label: Alveolar Soft Part Sarcoma
label_lc: alveolar soft part sarcoma
description: A rare malignant neoplasm characterized by the presence of large epithelioid cells with abundant cytoplasm forming nests and pseudoalveolar structures. The groups of the epithelioid cells are separated by thin-walled sinusoidal spaces. It occurs most often in adolescents and young adults. In adults the most common sites of involvement are the extremities, and in infants and children, the head and neck. It usually presents as a slowly growing mass and it frequently metastasizes to other anatomic sites. The most common sites of metastasis are the lungs, bone, and brain.