Figure 3. Loss of MAX protein expression can be present in cell subpopulations in early GISTs but is present in all cells from affected metastatic GIST.

Haematoxylin and eosin stains (a,c,e,g) and MAX IHC (b,d,f,h): case 67 with wild-type MAX (a,b) has retained MAX expression; case 29 (c,d), low-risk GIST with MAX mutation, has diffuse loss of MAX expression; case 3 (e,f), intermediate-risk GIST, has mosaic loss of MAX expression with admixed MAX-positive and MAX-negative cells; case 51 (g,h), metastatic GIST with MAX mutation, has diffuse loss of MAX expression. Positive internal controls for MAX expression in all cases are scattered inflammatory cells and fibrovascular cells, and—in case 51—a lymphoid aggregate at the upper left. Scale bar, 50 μm.