Fig. 2

Representative images of dedifferentiated carcinoma and rhabdoid undifferentiated carcinoma. Case 17 was a typical dedifferentiated carcinoma and showed the coexistence of normal glands, well-differentiated adenocarcinoma components, and undifferentiated components at low magnification (A, arrows, × 40). The undifferentiated components showed reduced expression of SMARCA2 (B, × 200) and intact expression of ARID1A (C, × 200). Case 8 was a typical rhabdoid undifferentiated carcinoma and showed a non-cohesive sheet-like growth pattern at low magnification (D, × 100). The neoplastic cells presented polygonal or round with abundant eosinophilic cytoplasm, and the nuclei were large and vacuolated with prominent nucleoli at high magnification (G, ×400). SMARCA2 and ARID1A showed a complete loss, accompanied by strong staining of the surrounding lymphocytes (E, F, ×200), while SMARCA4 and SMARCB1 showed diffuse intense staining (H, I, ×200)