Fig. 4

Microscopic features. a. Microcystic pattern of the tumor before chemotherapy (HE, ×400); b. solid pattern of the tumor before chemotherapy (HE, ×400); c. solid pattern of the tumor in the mastectomy specimen (HE, ×400); d. the pushing border near the skin shown in the mastectomy specimen (HE, ×100); e. morphological changes of tumor cells after chemotherapy (HE, ×400); f. isolated tumor cell was detected in axillary lymph node (HE, ×400); g. Positive cytoplasm and nuclear staining for S-100 by IHC (Envison, ×400) ; h. Positive cytomembrane staining for E-Cadherin by IHC (Envison, ×100); i. Positive nuclear staining for Ki-67 by IHC (Envison, ×400); j. Negative staining for SMA by IHC (Envison, ×400); k. Positive PAS staining of the extracellular secretory material (×400); l. ETV6-NTRK3 fusion arrangement indicated by FISH analysis