Sarcomatoid carcinomas are typically (but not always) biphasic tumors containing both carcinomatous and sarcomatous components. Within the upper aerodigestive tract, they arise from the mucosa and are predominantly composed of pleomorphic spindled cells associated with squamous carcinoma, the latter often presenting focally at the tumor base. Although their histogenesis is still debated, most authors favor metaplastic origin of the sarcomatous cells from carcinoma cells. Indeed, when studied with electron microscopy and/or immunohistochemistry the sarcomatous cells are frequently found to retain epithelial features; however, the sarcomatous metaplasia can be so complete that malignant cartilage, bone, and/or muscle cells are formed. In addition, metastatic deposits may contain sarcomatous and/or carcinomatous components. Sarcomatoid carcinomas are potentially aggressive tumors and should be treated accordingly. Although it is difficult to predict biologic behavior in every case, patients whose tumors are deeply invasive tend to have a poor prognosis, whereas those with superficially invasive tumors usually have an excellent prognosis.