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Image of the Week
Edited and moderated by Stacey Mills, MD, Pathology Network's Image of the Week Blog is a forum for the discussion of interesting and often diagnostically challenging pathology images.
Thursday, February 06, 2014
Incidental Parotid Gland Lesion
A 54-year-old woman underwent a superficial parotidectomy for a mass lesion that was interpreted as a typical mixed tumor ("pleomorphic" adenoma).  This lesion is not illustrated.  In the surrounding parotid gland the incidental lesion shown below was noted. 
What is your diagnosis?

The photomicrographs show a loose aggregate of ducts lined by cytologically uniform cells with a low-columnar to cuboidal appearance.  The ducts have the histologic appearance of normal intercalated ducts and this finding has been referred to as intercalated duct hyperplasia.  Larger forms of this process, often with a peripheral capsule, have been referred to as intercalated duct adenomas, though the distinction between the two is often arbitrary and hybrid forms clearly exist. 
These small, incidental proliferations can be seen in adjacent normal salivary (usually parotid) tissue removed for other reasons, though it was not until relatively recently that they were well-documented in the literatue in an article by Weinreb and colleagues in 2009 (Am J Surg Pathol 2009;33:1322-9).  The authors note that although these small lesions can occasionally be found in salivary tissue removed for any reason, there appears to be an association with basal cell adenomas and epithelial-myoepithelial carcinomas, suggesting that the intercalated duct lesions could be precursors for other more important forms of salivary neoplasia.  
Further studies will be necessary to more firmly establish an association with clinically significant neoplasia.  In the mean time, keep an eye out for these nodules in salivary tissue adjacent to a more obvious tumor, and I bet you'll find them.  And now you know what to call them!
About the Author

Stacey E. Mills, MD
Stacey E. Mills, MD, a graduate of University of Virginia (UVA) and the UVA Medical Center, has authored nearly 230 articles, 20+ books, atlases and monographs—including the renowned Sternberg's Diagnostic Surgical Pathology. He has been a practicing Professor and Staff Pathologist at UVA for 30+ years and is Director of Surgical Pathology and Cytopathology. His clinical specialty is general surgical pathology with emphasis on neoplasms and neoplasm-like lesions. Dr. Mills is also Editor-in-Chief of The American Journal of Surgical Pathology.