The diagnosis of C-kit negative GIST by PDGFRA staining: clinical, pathological, and nuclear medicine perspective.
BACKGROUND
Gastrointestinal stromal tumors (GIST) comprise a majority of tumors previously diagnosed as gastrointestinal leiomyomas, leiomyoblastomas, and leiomyosarcomas. Although GIST may be identified by light microscopy, pathologists commonly employ a panel of immunohistochemical markers to confirm the morphological impression including anti-CD34, smooth-muscle actin, desmin, S100, and CD-117. However, in CD- 117 negative cases, it becomes difficult to diagnose GIST. This is of great importance, since the use of imatinib mesylate has led to a dramatic improvement in survival rates of GIST patients besides improved quality of life.


METHODS
We report the case of a 67-year-old male patient diagnosed as having chemotherapy-resistant metastatic leiomyosarcoma. We reviewed the specimen for a possible diagnosis of c-kit negative GIST. Platelet derived growth factor receptor-alpha (PDGFRA) immunohistochemical stain was recommended. The specimen was positively stained for PDGFRA. Imatinib mesylate (400 mg/d) was started. The patient showed an excellent response after receiving imatinib treatment which was documented with 18 fluoro-deoxyglucose positron emission tomography and computed tomography (18F-FDGPET/ CT) prior to and after treatment.


CONCLUSIONS
The importance of diagnosis of c-kit negative GIST is emphasized while stressing the importance of PDGFRA staining besides PET/CT response evaluation.
Department of Medical Oncology, Gaziantep Oncology Hospital, Gaziantep, Turkey. sevinc@gantep.edu.tr
Alper
A
Sevinc
Celalettin
C
Camci
Mustafa
M
Yilmaz
Hakan
H
Buyukhatipoglu
D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D046152:Gastrointestinal Stromal Tumors / Q000175:diagnosis* / Q000378:metabolism*; D006801:Humans; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods*; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000032:analysis*; D013194:Staining and Labeling / Q000379:methods
D014408:Biomarkers, Tumor; D019009:Proto-Oncogene Proteins c-kit; D020796:Receptor, Platelet-Derived Growth Factor alpha