Pleomorphic adenoma: parotid gland
Slowly-enlarging right neck mass.
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Parotidectomy and histology images described individually.
Pleomorphic adenomas arising in the parotid gland usually have a pink-tan rubbery surface, well-defined pushing margins, and translucent areas of cartilaginous differentiation (as seen in this image). A rim of uninvolved salivary gland parenchyma is present around the tumor in this superficial parotidectomy specimen.
- Pleomorphic adenomas often have a biphasic appearance caused by admixture of epithelium and stroma. The epithelial component here is arranged in tubular and glandular structures. The stroma has myxochondroid appearance
- Microscopically, the pleomorphic adenomas consist of three elements: epithelial cells, myoepithelial cells, and stroma. The epithelial cells commonly form tubular or glandular structures and are surrounded by myoepithelial cells. The background stroma may be myxoid, chondroid, hyalinized, or vascular
- Pleomorphic adenomas arising in the parotid usually have a thick fibrous capsule as seen here. The normal parotid tissue is to the upper right of the capsule and the tumor is on the lower left. The capsule can be variable in thickness and may even be absent. Pleomorphic adenomas arising in the minor salivary glands are well-demarcated but usually not encapsulated
Fine needle aspiration biopsy was consistent with a pleomorphic adenoma. The diagnosis was confirmed in the parotidectomy specimen above.
Pleomorphic adenoma accounts for 70% to 80% of all neoplasms of salivary glands and it involves the parotid gland in almost 80% of cases. It is usually well-circumscribed and has pushing borders. The gross appearance depends upon the relative proportion of epithelial elements and stromal component which may range from myxoid to cartilage. Tumors with a prominent cartilaginous matrix have bluish-gray opalescent appearance as seen in this case.
This case has been reproduced with permission from Dharam M. Ramnani, MD's collection at WebPathology.com. Additional images are here.