Gastrointestinal stromal tumor

Pathology:

MACROSCOPIC DESCRIPTION:
    (A) Stomach tumor ? GIST:  A nodular tumor 140 x 135 x 115mm. The serosal
    surface is irregular with a small amount of gastric mucosa attached at one  edge
    50 x 40 x up to 6mm thick. There are  disruption  in  the  capsule  that  appear
    consistent with removal of adhesions but there is one irregular area 35  x  25mm
    where the tumor appears to become adherent  to  brown  tissue.  The  tumor  is
    partly necrotic with hemorrhagic material in the center.  There  is  a  rim  of
    viable tumor at the periphery of the lesion up to 20mm thick.
    Representative section A1-A6.  A1-A2: viable areas  of  tumor.  A3-A4:  gastric
    mucosa attached. A5: adhesion. A6: tumor.
   
    MICROSCOPIC DESCRIPTION:
    A spindle cell growth, with striking nuclear palisading. In  certain  areas  the
    spindle cell palisades appear to be oriented around a central blood vessel.  The
    spindle cells otherwise form nests and  fascicles.  The  spindle  cells  possess
    delicate cytoplasmic processes, most evident in areas of edema. The  growth  is
    accompanied by a rich vasculature, many vessels thrombosed, and  multiple  areas
    of necrosis or hemorrhage in various stages of organization. The tumor is seen
    to have expanded subserosally, with fibrous adhesion of spleen (slide A5). Fatty
    tissue is also attached to the outer gastric  surface.  Little  inflammation  is
    seen in the gastric mucosa. 10 - 15 mitotic figures per 50 high power fields are
    seen in the tumor.
    Immunohistochemistry (block A6):
    ckit: intense cytoplasmic expression, including paranuclear accentuation of  the
    signal.
    actin: negative.
            
    DIAGNOSIS:
    
    Gastrointestinal stromal tumor. According to tumor size and mitotic rate,  the
    expected chance of recurrence is high