670 Arch Pathol Lab Med—Vol 126, June 2002 FNAB Specimen Misinterpretation—Young et al Misinterpretation of Normal Cellular Elements in Fine-Needle Aspiration Biopsy Specimens Observations From the College of American Pathologists Interlaboratory Comparison Program in Non-Gynecologic Cytopathology Nancy A.Young, MD; Dina R. Mody, MD; Diane D. Davey, MD ● Context.—The College of American Pathologists Interlab- oratory Comparison Program in Non-Gynecologic Cyto- pathology is a popular educational program for nongyne- cologic cytology, with 1018 participating laboratories by the end of 2000. Data generated from this program allow tracking pathologist performance in a wide variety of lab- oratory practices. Objective.—To review performance of participating pa- thologists in making patient diagnoses with fine-needle as- piration biopsy specimens, with particular interest in the false neoplastic diagnoses (both benign and malignant neo- plasms) that were submitted for benign aspirates contain- ing only normal cellular components. Design.—We reviewed the diagnoses made from 1998 through 2000 by participating pathologists through the use of glass slides containing benign fine-needle aspiration bi- opsy specimens of the liver, kidney, pancreas, and salivary gland that contained only normal cellular components. Results.—The false neoplastic rate for kidney (60%) was the highest, followed by liver (37%), pancreas (10%), and salivary gland (6%).These rates are much higher than what has previously been reported in the literature. Conclusions.—This study illustrates that normal cellular elements are a significant pitfall for overinterpretation of fine-needle aspiration biopsy specimens. (Arch Pathol Lab Med. 2002;126:670–675) F ine-needle aspiration biopsy (FNAB) is a well-estab- lished technique for the diagnosis of neoplasms in both superficial and deep-seated organs. Most series studying the accuracy of salivary gland, 1–14 pancreas, 15–25 kidney, 26–28 and liver 20,21,29–41 report rare to no false-positive results. However, most of these series are from academic or large-volume cytopathology practices with extensive experience in nongynecologic cytology. The College of American Pathologists (CAP) Interlaboratory Comparison Program in Non-Gynecologic Cytopathology (NGC) pre- sents a great opportunity to track pathologist performance in a wide variety of laboratory practices. Data generated from this survey identify discrepant diagnoses in each ref- erence diagnosis category. We reviewed the performance of participating pathologists on FNAB specimens of the liver, kidney, pancreas, and salivary gland, with particular interest in the false neoplastic diagnoses (both benign and malignant neoplasms) that were submitted for benign as- pirates containing only normal cellular components. MATERIALS AND METHODS The NGC program consists of quarterly shipments of 5 glass slides of nongynecologic material with accompanying clinical Accepted for publication January 17, 2002. From the Department of Pathology, Fox Chase Cancer Center, Phil- adelphia, Pa (Dr Young); Department of Pathology, Baylor College of Medicine, Houston, Tex (Dr Mody); and Department of Pathology and Laboratory Medicine, University of Kentucky, Lexington, Ky. Reprints: Nancy A.Young, MD, Department of Pathology, Fox Chase Cancer Center, 7701 Burholme Ave, Philadelphia, PA 19111 (e-mail: nayoung@fccc.edu). histories. The program is structured similarly to the CAP Inter- laboratory Comparison Program in Cervicovaginal Cytology but is strictly educational and not graded. Cases were contributed by the members of the CAP Cytopa- thology Resource Committee and reviewed at several screening sessions for consensus, quality of the preparation, and adequacy before inclusion into the program. Both Papanicolaou- and Ro- manowsky-stained slides were accepted. Each accepted slide had to be diagnostic on its own, since participants would receive only 1 slide per case. Cases involved both exfoliative cytologic and FNAB specimens from a variety of body sites. This study spe- cifically reviewed performance on fine needle aspirates of the liv- er, pancreas, salivary gland, and kidney sites. Initially, bench FNAB specimens (which tend to be more cellular than in vivo aspirates) were accepted into the program. These are being re- tired from the program as they come up for review and new ones are not being accepted. By the end of 2000, 1018 laboratories had subscribed to the program, including 2497 pathologists and 1899 cytotechnologists. Most laboratories were in the United States. However, a few in- ternational laboratories also subscribe to this program. The diagnostic menu was provided to participants using a bubble answer format. The program answer sheet consisted of 2 parts. The first part was the general diagnostic category, which was divided into 4 series: benign or negative for malignant cells (this category includes benign neoplasms and infectious condi- tions and normal material), suspicious for malignant cells, posi- tive for malignant cells (including neuroendocrine lesions such as carcinoid tumor), and unsatisfactory. The second part was the specific diagnostic menu for each giv- en organ or tissue site. Each diagnosis had a specific code. The participant reviewed the slide along with the accompanying clin- ical information to select the appropriate answer from the diag- nostic menu. Laboratories submitted responses from individual