Sarcomatoid carcinomas of the upper aerodigestive tracts.

Sarcomatoid carcinoma of the upper aerodigestive tract continues to be one of the most difficult diagnostic challenges for surgical pathologists. Histogenesis has been settled in favor of a divergent (mesenchymal) differentiation of a carcinoma, most often a squamous cell carcinoma. Finding the carcinoma and/or its immunohistochemical marker in the metaplastic cells establishes the diagnosis. There are, however, lesions that can simulate sarcomatoid carcinomas to varying degrees, and in which neither a definable carcinoma nor immunohistochemical evidence of one can be found. Such lesions fall into several categories: 1. benign reactive lesions, 2. inflammatory myofibroblastic tumors, 3. sarcomas, usually low-grade, 4. atypical pseudosarcomatous proliferation. The clinicopathologic considerations of sarcomatoid carcinomas are presented in this context and include immunohistochemical findings, prognostic factors, and biologic course.