Fig. 4

Heterogeneous expression pattern of SMARCA4 and SOX2 in undifferentiated carcinoma (case 21). Two kinds of histological structures were observed in case 21: nested and sheet-like structures (D, arrows, ×20), both of which were composed of undifferentiated neoplastic cells. In the sheet-like structure, neoplastic cells showed a pleomorphic appearance with abundant eosinophilic cytoplasm, and multinucleated tumor giant cells were occasionally observed (A, arrows, ×100). The nested structure was composed of monotonous small round neoplastic cells with poor cohesion, scant cytoplasm, and large nuclei (G, ×100). In sheet-like structure, SMARCA4 was intact (B, ×100) and SOX2 was negative (C, ×100), while in nested architecture, SMARCA4 showed complete loss (H, ×100) and SOX2 showed diffused intense positive expression (I, ×100)