Hepatic lipogranulomas in canine visceral leishmaniasis: Morphological and immunohistochemical characterization using IBA-1 and MAC387

Abstract

Hepatic involvement is common in canine visceral leishmaniasis (CVL), yet uncommon inflammatory patterns remain poorly documented. This retrospective study aimed to describe the occurrence, histopathological features and immunohistochemical characterization of hepatic lipogranulomas in dogs naturally infected with Leishmania spp. Liver samples from 30 necropsied dogs with confirmed leishmaniasis (between 2010 and 2025) and 60 control dogs without leishmaniasis were evaluated histologically. Cases containing lipogranulomas and/or epithelioid granulomas were further assessed using periodic acid–Schiff and Prussian blue histochemical stains. Leishmaniasis cases were subjected to immunohistochemistry (IHC) for Leishmania spp, and those containing lipogranulomas were also subjected to IHC for IBA-1 and MAC387. Hepatic lipogranulomas, defined as aggregates of lipid-rich foamy macrophages, were identified in 5/30 (16.7%) dogs with leishmaniasis. These lesions were distributed randomly within the hepatic parenchyma and portal regions and contained intracytoplasmic pigment that was consistently PAS positive and variably Prussian blue positive. Foamy macrophages were consistently IBA-1 positive and MAC387 negative. Amastigotes were detected in all livers containing lipogranulomas and, in two cases, were observed within foamy macrophages. In an age-matched control group, lipogranulomas were identified in 2/60 dogs (3.3%) compared with 5/30 (16.7%) in the leishmaniasis group (Fisher's exact test, P = 0.039; odds ratio = 5.68). These findings expand the recognized histopathological spectrum of hepatic lesions observed in CVL and support the recognition of hepatic lipogranulomas as one of the inflammatory patterns that may occur in some infected dogs, while recognizing that they are not restricted to CVL.