CRYSTAL-STORING HISTIOCYTOSIS ASSOCIATED WITH LYMPHOPLASMACYTIC NEOPLASMS - REPORT OF 3 CASES MIMICKING ADULT RHABDOMYOMA

Massive crystal deposition is rare in lymphoplasmacytic (LPc) or plasm a cell neoplasms. We report three cases in which the accumulation of c rystals in histiocytes closely reproduced the histologic features of a dult rhabdomyoma. The patients, all female, aged 18, 77, and 78 years, presented with tumor of cervical lymph nodes (two cases) or the otola ryngic mucosa (two cases). In addition, two patients had monoclonal se rum or urine immunoglobulin (IgM-kappa-1, unknown-1), and one had rena l and bone marrow involvement on biopsy. This last patient died of acu te renal failure at 5 months, another was alive without disease at 8 y ears, and the remaining one was lost to follow-up. Lymph nodes, mucosa e, and kidney showed a neoplastic LPc infiltrate masked by sheets of l arge benign histiocytes containing sheaves of crystals. Paraffin-secti on immunohistochemistry demonstrated monoclonal staining of the LPc ce lls in all cases (IgM-kappa-2, IgA-kappa-1) and of the crystals (IgM-k appa) in one case. In all patients, the crystal-containing cells were positive for KP-1 (CD68), but not for desmin, muscle-specific actin, o r myoglobin. These findings suggest that, in any case of adult rhabdom yoma in which the histologic findings are not typical, a crystal-stori ng histiocytosis should be ruled out: recognition of the atypical LPc component and the histiocytic immunophenotype of the crystal-storing c ells will help prevent a serious misdiagnosis.