Sialolithiasis. Differential diagnostic problems in fine-needle aspiration cytology

Sialolithiasis with obstruction of major salivary gland ducts can lead to clinical tumefaction related to cystic dilatation. In addition to mucus accumulation, these pseudoneoplasms feature hyperplasia and squamous metaplasia of the ductal lining epithelium, with varying degrees of inflammation. The authors report five examples of this lesion aspirated from two males and three females ranging in age from 45 to 80 years (median 65 years). Three were in the submaxillary gland, and two were in the parotid. In three cases, stone fragments were identified, and diagnoses of sialolithiasis were rendered; two of these patients underwent surgical excision. The remaining two cases showed prominent foam cells and metaplastic squamous cells in a mucoid background that mimicked low grade mucoepidermoid carcinoma. Stone fragments were not identified and a differential diagnoses of sialolithiasis versus low grade mucoepidermoid carcinoma were suggested. Surgical excision revealed sialolithiasis in both instances. When stone fragments are identified in aspirated material, these cases pose little diagnostic difficulty. However, when this material is not present, epithelial changes and mucus accumulation may be difficult to distinguish from low grade mucoepidermoid carcinoma. Cautious interpretation is suggested in this setting.