Clear cell tumors of the lower respiratory tract.

Clear cell tumors of the lower respiratory tract comprise a diverse group of lesions. The prototypical lesion is the benign clear cell tumor or "sugar tumor," a tumor of enigmatic histogenesis, whose name derives from the high glycogen content of the cells. Analogous to the salivary gland lesion of the same name, acinic cell tumors may also occur in the tracheobroncheal tree. The topic of "clear cell carcinoma" is discussed, which in the opinion of the authors does not constitute a distinct tumor entity. A discussion of potential lesion metastatic to the lung with clear cell histology is also presented. Histological details of the various entities are discussed, as well as the significant histochemical, immunohistological, and electron microscopic features; in particular, such findings that are relevant to differential diagnosis are stressed, including the distinction of primary and metastatic lesions.