Figure 1. Histological and immunohistochemical features of the first excised subcutaneous lesion showing the LPL-associated amyloidoma. At low power, the abundant amorphous, glassy pink material permeating the fibro-fatty subcutaneous tissue is readily appreciable (A: Hematoxylin and eosin (H&E) ×20) and it appears intimately admixed with a patchy cellular infiltrate (B: H&E ×50). A higher-power view (C: H&E ×200) allows identification of a mixed population of small lymphocytes, plasma cells, and plasmacytoid lymphocytes, with numerous Dutcher bodies (inset: ×600). Peripherally, one can also notice multinucleated giant cells of foreign body type surrounding thin-walled vessels (D: H&E ×100). Immunohistochemical (IHC) studies confirm the presence of a dual population of small CD20+ B lymphocytes (E: CD20 IHC ×200) and MUM1+ plasmacytic-differentiated elements (F: MUM1 IHC ×200). The whole lymphoplasmacytic population shows Ig κ light-chain restriction (G: Ig k IHC ×400), as well as restricted IgM production (H: IgM IHC ×200) with strong cytoplasmic positivity in the plasma cell component and weaker membranous positivity in the lymphocytic plus plasmacytoid component (inset: ×600, with a nicely stained Dutcher body); IgM immunoreactivity can also be appreciated in the interspersed acellular material.