With modern radiotherapy techniques, clinical radionecrosis is uncommon following eradication of primary squamous cell carcinoma from the larynx. Histologic sections from 265 specimens, prepared by the technique of whole organ subserial step-sectioning were studied to determine the incidence and location of chondronecrosis and/or osteomyelitis in both irradiated and non-irradiated cases. Chondronecrosis occurred in only 1 of 41 early (pT1 - pT2) tumors but in 143 advanced tumors (pT - pT4) treated with radical radiotherapy and containing residual carcinoma, 27% had evidence of significant necrosis, compared with 24% of those not irradiated. Age, sex, tumor grade and previous laryngeal surgery did not appear to be significant factors in the development of necrosis in irradiated patients. The arytenoid cartilage was most frequently involved when chondronecrosis occurred in association with radiotherapy. Six total laryngectomy specimens (3%) were received from patients with symptoms of chondronecrosis and in whom no residual tumor was present. We conclude that although the incidence of clinical perichondritis is low, histologic chondronecrosis and/or osteomyelitis occurred in 26% of all the larynges studied. Radiotherapy appears to be a significant causative factor only in advanced supraglottic tumors.

Ultrastructural studies of pleomorphic adenoma have shown a coordinated differentiation of luminal epithelial and modified myoepithelial cells with the latter cells related to processes resulting in the myxochondroid stroma. Five examples of various histologic types of malignant mixed tumor of parotid origin were examined by electron microscopy to see if underlying patterns of tumor cell differentiation and organization matched those of pleomorphic adenoma. Whether they were intracapsular tumors (with or without identifiable pleomorphic adenoma), carcinomas ex pleomorphic adenoma, or a true malignant mixed tumor, all lesions had cell types and organizations either identical to those in pleomorphic adenoma or, as in less-differentiated examples, displayed features suggesting origin from luminal cells, myoepithelial cells, or both. Even the chondroid cells in the true malignant mixed tumor expressed ultrastructural features indicating their epithelial derivation. On the basis of these findings, some alterations to the classification and terminology of the subtypes of malignant mixed tumor are suggested.

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