Sclerosing Polycystic Adenosis of Major Salivary Glands. A Clinicopathologic Analysis of Nine Cases

We describe nine cases of a histologically distinct and previously unreported lesion of the major salivary glands. The patients ranged in age from 12 to 63 years and included four males, five females. The lesions were slow-growing masses in the parotid gland (eight cases) and submandibular gland (one case). The clinical impression in each case was a benign salivary gland tumor. Grossly, the lesions were discrete, pale, rubbery nodules embedded within the salivary gland parenchyma. Microscopically, the lesions were unencapsulated, circumscribed masses of sclerotic and hyalinized collagenous tissue. Irregularly distributed throughout the collagenous tissue in a vaguely lobular pattern were hyperplastic ductal and acinar elements that were usually accompanied by cystically ectatic ducts. The dilated ducts frequently showed apocrine-like metaplasia and epithelial hyperplasia, which often formed transluminal bridges in a cribriform pattern. This epithelial hyperplasia sometimes surrounded eosinophilic globules as seen in so-called collagenous spherulosis. The combination of fibrosis, epithelial hyperplasia, and cystic changes were reminiscent of fibrocystic changes of the breast. Focally, acinar elements contained large, intensely eosinophilic, periodic acid-Schiff's-positive, intracytoplasmic granules believed to represent altered zymogen granules. A sparse to focally intense lymphocytic infiltrate accompanied the epithelial proliferations. Previous interpretations of these masses have included mucoepidermoid carcinoma, low-grade adenocarcinoma, benign adenoma, and mixed tumor. The limited available follow-up suggests that this process has a favorable prognosis despite recurrences in two cases. It is postulated that these lesions represent a pseudoneoplastic condition that results in both fibrosis and epithelial proliferation. We suggest the term sclerosing polycystic adenosis for these rare lesions.