A benign tumor that is usually solitary, painless, palpable mass that is firm in consistency and slightly movable and often fluctuant. It can occur in any location, but tends to involve the muscles of the thighs, buttocks, and shoulders. On microscopic examination, there is abundant mucoid material and relative hypo cellularity and loose reticulin fibers. Vascular structures are sparse. The cells have a stellate shape with small hyper chromatic pyknotic nuclei and scanty cytoplasm. Some myxomas may show focal areas of hyper cellularity. However absence of nuclear atypia, mitotic figures or necrosis helps to rule out malignancy. [from
HPO]