Sections of the tumor in the right lung showed lobular structures formed by thick fibrous bands (Figure 5). There was an admixture of neoplastic epithelial cells and non-neoplastic lymphocytes (Figure 6). The epithelial cells were polygonal with vesicular bland nuclei and inconspicuous nucleoli. The lymphocytes were small and uniform, and were scattered among the tumor cells. Mitosis was rare. Immunohistochemically, the epithelial cells were positive for cytokeratin stain (CAM 5.2 and AE1/AE3), and showed an arborizing network of interconnecting cell processes (Figure 7). The lymphocytes were negative for cytokeratin. In contrast, the leukocyte common antigen (LCA) stained lymphocytes positive but the epithelial cells were negative (Figure 8). The tumor was negative for calretinin. The results of various immunostains are summarized in Table 1. All thoracic lymph nodes examined were free of tumor.
Sections of left and right ventricles revealed an extensive transmural infiltration of eosinophils, lymphocytes, macrophages and scattered multinucleated giant cells, accompanied by patchy myocyte necrosis (Figures 9 and 10). These inflammatory infiltrates were negative for cytokeratin stain.