Figure 4

(a) Prostate cancer cases with discordant PTEN immunohistochemistry and FISH results on initial review. Case #9: PTEN immunohistochemistry demonstrates very weak cytoplasmic immunostaining with loss of nuclear immunostaining and thus was called negative on initial review, though in retrospect, it may be better classified as ambiguous because of weak staining and absence of benign glands for comparison (left). Four-color FISH image from an adjacent section that is representative of all examined cores in this tissue microarray (right) indicates that the PTEN gene does not have a detectable deletion by FISH. The enlarged inset shows that the centromeres, WAPAL, PTEN, and FAS gene probes are each present as two copies. Case #10: PTEN immunohistochemistry image (left) shows heterogeneous PTEN loss in some tumor glands (arrow), but PTEN protein is expressed by the majority of other tumor glands in this core. FISH image from an adjacent section (right) was initially read as PTEN intact, but shows a focal area with hemizygous PTEN deletion recognized on re-examination guided by immunohistochemistry. The enlarged inset shows that there is only one copy of the red PTEN gene probe (one red signal) and loss of both aqua FAS gene probes. Case #11: PTEN immunohistochemistry image (left) demonstrates heterogeneous PTEN loss in some tumor glands (arrows) but not in others (arrowheads). FISH image from an adjacent section (right) shows the small area of the section that had a homozygous PTEN deletion on re-examination. The enlarged inset shows that there are no copies of the red PTEN gene probe and one copy of the aqua FAS gene probe, but retention of the adjacent WAPAL and centromere probes. (b) Prostate cancer cases with discordant PTEN immunohistochemistry and FISH results on initial review. Case #12: PTEN immunohistochemistry image (left) shows heterogeneous loss of PTEN protein in some tumor glands (arrow) but not in others (arrowhead). A FISH image from an adjacent section that is representative of all examined cores in this tissue microarray (right) indicates that the PTEN gene does not have a detectable deletion by FISH. The enlarged inset shows that the centromeres, WAPAL, PTEN, and FAS gene probes are each present as two copies. The heterogeneous loss in this case may have resulted in different tumor areas sampled in slides for immunohistochemistry and that for FISH. Case #13: PTEN immunohistochemistry image (left) shows predominantly intact/light immunostaining in tumor glands (arrowhead) and benign glands (b) with a very focal area of tumor with PTEN loss identified on re-review after FISH analysis (arrowhead, inset). FISH analysis of an adjacent section to the immunohistochemistry indicates a homozygous PTEN deletion. The enlarged inset shows that there are no copies of the red PTEN gene probe and loss of one green WAPAL gene probe but retention of both the FAS and the centromere probes.