Upper image immunostained for Caveolin shows very strong cytoplasmic  positivity in a small group of cells. Myofibres show a moderate membraneous positivity.

Immunostaining with anti beta Catenin ( lower image) shows strong intercalated disc positivity in myofibres but, membraneous positivity in the cells that exhibit strong cytoplasmic Caveolin positivity.

What cells are these?