Example 3 Continued
Comment: Crystal formation has been described in 21 cases of lymphoplasmacellular B-cell disorders including multiple myeloma, light chain deposition disease, solitary plasmacytoma, plasmacytoid lymphoma, and paraproteinemia. Crystals are rod-shaped, rhomboid, square, or rectangles of different sizes. Although heavy chains varied (alpha, gamma, or mu), 18 of the 20 cases in which the light chain was identified were kappa type and only two lambda type [1-8]. The crystals were usually found in plasma cells as well as macrophages and sometimes other organs. The crystals apparently develop in secondary lysosomes as a result of digestion of ingested immunoglobulin. Only one report identified the composition of the crystals as dimers of the variable region of kappa light chains . Their ultrastructure varies from homogeneous and electron lucent or dense  to lattice-like to fibrillar [1, 9].
1. Takahashi K, Naito M, Takatsuki K, Kono F, Chitose M, Ooshima S, Mori N, et al. Multiple myeloma, IgA k type, accompanying crystal-storing histiocytosis and amyloidosis. Acta Pathol Jpn 1987; 37:141-154.
2. Kapadia S, Enzinger F, Heffner D, Hyams V, Frizzera G. Crystal-storing histiocytosis associated with lymphoplasmacytic neoplasms. Report of three cases mimicking adult rhabdomyoma. Am J Surg Pathol 1993; 17:461-467.
3. Grossniklaus H, Stulting R, L'Hernault N. Corneal and conjunctival crystals in paraproteinemia. Hum Pathol 1990; 21:1181-1183.
4. Kjeldsberg C, Eyre H, Totzke H. Evidence for intracellular amyloid formation in myeloma. Blood 1977; 50:493-504.
5. Jennette J, Wilkman A, Benson J. IgD myeloma with intracytoplasmic crystalline inclusions. Am J Clin Pathol 1981; 75:231-235.
6. Cordier A, Scolari L, Vaerman J-P, Dutrieux-Fauchet M-C, Dutrieux C, Haumont S. Ultrastructural aspects of crystal-like inclusions in a case of IgA plasma cell proliferation. Scand J Haematol 1976; 17:143-152.
7. Yamamoto T, Hishida A, Honda N, Ito I, Shirasawa H, Nagase M. Crystal-storing histiocytosis and crystalline tissue deposition in multiple myeloma. Arch Pathol Lab Med 1991; 115:351-354.
8. Tsuchikawa K, Yokomichi H, Satoh I, Suzuki C, Watanabe Y, Tajima G. A Study of intracytoplasmic inclusions in myeloma cells from two patients with multiple myeloma. Tohoku J Exp Med 1987; 153:11-20.
9. Raman S, van Slyck E. Nature of intracytoplasmic crystalline inclusions in myeloma cells (morphologic, cytochemical, ultrastructural, and immunofluorescent studies). Am J Clin Pathol 1983; 80:224-228.
Clinical summary Example 4
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