Sclerosing polycystic adenosis

Sclerosing polycystic adenosis (also abbreviated SPA) is a rare salivary gland tumor first described in 1996 by Dr. Brion Smith.[1] The major salivary glands, specifically the parotid gland (about 70% of cases) and the submandibular gland, are affected most commonly.[2][3] Patients usually come to clinical attention with a mass or swelling in their salivary glands in the 5th decade of life, with females affected much more commonly than males.[1][2] Nearly all of the cases reported so far have a benign behavior (no recurrence and no metastasis), although there is a single case that has had an associated malignant transformation (becoming an invasive cancer).[4]

Low power H&E stained image of parotid gland sclerosing polycystic adenoma

When reviewed by a pathologist, the findings are quite similar to fibrocystic changes of the breast, although they are different enough, that it is now recognized to actually represent a true neoplasm (clonal proliferation) through various studies.[5] Specifically, the lesions are usually well-circumscribed, containing lobules of haphazardly arranged ducts, myoepithelial cells, and acini that have abundant sclerosing or hyalinized fibrosis. Apocrine change is quite common in the ductal cells.[6] The ducts range from small ductules to cystically dilated spaces (more than 4 striated duct-widths across), often containing products of secretion or reactive histiocytes. A very curious and characteristic finding in all of the lesions is the presence of bright pink (eosinophilic) acinar granules (which are altered zymogen).

High power H&E stained image of a parotid sclerosing polycystic adenoma with eosinophilic granules