Metastatic small blue cell tumors are small to medium-sized cells with round nuclei and scant cytoplasm.
Plasma cells can mimic osteoblasts with their eccentric nuclei, abundant blue cytoplasm, and prominent perinuclear hoffs; however, plasma cell nuclei should show the characteristic chromatin pattern (i.e., clock-face nucleus) and have perinuclear rather than central cytoplasmic hoff.
Osteoblast cells are medium-sized to large “plasmacytoid” cells with small oval nuclei, vesicular chromatin, indistinct nucleoli, abundant cytoplasm, and prominent central cytoplasmic hoffs (pale Golgi zones).
Metastatic carcinoma cells will be clustered, but should be large, pleomorphic cells with high nuclear to cytoplasmic ratio and hyperchromatic, irregular nuclei with or without prominent nucleoli.
Endothelial cells usually appear as spindle-shaped cells with small nuclei either singly or in elongated clusters.
