[388] Diagnostic Value of DOG-1 Expression in Fine-Needle Aspiration Cytology of Gastrointestinal Stromal Tumors (GISTs)

SB Bokhari, JF Silverman, YL Liu. Allegheny General Hospital, Pittsburgh, PA

Background: DOG-1 is a newly introduced immunohistochemical (IHC) marker that is useful in the diagnostic evaluation of GISTs. DOG-1 gene transcripts were originally identified as a typical finding in gene expression profiling studies on GISTs. The corresponding protein has been recently identified as a calcium-regulated chloride channel protein, encoded by a locus at chromosome 11q13. The utility of DOG-1 as an immunohistochemical marker has very recently been established in the surgical pathologic evaluation of suspected GISTs. It has been shown that DOG-1 immunohistochemistry should be added into the diagnostic panel evaluating surgical pathology specimens from suspected GISTs, especially those GISTs that are C-Kit (CD117) negative. However, there is a lack of data regarding the diagnostic usefulness of DOG-1 in fine-needle aspiration (FNA) cytology of suspected GISTs.
Design: A total 22 cases of GISTs with FNA cytology smears and corresponding cell blocks were retrieved from the hospital computer system. All cases were confirmed by histology with immunohistochemical studies. DOG-1, CD117, and CD34 IHC was performed on cell blocks that were formalin-fixed, paraffin embedded and stained using a heat-induced epitope retrieval technique.
Results: 19/22 patients (86.4%) had GISTs that were CD117 positive and DOG-1 positive. Of those 19 patients, 4/19 (21.1%) were CD34 negative. 3/22 patients (13.6%) had GISTs that were DOG-1 positive and CD117 negative. Of those 3 patients, all were positive for CD34. DOG-1, CD117, and CD34 all showed membranous and cytoplasmic staining. Of the cases that were DOG-1 and CD117 positive, DOG-1 showed stronger staining versus CD117.
Conclusions: Our results indicated that DOG-1 is a sensitive and specific marker in diagnosing GISTs in FNA cytology specimens, especially in C-kit negative cases. We believe that an IHC panel consisting of CD117, DOG-1 and CD34 is very useful to confirm a diagnosis of GIST in FNA cytology and can confirm the diagnosis of GIST in C-kit negative cases.
Category: Cytopathology

Monday, March 22, 2010 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 46, Monday Morning


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