[Lymphoepithelial cyst of the thyroid coexistent with amyloid goiter].

A case of amyloid goiter in a 73-year-old man with systemic amyloidosis complicating long lasting rheumatoid arthritis is reported. The thyroid gland was massively infiltrated with amyloid and contained foci of fat tissue and epithelial solid cell nests. Incidentally, a cyst lined by squamous epithelium, with small amount of lymphocytes in the subepithelial stroma was found. This cyst fulfilled the criteria for the diagnosis of a lymphoepithelial cyst presumably of branchiogenic origin. The herein described case of simultaneous occurrence of branchiogenic cyst and amyloid goiter represents, to our best knowledge, a unique coexistence of these two entities. The possible relationship between these lesions and their differential diagnosis is discussed.