|
The following questions, and sample answers, are derived from a "mock examination" provided at the University of Giessen in April 2001.
They are illustrative of the different styles used in the examinations but do not necessarily reflect the degree of severity of the actual membership examination.
This example is based on an idea from: American Journal of Pathology (2000) 157: 671-677
EXAMINATION NOTES - PLEASE READ CAREFULLY BEFORE STARTING THE EXAM!!
This section of the exam tests problem solving, data analysis, and interpretation skills by MULTIPLE PART questions. The format of the questions varies and histopathology slides, photomicrographs, data tables, tissue/cell analyses, and graphical data may be pesented. All of the information needed to answer the question is presented. It is expected that candidates should interpret and make critical judgements on the data given in order to answer the question correctly.
WITHIN EACH MAIN QUESTION, THE SUBSECTION QUESTIONS ARE NOT EQUALLY WEIGHTED, DO NOT ASSUME THAT EACH WiLL TAKE THE SAME AMOUNT OF TIME TO ANSWER.
PROBLEM # 2
Please read first all the questions before you answer!
Introduction
The oncogene onc is associated with the induction of neoplasia in a variety of endocrine organs in mice. Transgenic mice with targeted expression of this oncogene develop neoplasia in target organs. In order to study, whether the tumor suppressor gene neopun is important in the pathogenesis of these tumors, onc transgenic mice were cross-bred with neopun knock-out mice.
Question 2A: What is meant by: "targeted expression of an oncogene"?
Sample answer: The oncogene is under the control of a promoter which is tissue or organ specific. Therefore the protein of the oncogene is only expressed in these organs, increasing the frequence of neoplasia in these organs.
Question 2B: What is a "tumor suppressor knock-out mouse"?
Sample answer: In knock-out mice both alleles of the tumor suppressor gene are inactive or absent and no functional protein is produced.
Off-spring mice were genotyped by polymerase chain reaction (PCR) for the presence of the oncogene onc (O+) and absence of the tumor suppressor gene neopun (N-/-):
Table 1. Correlation of the histological findings and the PCR results.
PCR results |
O (-/-), N(+/+)
|
O(-/-), N(-/-)
|
O(+), N (+/-)
O(+), N (+/+)
|
O(+), N(-/-) |
Histology |
Figure 1
|
Data not shown
(target organ was not involved)
|
Figure 2
|
Figure 3
|
Question 2C: Discuss the PCR results of Table 1 (top row only).
Sample answer:
O(-/-) is absence of the oncogene (as in normal mice)
N(+/+) or N(+/-) is presence of both or one allele of the tumor suppressor gene respectively (as in
normal mice)
O(+) is presence of the oncogene, so oncogenic protein can be produced
N(-/-) is absence of both alleles of the tumor suppressor gene, therefore no protein can be produced
By 17 weeks of age many off-spring mice had developed tumors. Mice were grouped according to the histological appearance of the target organ. Figures 1 - 3 (prints in the provided slide map) show typical results of the different groups.
The figure on the left hand side (a) represents an overview and the figure on the right hand side (b) is a higher magnification.
Histology
Question 2D: Analyze the histological data of Figures 1 - 3 and give a morphological diagnosis.
Sample answer:
Figure 1 Morphological Diagnosis: Normal thyroid.
Figure 2 Morphological Diagnosis: Thyroid hyperplasia/ adenoma.
Figure 3 Morphological Diagnosis: Invasive thyroid carcinoma; important to recognize that 3 is a progression from 2.
Question 2E: Correlate the PCR results with your morphological diagnosis.
Sample answer:
Figure 1: normal tissue, absence of oncogene and presence of tumor suppressor gene, as it should be in a normal physiological situation.
Figure 2: presence of the oncogene in presence of one allele of the functional tumor suppressor gene results in induction of a thyroid tumor which is not invasive.
Figure 3: absence of any tumor suppressor gene product (as no allele is present) and presence of the oncogene results in the formation of at least locally invasive thyroid tumors.
Question 2F: Discuss your overall findings.
Sample answer:
Presence of the targeted oncogene results in tumor induction, however, for transformation into an locally invasive tumor, the absence of functional tumor suppressor gene protein is also required.That means that the presence of the tumor suppressor gene protects against invasiveness and possibly (not conclusive from submitted data) against metastatic disease.
Example questions from other sections of the ECVP examination:
This page was last updated
April 17, 2005
|
Veterinary Pathology
