Transformation of monocytoid B-cell lymphoma to large cell lymphoma associated with crystal-storing histiocytes.

We report a case of crystal-storing histiocytosis associated with large cell lymphoma in a patient with a history of monocytoid B-cell lymphoma 10 years previously. The cervical lymph node biopsy showed a diffuse proliferation of large lymphocytes with vesicular nuclear chromatin and distinct nucleoli. These lymphocytes were associated with numerous immunoglobulin lambda light-chain crystal-storing histiocytes, which morphologically resembled rhabdomyoblasts. Occasional lymphoid cells also showed large immunoglobulin crystals. This case establishes the association of crystal-storing histiocytes with lymphomas of mucosa-associated lymphoid tissue and emphasizes the need for immunophenotyping to distinguish these unusual cases from other tumors, particularly adult rhabdomyomas.