Interobserver agreement among expert pathologists on through-the-needle microforceps biopsy samples for evaluation of pancreatic cystic lesions

Background and aims: The recent development of microforceps for EUS through-the-needle biopsy (TTNB) sampling of the wall of pancreatic cystic lesions (PCLs) allows the collection of histologic specimens never handled and evaluated before by pathologists. We aimed to estimate the interobserver agreement among pathologists in evaluating such samples.

Methods: TTNB specimen slides from 40 PCLs with worrisome features were retrieved and independently evaluated for specimen adequacy, presence of lining epithelium, grade of epithelial dysplasia, presence of ovarian type stroma, and specific diagnosis by 6 expert pathologists from 6 different tertiary care centers. The Gwet's AC1 was used to assess interobserver agreement.

Results: An almost perfect agreement was observed for specimen adequacy (AC1, .82; 95% confidence interval [CI], .79-.98), presence of lesional epithelium (AC1, .90; 95% CI, .86-.92), epithelial dysplasia (AC1, .97; 95% CI, .95-.99), and ovarian-like stroma (AC1, .90; 95% CI, .86-.93). When considering all diagnoses separately, a moderate to substantial agreement was observed (AC1, .62; 95% CI, .57-.67), similarly to mucinous cysts versus serous adenoma versus other diagnoses (AC1, .65; 95% CI, .59-.70) and for mucinous cysts versus all other diagnoses (AC1,.74; 95% CI, .68-.84). The agreement for diagnosis of mucinous cystic neoplasm versus intraductal mucinous papillary neoplasm was almost perfect (AC1, .88; 95% CI, .81-.95).

Conclusions: Interobserver agreement between expert pathologists in the evaluation of TTNB samples from PCLs with worrisome features was close to perfection for all evaluated parameters, except definitive diagnosis. When mucinous cystic lesions were compared versus all other diagnoses, the agreement became substantial, thus indicating that TTNB specimens can provide important information for PCL management decisions.