PKCθ utility in diagnosing c-KIT/DOG-1 double negative gastrointestinal stromal tumors

Background: The aim of this study was to evaluate the diagnosis value of an immunohistochemical (IHC) panel of three antibodies for the diagnosis of gastrointestinal stromal tumors (GISTs). Material and methods: In 80 consecutive GISTs without lymph node metastases, the IHC examinations were performed using the antibodies CD117 (c-KIT), DOG-1 and c-theta (PKC theta) protein. The diagnostic value of PKC theta in c-KIT/DOG-1 negative GISTs has been explored in fewer than 10 Medline-indexed papers. Results: The c-KIT, PKC theta and DOG-1 positivity was noted in 92.50% (n = 74), 90% (n = 72) and 76.25% (n = 61) of the cases, respectively. All of the C-KIT negative cases (n = 6) were also DOG-1 negative but displayed PKC theta positivity. All of the DOG-1 positive cases (n = 61) also expressed c-KIT. No correlation between the examined markers and clinicopathological parameters was noted. Conclusions: The PKC theta sensitivity is similar to c-KIT and superior to DOG-1 sensitivity. All of the c-KIT/DOG-1 negative GISTs seem to express PKC theta. For a proper diagnosis of GIST, the c-KIT/DOG-1/PKC theta panel should be used, with possible therapeutic but not prognostic value.