In Situ Interleukin-6 Transcription in Embryonic Nonmuscle Myosin Heavy Chain Expressing Immature Mesenchyme Cells of Cardiac Myxoma

Cardiac myxomas are benign tumors which sometimes secrete interleukin-6 (IL-6), however, the pathogenesis and the IL-6 secreting cells are not clear. There are vascular myosin heavy chain isoforms; SM2 expression is specific to mature smooth muscle cells, while SMemb is a nonmuscle-type isoform which is expressed in immature mesenchyme cells. We hypothesized that immature mesenchyme cells play pivotal roles in the secretion of IL-6; we studied these expression in resected samples of myxoma. SMemb expression was increased but SM2 expression was not in the channels of myxoma. Increased IL-6 transcription was observed in the SMemb expressing cells in the channel. Therefore, mesenchyme cells with immature phenotype in the channel play pivotal roles of inflammation and pathogenesis of cardiac myxoma. Cardiol Pathol 2000;9:33–37