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NTP Holds Symposium on Pathology

By Mamta Behl
August 2010

NTP Pathologist Susan Elmore, D.V.M.
Elmore is a board-certified veterinary pathologist and staff scientist in the NTP Pathology Group. (Photo courtesy of Steve McCaw)

Pathologist Bob Maronpot, D.V.M.,
Maronpot is a board-certified veterinary pathologist and toxicologist who has designed, conducted, and evaluated animal carcinogenesis studies for 40 years, including 26 years at NIEHS/NTP. (Photo courtesy of Steve McCaw)

Several NIEHS pathologists participated in the 2010 joint symposium of the Society of Toxicologic Pathology (STP) and the International Federation of Societies of Toxicologic Pathologists (IFSTP) June 19-24 in Chicago. As part of the annual meeting, NTP sponsored a satellite session encompassing what organizers billed as a "Pathology Potpourri," featuring several noteworthy presentations as well as a talk on proposed International Harmonization of Nomenclature and Diagnostic (INHAND) Criteria for Lesions in Rats and Mice.( Exit NIEHS

The symposium chair, NTP Pathologist Susan Elmore, D.V.M., opened the session with a warm welcome. This interactive symposium has become a popular pre-meeting event for attendees of the annual STP symposium with the objective of providing continuing education on the fine points of interpreting pathology slides and generating lively and productive discussion of the challenges and pitfalls involved.

Striving for accurate identification and diagnosis

A longstanding debate in the field of pathology involves the ability to distinguish among different liver lesions. Rodney Miller, a pathologist with Experimental Pathology Laboratories, Inc., addressed this question in a talk titled "Rat and Mouse: Are They Really That Different?" Miller explored the issue in terms of liver lesions in different rodent species by displaying a set of case studies and then asking pathologists in the room to vote on the diagnosis.

Miller's talk compared and contrasted the diagnosis of several lesions such as hepatocholangiocarcinomas, hepatoblastomas, hepatocellular carcinomas, and hepatocholangiomas in rats and mice. Miller focused on specific diagnostic differences in hepatocholangiocarcinomas and metastatic lesions in F344/N rats and B6C3F1 mice.

Elmore followed with a talk that highlighted case studies on the identification of amorphous eosinophilic substances within the kidney and nasal septum, "What Is That Pink Eosinophilic Material?" Elmore presented a series of slides and asked pathologists to cast a vote on their diagnosis. Interestingly, "amyloid" topped the list as a diagnosis for the amorphous eosinophilic material, although Elmore subsequently presented a series of stained slides and electron microscopic images revealing the absence of amyloid. In Elmore's take home message, she said, "Not everything that is amorphous and eosinophilic should be diagnosed as amyloid." She left the pathologists with an important lesson about what she described as traditional "knee-jerk" diagnoses.

An introduction to INHAND criteria of central and peripheral nervous system (CNS/PNS) proliferative lesions by Alys Bradley, head of pathology for preclinical services at Charles River Laboratories - United Kingdom, provided an overview on the different INHAND terminologies. Bradley opened the talk by explaining the INHAND project and the role of the INHAND nervous system working group. She went on to discuss the identification and distinction between benign and malignant lesions in the nervous system, such as ependymomas, medulloblastomas, papillomas, schwannomas, and astrocymas, and concluded her talk by providing the audience a plethora of well-defined information on the characterization of CNS/PNS lesions.

Concluding the agenda was pathologist Bob Maronpot, D.V.M., an independent consultant and retired NTP scientist, who highlighted the challenges associated with distinguishing cholangiofibrosis from cholangiocarcinoma. Cholangiocarcinoma is regarded as a neoplasm ( Exit NIEHS of the bile ducts ( Exit NIEHS, which drain bile ( Exit NIEHS from the liver ( Exit NIEHS into the small intestine ( Exit NIEHS, and is often difficult to distinguish histopathologically from its precursor cholangiofibrosis.

Maronpot presented slides with case studies of various bile duct lesions, such as cholangiomas, cystic cholangiomas, cholangiofibrosis, cystic cholangiofibrosis, and cholangiocarcinoma-intestinal type. He then asked pathologists in the room to cast their vote on a diagnosis. The attendees offered several thoughtful answers with different rationales for diagnosis.

After he explained the pathogenesis and potential mechanisms involved with formation of the lesions, Maronpot closed by reminding his audience about the need for careful consideration when it comes to diagnosis. "The challenge [here] is to be able to distinguish between cholangiofibrosis and cholangiocarcinoma," he said.

(Mamta Behl, Ph.D., is a research fellow in the NTP Toxicology Branch)

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