Sjögren's syndrome is a chronic autoimmune systemic disease characterized by polyglandular tissue destruction, leading to keratoconjunctivitis sicca and xerostomia. These patients have 44-fold increased risk of developing salivary gland lymphoma, of which 80% are marginal zone (MALT) type. Having in mind that criteria for distinguishing benign lymphoepithelial lesions from MALT lymphoma are obscure, the aim of this study was to provide practical information that could be integrated into diagnostic practice.
Among 32 parotidectomies, 27 cases were identified as having benign lymphoepithelial disorders and 5 cases low grade MALT lymphoma. Histological sections were stained routinely with hematoxylin and eosin (H&E and special stains. Immunohistochemical study was performed by LSAB2 method, by using primary antibodies for CD20, CD3, Kappa and Lambda light chains and Cytokeratin (Dako Denmark).
The 27 patients with Sjögren's sialoadenitis (22 women and 5 men), and 5 patients with MALT lymphoma (only women) were included in this analysis. According to the Ann Harbor Classification, all patients with MALT lymphoma had stage IE. Both groups of patients had an indolent clinical course, except permanent, rapid parotid enlargement in the patients with MALT lymphoma. Histologically, the periductal lymphoid infiltrate, gradually extended to the acini, completely replacing them by a sea of polyclonal lymphocytes, immunoblasts, germinal centers and plasma cells (confirmed immunohistochemically), but sparing the ducts and preserving lobular appearance. The histological feature of salivary gland MALT lymphoma included heterogeneous B-cell infiltrate that totally or subtotally had effaced the normal glandular structure. Malign lymphoepithelial lesions, representing infiltration of the ductal and epithelial structures by monoclonal neoplastic B-cells, positive for CD20, were highlighted by antibody to cytokeratin.
The optimal diagnosis of salivary gland MALT lymphoma requires careful integration of clinical, morphological and immunohistochemical results.