The mediastinal tumor samples taken from our patient stained positively for vimentin, muscle-specific actin, and desmin and were negative for cytokeratin AE 1/3, cytokeratin 7, cytokeratin 20, epithelial membrane antigen (EMA), calretinin, S100 protein, melanoma antibody (HMB45), and leukocyte common antigen.
Immunohistochemistry according to the avidin-biotin-peroxidase technique (10) using antibodies against vimentin (monoclonal, 1:400; Dako Corporation, Carpinteria, Calif), leukocyte common antigen (monoclonal, 1:200; Dako), UCHL-1 (monoclonal, 1:200; Dako), CD3 (monoclonal, 1:200; Dako), CD20 (monoclonal, 1:200; Dako), CD30 (monoclonal, 1:20; Dako), EMA (monoclonal, 1: 10 000; Dako), and S100 protein (polyclonal, 1:200; Dako) was performed on 4-[micro]m-thick sections of paraffin-embedded tissue blocks from both breast and axillary lesions.
[ILLUSTRATION OMITTED] Immunohistochemically, the cells were focally positive for vimentin; diffusely and strongly positive for immunoglobulin (Ig) A (Figure 3, A) and [Kappa] light chains (Figure 3, B); and negative for IgG, IgM, [Lambda] light chains, leukocyte common antigen, CD20, cytokeratin, S100, HMB45, and smooth muscle antigen.
The tumor was also studied by means of electron microscopy and immunohistochemical stains against keratins (human cytokeratin high-molecular-weight MO630, Dakopatts A/S, Glostrup, Denmark), epithelial membrane antigen (E29, Dako), leukocyte common antigen (2B11 +PD7/26, Dako), vimentin (V9, Dako), neuron-specific enolase (BBS/NC/VI-H14, Dako), synaptophysin (SY38, Dako), and chromogranin A (DAK-A3, Dako).
