Histology of gastrointestinal stromal tumor (GIST) of mixed spindle cell and epithelioid type

Biopsy specimen of a mixed-type GIST stained with hematoxylin and eosin (H&E).
(A) At low power (4x), note the abrupt transition between spindle and epithelioid areas, as indicated by the arrows.
(B) As shown with higher magnification (20x), the tumor is composed of elongated spindle cells as well as rounded epithelioid cells.