© The Author 2007. Published by Oxford University Press.
CORRESPONDENCE |
Response: Re: Impact of Classification of Hilar Cholangiocarcinomas (Klatskin Tumors) on Incidence of Intra- and Extrahepatic Cholangiocarcinoma in the United States
Affiliation of authors: Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD
Correspondence to: Tania M. Welzel, MD, MHS, Division of Cancer Epidemiology and Genetics, National Cancer Institute, 6120 Executive Blvd, EPS Ste 500, Rockville, MD 20892 (e-mail: tmwelzel{at}web.de).
We appreciate the interest of Matull et al. in our study of the impact of classification of hilar cholangiocarcinoma on rates of intra- and extrahepatic cholangiocarcinomas. We completely agree, as noted in our paper, that a consistent global classification of hilar cholangiocarcinoma is required to compare trends around the world. We do not concur, however, that hilar cholangiocarcinomas are ever properly classified as intrahepatic tumors. As defined by Klatskin in 1965 (1), hilar cholangiocarcinomas (also known as Klatskin tumors) occur at a specific location, the bifurcation of the common hepatic duct. Because the bifurcation of the common hepatic duct is extrahepatic, tumors that occur at this location are, by definition, extrahepatic tumors.
There is no doubt that hilar cholangiocarcinomas have often invaded the liver at the time of diagnosis as noted by Matull et al. This observation, however, does not support classifying hilar cholangiocarcinomas as intrahepatic tumors. Since the publication of the Sixth Revision of the International Statistical Classification of Diseases, Injuries, and Causes of Death in 1948, the coding of neoplasms has been based primarily on topographic site of origin, not on pattern of invasion (2). Although hilar cholangiocarcinomas can occasionally present as exophytic masses and, as such, can appear to be similar to intrahepatic lesions, primary intrahepatic disease can mostly be delineated from advanced hilar cholangiocarcinoma (Bismuth types III and IV) based on clinical presentation and diagnostic imaging (3,4, Sahani DV: personal communication).
As noted in our manuscript, we believe that additional confusion has been created by assigning a morphology (histology) code (8162/3, Klatskin) rather than a topography code to hilar cholangiocarcinomas in International Classification of Diseases for Oncology (ICD-O), 2nd and 3rd editions (2,5). Concerning the proportion of all cholangiocarcinomas that are hilar tumors, we advise caution in accepting the figure of two-thirds, as quoted by Matull et al. To the best of our knowledge, this estimate arose from a single study conducted among patients with histologically confirmed disease who underwent surgical exploration at a tertiary medical center in the United States (6). This patient population is unlikely to be representative of all patients with cholangiocarcinoma. The results of the study, however, were referenced in the review article cited by Matull et al. (7). As we noted in our manuscript, only 8% of cholangiocarcinoma in Surveillance, Epidemiology, and End Results were coded, as hilar cholangiocarcinomas, to Klatskin code 8162/3. This estimate is undoubtedly too low, for reasons we mentioned in our paper, but the estimate of two-thirds is almost certainly too high.
With this in mind, we suggested that hilar cholangiocarcinomas be assigned a separate topography code by the ICD-O, listed as a subsite of extrahepatic cholangiocarcinoma. An alternative would be to assign all cholangiocarcinomas (intrahepatic and extrahepatic) a single topography code and then assign the specific locations of the tumors in the bile duct to subcategories of that topography code.
In conclusion, we believe that having a well-accepted consistently applied classification for hilar cholangiocarcinoma would be of tremendous use to both the research and the clinical arenas. We agree that developing such a coding practice may be a large task but suggest that it is a task well-worth undertaking.
REFERENCES
(1) Klatskin G. (1965) Adenocarcinoma of the hepatic duct at its bifurcation within the porta hepatis. An unusual tumor with distinctive clinical and pathological features. Am J Med 38:241–56.[CrossRef][ISI][Medline]
(2) In Sobin LH and Parkin MD (Eds.). International classification of diseases for oncology (ICD-O) (2000) 3rd ed (World Health Organization, Geneva (Switzerland)).
(3) Slattery JM and Sahani DV. (2006) What is the current state of the art imaging for detection and staging of cholangiocarcinoma. Oncologist 11:913–22.
(4) Lazaridis KN and Gores GJ. (2005) Cholangiocarcinoma. Gastroenterology 128:1655–67.[CrossRef][ISI][Medline]
(5) Percy C, Van Holten V, Muir C. (1990) International classification of diseases for oncology (ICD-O) 2nd ed (World Health Organization, Geneva (Switzerland)).
(6) Nakeeb A, Pitt HA, Sohn TA, Coleman J, Abrams RA, Piantadosi S, et al. (1996) Cholangiocarcinoma: a spectrum of intrahepatic, perihilar, and distal tumors. Ann Surg 224:463–73.[CrossRef][ISI][Medline]
(7) de Groen PC, Gores GJ, LaRusso NF, Gunderson LL, Nagorney DM. (1999) Biliary tract cancers. N Engl J Med 341:1368–78.
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J Natl Cancer Inst 2007 99: 407.
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