Plasmacytoma and bronchoalveolar carcinoma in Il12rb2 KO mice. A 21-month-old mouse showing a mature lymph node plasmacytoma with cells characterized by low nuclear-cytoplasmic ratio and abundant cytoplasm (A). Some mitoses are observed (A, arrow). Plasmacytoid cells express CD138 (B), CD43 (C), and CD56 (D). Panels E and F show amyloidosis detected in the liver (F, Congo red staining) and kidney (G, Giemsa staining) from 2 plasmacytoma-bearing mice. A 22-month-old mouse has developed bronchoalveolar carcinoma of the lung. This epithelial tumor is formed of well-differentiated mucin-containing columnar cells lining the respiratory spaces (G). Magnification: (A-G) × 630; (H) × 400.