Massive crystal-storing histiocytosis associated with low-grade malignant B-cell lymphoma of MALT-type of the parotid gland.

Massive crystal deposition is unusual in lymphoproliferative disorders. In this report, a mucosa-associated lymphoid tissue (MALT) low-grade B-cell lymphoma of the parotid gland containing large numbers of crystal-storing histiocytes is described. The patient, an 81-yr-old female, presented with a history of long-standing left parotid gland enlargement. FNA cytology of the tumor showed a lymphoplasmacytic infiltrate and sheets of large benign histiocytes with abundant eosinophilic intracytoplasmic inclusions. Paraffinsection immunohistochemistry performed on the cell block demonstrated that the histiocytic cells were immunoreactive for the KP-1 (CD-68) antibody and monotypic for cytoplasmic IGM and L-light chain. The cytological diagnosis was consistent with a low-grade B-cell lymphoma with plasmacytic differentiation associated with crystal-storing histiosis. A periparotid lymph node was biopsied and showed involvement by a monocytoid B-cell lymphoma with plasmacytic differentiation and crystal-storing histiocytosis in the pericapsular region.