A case of adenoid cystic carcinoma associated with IgG4-related disease.

INTRODUCTION: Immunoglobulin G4-related disease (IgG4-RD) is an inflammatory condition associated with elevated serum IgG4 levels and tissue infiltration by IgG4-expressing plasma cells. We present a case of adenoid cystic carcinoma (ACC) of the submandibular gland with possible involvement of IgG4-RD. PRESENTATION OF CASE: The patient was a 59-year-old man presenting with a swollen right submandibular gland. Laboratory tests revealed IgG4 levels of 176mg/dl (reference range: 4.8-105). An initial open biopsy for histological diagnosis showed chronic sialadenitis. The region was monitored on an outpatient basis, and finally the right submandibular was totally resected because malignant tumor could not be excluded. Histological examination of the submandibular gland showed an ACC with lymphocytic infiltration containing many IgG4-positive plasma cells in the tumor stroma. DISCUSSION: We have described a case that indicated a possible involvement of ACC with IgG4-RD. This allows us to speculate that longstanding IgG4-RD may progress to malignancy or infiltration of IgG4-positive plasma cells through the signals of tumor stimuli. Further investigations are required to determine the potential pathogenic mechanism underlying this unique tumor. CONCLUSION: This case underscores that caution is needed in the diagnosis of masses with high serum IgG4 levels, as the differential diagnosis includes malignancy.