Pathologic interpretation of endoscopic ultrasound-guided fine needle aspiration cytology/biopsy for pancreatic lesions

Abstract

Pathologic interpretation of endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) cytology/biopsy specimens is one of the most challenging tasks in cytology and surgical pathology practice, as the procedure often yields minimal amounts of diagnostic material and contains contaminants, such as blood cells and normal intestinal mucosa. EUS-FNA cytology/biopsy will nevertheless become a more popular procedure for evaluation of various pancreatic lesions because they are difficult to approach with conventional endoscopic procedures. Pathologists should understand the structural differences and limitations of EUS-FNA that make pathologic diagnosis difficult. Ancillary tests are available for differential diagnosis of EUS-FNA for various pancreatic lesions. Immunostains are the most commonly used ancillary tests, and pathologists should able to choose the necessary panel for differential diagnosis. Pathologists should review clinical history and radiologic and/or EUS findings before selecting an immunostain panel and making a pathologic diagnosis. In addition, one's threshold of malignancy should be adjusted according to the appropriate clinical setting to avoid under-evaluation of pathologic diagnoses. Clinico-pathologic correlation is essential in pathologic evaluation of EUS-FNA for pancreatic lesions. Pathologists can reduce errors by correlating clinical and radiologic findings when evaluating EUS-FNA. Some molecular tests can be applied in differential diagnosis of pancreatic neoplastic and cystic lesions. Molecular data should be used as supportive evidence of a specific disease entity, rather than direct evidence, and should be correlated with clinico-pathologic findings to avoid errors in pathologic diagnosis.

Keywords: Endoscopic ultrasound-guided fine needle aspiration; Pancreatic neoplasms; Pathology.

Fig. 1.

(A). Normal gastric mucosa in conventional cytology smear shows nests of monotonous cells with smooth boundaries. (B) Normal duodenal mucosa showing scattered goblet cells in conventional cytology smear (Pap smear).

Fig. 2.

(A) Ductal adenocarcinoma showing scattered atypical cell nests with complex papillary architecture and necrotic background on biopsy slide. (B) Well differentiated ductal adenocarcinoma cell nest, mimicking normal mucosa, is more hypercellular on conventional cytology smear (Pap). (C) A few atypical tumor cells in a fibrinous background on biopsy slide. Although it does not include necrotic tumor cell debris, the cytologic atypia is sufficient for a diagnosis of malignancy, especially when clinical or radiologic evaluation strongly suggests a malignancy. (D) Tuberculous inflammation shows aggregates of granuloma without viable tumor cells in conventional cytology smear.

Fig. 3.

Intraductal papillary mucinous neoplasm. (A) A mucinous background is seen on conventional cytology smear. (B) A papillary epithelial nest showing high-grade dysplasia on conventional cytology smear.

Fig. 4.

(A) Well-differentiated neuroendocrine tumor cells show the characteristic salt-and-pepper chromatin pattern on conventional cytology smear. (B) On biopsy, well-differentiated neuroendocrine tumor cells show diffuse nest-like arrangement of monotonous nuclei with mild atypia. (C) Scattered epithelioid cells with hyperchromatic nuclei and abundant cytoplasm may be seen in well-differentiated neuroendocrine tumors. (D) Poorly differentiated neuroendocrine carcinoma shows scattered hyperchromatic nuclei.

Fig. 5.

(A) Scattered solid pseudopapillary neoplasm cells show discohesive organoid pattern with vesicular nuclei. (B) Solid pseudopapillary neoplasms show myxoid pseudopapillae with scattered plasmacytoid cells.

Fig. 6.

(A) Metastatic renal cell carcinoma shows clear to granular cytoplasm on endoscopic ultrasound–guided fine needle aspiration (EUS-FNA) biopsy. (B) Metastatic small cell carcinoma from the lung exhibited discohesive small round cells with molding pattern on EUS-FNA biopsy.