What immune cells are typically found in the histological features of vaccine-induced sarcomas?

Vaccine-induced sarcomas are a recognized complication associated with certain vaccines in small animals, particularly in cats. The histological features of these sarcomas often reveal a prominent infiltrate of foamy macrophages. These specialized immune cells arise from the chronic inflammatory response to the vaccine's materials or adjuvants, leading to a characteristic histopathological appearance.

Foamy macrophages are notable for their lipid-laden cytoplasm, which is a result of their phagocytic activity and the processing of necrotic tissue and cellular debris within the sarcomatous lesion. The presence of these macrophages is indicative of a delayed hypersensitivity reaction and ongoing inflammation, which is a key aspect of the pathogenesis of these tumors. Recognizing the infiltration of foamy macrophages in tissue samples is critical for pathologists in diagnosing vaccine-associated sarcomas and differentiating them from other neoplastic processes.

The other immune cells listed do not typically play a significant role in the histological features seen in vaccine-induced sarcomas. For instance, neutrophils are commonly involved in acute inflammatory responses, eosinophils often react to parasitic infections and allergies, while basophils are associated with allergic reactions and inflammation, none of which primarily