Context.-The cytologic features of adenocarcinoma/metastatic carcinoma in liver fine-needle aspirates are well described. We review the cytologic findings from 16 aspirates of adenocarcinoma/metastatic carcinoma that were frequently misclassified as hepatocellular carcinomas and compare them with 17 cases that were rarely misclassified.
Objective.-To compare the cytologic features of adenocarcinoma/metastatic carcinoma in fine-needle aspiration specimens of the liver that were frequently misclassified as hepatocellular carcinoma with those of aspirates that were rarely misclassified.
Design.-We reviewed a total of 1712 interpretations from 33 different cases of adenocarcinoma/metastatic carcinoma tumor in liver fine-needle aspiration specimens in the College of American Pathologists Nongynecologic Cytology Program and correlated the cytologic features with performance in the program.
Results.-Overall, cases that were frequently misclassified as hepatocellular carcinoma were misclassified on average 26% of the time (range, 13%-54%), while infrequently misclassified cases were interpreted as hepatocellular carcinoma on average 0.7% of the time (range, 0%-3%). The difference was statistically significant (P
Conclusion.-Cases of adenocarcinoma/metastatic carcinoma with moderate amounts of granular cytoplasm and round nuclei with even chromatin are frequently misclassified as hepatocellular carcinoma. Recognition of this problem, attention to cytologic criteria, and frequent use of immunohistochemical studies and core biopsy may help avoid this pitfall.
(Arch Pathol Lab Med. 2005;129:1217-1221)
The cytologic features of adenocarcinoma/metastatic carcinoma in fine-needle aspiration specimens of the liver are well known1,2 and in general are different than those that have been described for hepatocellular carcinoma.1-14 While it is commonly recognized that some poorly differentiated hepatocellular carcinomas may be difficult to distinguish from adenocarcinoma, difficulty in distinguishing cases of adenocarcinoma/metastatic carcinoma from hepatocellular carcinoma has not been as well described.
The College of American Pathologists (CAP) Nongynecologic Cytology Program is a national educational program that includes cases of adenocarcinoma/metastatic carcinoma. We recently noted that the performance of some cases of adenocarcinoma/metastatic carcinoma in the liver was quite poor, and some of these cases were frequently misdiagnosed as hepatocellular carcinoma. To identify causes for this misinterpretation, the cytologie features of individual cases of adenocarcinoma/metastatic carcinoma were reviewed and correlated with their performance in the program.
The CAP Nongynecologic Cytology Program is a quarterly mailed, glass slide quality improvement program. Cytology laboratories of all types participate, with the largest number (approximately 60%) being hospital laboratories. In addition, independent laboratories, federal and government laboratories, university laboratories, and others such as those associated with a group practice or physician's office also are in the participant base.
Slides are submitted by the members of the CAP Nongynecologic Cytology Working Group, which is a subcommittee of the CAP Cytopathology Resource Committee. All types of nongynecologic cytology sites are included in the program. Slides are reviewed by at least 2 experienced cytopathologists from the CAP Cytopathology Resource Committee before acceptance into the program. Each slide must be judged to be of good technical quality and an excellent example of the reference diagnosis. Both reviewers must agree on the exact target diagnosis, and this diagnosis must agree with the submitted diagnosis prior to accepting a slide for circulation.
Liver fine-needle aspirates with a reference diagnosis of adenocarcinoma/metastatic carcinoma were identified, and the performance of individual slides was tabulated. These cases were retrieved and reviewed by 2 of the authors (A.A.R. and T.R.M.) to identify potential cytologie features that could be responsible for the hepatocellular carcinoma responses.
Statistical analysis of categorical data was performed using a 2-tailed Fisher exact test or χ^sup 2^ test, as appropriate. P
A total of 1712 individual interpretations from 33 different cases of adenocarcinoma/metastatic carcinoma tumor in liver fine-needle aspiration specimens were reviewed. Overall, cases that were frequently misclassified as hepatocellular carcinoma were misclassified 26% of the time (range, 13%-54%). cases that were rarely misclassified, on the other hand, were less likely to be classified as hepatocellular carcinoma, recording on average only 0.7% of the time (range, 0%-3%; P
On review, cases that were frequently misclassified most often had moderate amounts of granular cytoplasm (16/ 16 cases) and round nuclei with even chromatin (13/16 cases; Figure 1, a through d). Trabeculae (3/16 cases), bare nuclei (2/16 cases; Figure 2, a and b), and endothelial wrapping (1/16 cases; Figure 3) were rarely present. In contrast, cases that were rarely misclassified had at least some areas with cells showing scant amounts of cytoplasm, which were crowded and overlapped or molded (13/17 cases) and which contained dark hyperchromatic chromatin (13/17 cases; Figure 4, a through c and Figure 5, a and b). These cytoplasmic and nuclear characteristics were statistically significantly different than those seen in cases that were frequently misclassified (P
The CAP Nongynecologic Cytology Program provides a unique opportunity to correlate the cytologie features of individual cases of a particular diagnosis with the interpretive opinions of numerous cytologists with a broad range of backgrounds and in a wide variety of practice settings, which may reflect the performance of a cross section of cytologists nationally. The results of this program are unique, and there are no results available from similar programs of comparable size.
The cytologie features of adenocarcinoma/metastatic carcinoma tumors in aspiration specimens of the liver are well known1,2 and in general are different than those that have been described for hepatocellular carcinoma.1,14 While it is commonly recognized that some poorly differentiated hepatocellular carcinomas may be difficult to distinguish from adenocarcinoma,1,2,5,9,12 difficulty in distinguishing cases of adenocarcinoma/metastatic carcinoma from hepatocellular carcinoma has not been as well described.
On review, it appeared that cases that were more likely to be misclassified had cytologie features distinct from cases that performed well, and consisted of cells with moderate amounts of granular cytoplasm and round nuclei with even chromatin. Such features are also typical of both normal and neoplastic hepatocytes, and it appears that participants may be using these features to suggest a diagnosis of hepatocellular carcinoma, rather than more specific features, such as broad trabeculae, bare nuclei, or endothelial cell wrapping. In support of this conclusion, cases that performed well almost always had areas that lacked this type of cytoplasm, and as a result the cells were crowded together, with either overlapping or nuclear molding. In addition, the nuclear chromatin was more often more dark and granular, a feature that is less common in hepatocytes, either normal or neoplastic.
These results highlight a very important problem in making the distinction between hepatocellular carcinoma and adenocarcinoma. While cases of hepatocellular carcinoma that show specific features, such as cellular trabeculae, are relatively easy to recognize, there are some cases of hepatocellular carcinoma that lack such specific features. In cases such as these, the present study results suggest that participants may rely too greatly on cytologie similarities of the cells with hepatocytes,2 while ignoring more typical features indicative of a nonhepatic origin. Additional educational efforts to increase participants' abilities to recognize subtle distinctions between these 2 tumors may be of benefit. In the context of this program, in which additional clinical history and special studies are not available, participants must rely strongly on fine cytologie details to make these often difficult, but clinically important distinctions. In actual clinical practice, both immunohistochemical studies and use of core needle biopsy would most likely help reduce this type of error. However, honing one's interpretive ability on the basis of cytology alone will ultimately lead to more accurate and cost-effective overall practice.
In conclusion, in the CAP Comparison Program in Nongynecologic Cytology, a surprisingly large number of cases of adenocarcinoma/metastatic carcinoma are being misclassified as hepatocellular carcinoma based on the presence of moderately abundant granular cytoplasm and round nuclei with even chromatin, features that mimic hepatocellular differentiation. Such cytologie kinship with hepatocytes should not be interpreted as sufficient for a diagnosis of hepatocellular carcinoma. Awareness of this cytologie overlap, increased educational efforts to improve participants' abilities to make this distinction, liberal use of cell blocks and core needle biopsies as well as histochemistry and immunohistochemistry (mucicarmine, HepPar, CDlO, carcinoembryonic antigen, CK20, and 34βE12), and use of additional clinical or laboratory information (such as serum α-fetoprotein) should improve cytologie practice when faced with this important differential diagnosis on fine-needle aspiration biopsy.
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Andrew A. Renshaw, MD; Jennifer HaJa, CT(ASCP); David C. Wilbur, MD; Theodore R. Miller, MD; for the Cytology Committee, College of American Pathologists
Accepted for publication June 6, 2005.
From the Department of Pathology, Baptist Hospital of Miami, Miami, FIa (Dr Renshaw); College of American Pathologists, Northfield, III (Ms HaJa); Department of Pathology, Massachusetts General Hospital, Boston (Dr Wilbur); and Department of Pathology, University of California Medical Center, San Francisco (Dr Miller).
The authors have no relevant financial interest in the products or companies described in this article.
Reprints: Andrew Renshaw, MD, Department of Pathology, Baptist Hospital of Miami, 8900 N Kendall Dr, Miami, FL 33156 (e-mail: firstname.lastname@example.org).
Copyright College of American Pathologists Oct 2005
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