Bacillary angiomatosis is a reactive vascular proliferation caused by Bartonella - a family of gram-negative bacilli (B. henselae, B. quinitana, B. baciliformis, B. elizabethae). The patient usually has compromised immune system (usually a male with AIDS). The image shows capillary-caliber vessels lined by plump endothelium with clear cytoplasm, mild atypia, and occasional mitotic figures. The interstitium shows a neutrophilic infiltrate.
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