DOG1, a transmembrane
calcium-regulated
chloride channel protein, is a sensitive and specific marker for
gastrointestinal stromal tumors compared with other spindle cell and epithelioid
neoplasms. Overexpression has also been described in a variety of both benign and
malignant epithelial neoplasms. Recently, DOG1 immunoreactivity has been reported in pancreatic solid pseudopapillary
tumors (SPT), suggesting a role as a marker for SPT. Utilizing immunohistochemistry, we evaluated DOG1 expression in
pancreatic neoplasms to determine the prevalence of staining and establish diagnostic utility. Multiple tissue microarrays (TMA) were created from cores of
formalin-fixed
paraffin-embedded blocks containing pancreatic
adenocarcinomas (n=112),
neuroendocrine tumors (n=99),
serous cystadenomas (n=28), and SPT (n=14) as well as normal pancreas (n=12). Immunoreactivity for DOG1 (clone K9) was assessed for intensity (1 to 3+), percentage of
tumor positivity and location. Of the 99 cases of
neuroendocrine tumors, only 2 (2%) were focally positive. Patchy staining was identified in 8 cases (7%) of
adenocarcinoma of 1 to 2+ intensity, involving 15% to 80% of the
tumor cells and primarily seen in a membranous and
luminal distribution. In contrast to a previous report, no DOG1 positivity was observed in SPT, evaluated by both TMA and full sections. The TMAs of
serous cystadenomas and normal pancreas were negative for DOG1. Rarely, pancreatic islets displayed granular, cytoplasmic staining. DOG1 antibody clone K9 is not a useful marker for SPT or other primary
pancreatic neoplasms. Additional studies may be helpful to evaluate differences between clones of DOG1.