A 73-year-old woman with a long history of rheumatoid arthritis and polyclonal hypergammaglobulinemia developed a solitary mass in the tongue, which on morphologic and immunohistochemical analyses was consistent with crystal-storing histiocytosis, a rare condition commonly described in association with clonal lymphoplasmacytic disorders. The lesion consisted of a localized collection of histiocytes filled with numerous eosinophilic crystals immunoreactive for both kappa and lambda light chain and gamma heavy chain antibodies. Mature lymphocytes and plasma cells were present both throughout and around the lesion. Since a clonal lymphoplasmacytic neoplasm was ruled out by clinical and immunohistochemical studies, we consider that, in this case, crystal-storing histiocytosis was consequent to polyclonal hypergammaglobulinemia and suggest that this rare histiocytosis is not specific to lymphoplasmacytic neoplasms, but may represent a reaction to high values of normal (or abnormal) immunoglobulins.