Salivary Gland Neoplasms: Oncocytoma

Oncocytomas are rare tumors that constitute only 2.3% of benign epithelial salivary gland neoplasms.

• They are most often encountered after the sixth decade of life with a nearly equal male-to-female ratio of occurrence.
  
• The majority of these tumors affect the parotid gland (78%), few affect the submandibular gland (9%), none are reported in the sublingual gland and minor salivary gland involvement is most often in the palate, buccal mucosa or tongue.

The clinical presentation of oncocytomas is essentially identical to other benign salivary tumors—a slowly growing, nontender mass, typically in the superficial lobe of the parotid. They are firm, may be multilobulated and mobile on exam. Oncocytomas, along with Warthin’s tumors, have been noted to demonstrate increased uptake of pertechnetate anion and therefore can be distinguished from some other neoplasms by using technetium-99m pertechnetate scintigraphy.

Gross pathology findings include a homogenous tumor with a smooth surface that may be divided into lobules by fibrous tissue septae. Microscopically, there are sheets, nests or cords of uniform oncocytes. These cells are large with distinct borders and filled with an acidophilic granular cytoplasm. The granularity of the cytoplasm is due to the presence of large numbers of mitochondria that may constitute up to 60% of the cell volume.

Special staining procedures such as the phosphotungstic acid hematoxylin stain, Bensley’s aniline-acid fuchsin or Luxol-fast-blue reaction take advantage of this unique characteristic and can help to make the diagnosis of oncocytoma, as can electron microscopy.

Standard treatment of oncocytomas is surgical excision with a margin of normal tissue. There is an exceedingly low rate of recurrence of these tumors if removal is complete. Enucleation or curettage is not appropriate.

Category: Pathology Notes