical treatment. The aim of the present study is to summarize all reported cases of tumorlike presentation in systemic vasculitides, in order to have comprehensive data on the characteristics of this unusual phenomenon. We report 4 cases of systemic vasculitis presenting as a tumorlike lesion. In addition, we performed a MEDLINE search of all English-language papers published from 1966 to 1999, looking for vasculitis presenting as tumorlike lesion. Details were included concerning vasculitis classification, specific characteristics, location of the "tumor," the presence or absence of systemic involvement, and whether surgery was performed before diagnosis. Seventy-nine cases of vasculitis presenting as a tumorlike lesion were found in the literature, in addition to the 4 new cases described. The average age of the reported cases was 50.5 +/- 15.8 years, and 51% were female. In 82% of the cases the "tumor" was associated with constitutional symptoms and elevated erythrocyte sedimentation rate (ESR). The most common vasculitis categories with tumorlike presentation were Wegener granulomatosis (WG; 28 cases) and giant cell arteritis (GCA; 17 cases). In almost half the patients, surgery was performed before diagnosis. All patients with GCA presented with either a breast or an ovarian tumor. The most common location of a tumorlike lesion was the breast (22%), followed by central nervous system lesions (16%). Other frequent locations were the ovary (10%), caused exclusively by GCA and polyarteritis nodosa (PAN), and the male genitourinary system, almost all caused by PAN. Including vasculitis in the differential diagnosis of a tumorlike lesion might lead to an earlier diagnosis and consequently to prompt and appropriate treatment, avoiding needless operations. Constitutional symptoms and elevated ESR should alert clinicians to the possible diagnosis of vasculitis rather than a tumor. The association of GCA with ovarian pseudotumor is distinct and has not been emphasized before. We therefore suggest that GCA should be included in the list of differential diagnosis of an ovarian or breast tumor in an elderly woman, particularly when systemic symptoms and parameters of inflammation are present.