Figure 1.

Carboxypeptidase-M (CPM) is selectively expressed in epithelioid cells (EPCs) of common lung granulomatous diseases. Identical microscopic fields of granulomatous lung lesions are shown for comparative macrophage-labeling patterns with the use of anti-CPM (right panel) and common macrophage-immunohistochemistry (MA-IHC) reference markers (middle). The disease types are indicated on the hematoxylin–eosin (H–E)-stained photographs (left). (a) The EPCs of sarcoidosis are distinctly labeled with CPM, including the multinucleate cell (arrow). The staining pattern is similar with CD68, although the latter decorates additional non-granulomatous macrophages (arrowheads). (b) Granuloma (arrows) obtained from early active tuberculosis shows CPM expression, including the multinucleate macrophages (encircled) and the labeling is restricted to EPCs, as opposed to pan-macrophage marker CD163, which stains other macrophages as well (middle panel, arrowheads and lower-right), (c) In contrast, palisade epithelioid cells of advanced tuberculosis, which are labeled intensively with CD68, are basically negative for CPM. Note that some of the multinucleate cells, however, still express CPM (slim arrows), but others are nearly non-reactive (thick arrows). IHC stainings for a were visualized with VIP (purple), and for b and c with diaminobenzidine (DAB) (brown) peroxidase chromogenic substrates, respectively. Nuclear counterstains are methyl green or hematoxylin.