Antischkow cells are seen in -

Aschoff body (Fig. 15.13): It is spheroidal or fusiform characteristic lesion seen in rheumatic disease. Site: During acute RF, may be found in any of the three layers, in the perivascular interstitial region of the hea. Formation of Aschoff body consists of 3 phases: Early/exudative phase: It consists of a perivascular focus of swollen eosinophilic collagen surrounded by lymphocytes, plasma cells, and macrophages. Intermediate/granulomatous phase: It is pathognomonic of rheumatic myocarditis. It is a granulomatous lesion, with a central fibrinoid focus associated with lymphocytes (primarily T-cells), macrophages, Anitschkow cells (pathognomonic for RF) and occasional plasma cells. Anitschkow cells are plump activated macrophages, which have abundant cytoplasm. They have round-to-ovoid nuclei in which the chromatin is disposed of in a central, slender, wavy ribbon. These nuclei resemble a caterpillar when cut longitudinally (hence known as "caterpillar cells"). On cross section, these nuclei have an owl-eye appearance. Few Anitschkow cells may become multinucleated (with 2 to 4 nuclei) in which case, they are termed Aschoff giant cells. Late/healed /final phase: Aschoff body is replaced by a nodule of scar tissue.