[IgG4-related salivary gland lesions]

To provide the demographic, clinical, laboratory, radiological, morphological, and immunomorphological characteristics of IgG4-related sialoadenitis (IgG4-S), which allow the differential diagnosis with neuroendocrine, granulomatous, blood cancer lesions of the salivary gland (SG).

In the period 2004 to 2014, IgG4-S was diagnosed in 32 (11%) out of 289 patients with significantly enlarged parotid and submandibular glands (PG and SMG). Only 4 (9%) patients had isolated IgG4-related disease (IgG4-D) whereas involvement of a few organs ran as an IgG4-SD systemic disease in 29 (91%) patients.

There was a slight preponderance of women with a median onset age of 42 years. Enlargement of the SMG (52.7%), lesions of the nasal cavity and paranasal sinuses (37.2%), and enlargement of the lacrimal gland and orbital pseudotumors (31%) are the most common clinical manifestations at disease onset. A follow-up study indicated that along with involvements of SMG (97%), PG (72%), eye sockets (72%), nasal cavity and paranasal sinuses (56%), one third of the patients were found to have generalized lymphadenopathy, to frequently develop pulmonary, hepatic, pancreatic, renal injuries; and the disease ran within IgG4-SD. The laboratory manifestations were characterized by moderate eosinophilia and elevated blood IgE levels in one-third of the patients and by moderately higher erythrocyte sedimentation rate and hypergammaglobulinemia in 50%. The increased blood level of IgG (84%) and its subclass IgG4 (86.4%) is an indication for further verification of IgG4-D in patients with involvement of the major SG. Immunohistochemical examination, by measuring the concentration of IgG4-secreting plasma cells (PCs), and determination of B-cell clonality in biopsy specimens should be done to verify a diagnosis with IgG4-D.

The determination of blood IgG4 (>2 g/l) in patients with considerably enlarged major SG may suggest the presence of IgG4-S. Minimally invasively incised PG and SMG biopsies with their subsequent morphological and immunomorphological examinations should be performed to make an accurate diagnosis. More than 40% of IgG4-secreting PCs detected in SG tissue is evidence to diagnose IgG4-D.