Alveolar soft tissue sarcoma

A rare soft tissue sarcoma characterized by a slowly growing, painless space-occupying lesion, composed of large, uniform, epithelioid cells arranged in solid nests and/or alveolar structures, separated by thin, sinusoidal vessels. The tumor mostly affects adolescents and young adults. Early metastasis, most commonly to the lung, bones, and brain, is a characteristic feature and relevant prognostic factor, together with age at presentation and tumor size, while histological features have no prognostic significance.