The determination of tumor cell estrogen receptor (ER) expression status by immunohistochemical analysis has become standard practice, yet assay reproducibility has not been assessed adequately. By using a breast cancer tissue microarray, we examined interlaboratory variability in ER reporting. A 2-fold redundant tissue microarray block was created from 29 breast cancers. Unstained slides were distributed to 5 laboratories, and each laboratory immunostained and scored 1 slide for ER. Interlaboratory agreement ranged from moderate to high (overall kappa = 0.54 for 0-3+ grading; overall kappa = 0.84 for negative vs positive assessment of ER status). When 1 observer scored each of the 5 slides, interlaboratory agreement was slightly better (kappa = 0.63 for 0-3+ scoring; kappa = 0.96 for negative vs positive scoring). One laboratory, which had used an antibody and antigen retrieval method different from the others, demonstrated only fair concordance with the other 4 laboratories, but there was substantial intralaboratory interobserver agreement and excellent agreement with an outside observer reviewing the slide stained in that laboratory. The tissue microarray was an efficient and effective tool for identifying variability in ER reporting and should prove valuable in other external quality assurance programs.

Herein is reported the cytologic features of four cases of cystic neoplasms of the pancreas as seen in fine-needle aspirates. Cytologically, the cases fall into two distinct groups: mucinous cystic neoplasm and serous cystadenoma. The aspirates from the mucinous cystic neoplasms characteristically showed columnar mucus-secreting epithelial cells, some of which were arranged in a papilloglandular pattern, with abundant mucous material in the background. The aspirates from the serous cystadenoma yielded small sheets of cuboidal cells with small nuclei and clear cytoplasm, without a background of mucous material. This cytologic division corresponds closely to the histologic classification proposed by Compagno and Oertel and hence is of prognostic and therapeutic value. The diagnostic challenges confronted by the cytopathologist are (1) to differentiate neoplastic cysts from the inflammatory pseudocysts; (2) to differentiate neoplastic epithelium from the normal epithelium of the bowel and pancreatic ducts; and (3) to differentiate mucinous cystic neoplasms from serous cystadenomas.

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