Download Number 3 - Laboratory Animal Boards Study Group

Comparative Medicine
Volume 58, Number 3, June 2008
OVERVIEWS
Pacharinsk and Beitz. Animal Models of Cancer Pain, pp. 220-233
Domain 2: Management of Pain and Distress
Domain 3: Research, Task 3, Design and Conduct Research
SUMMARY:
 Animal models of cancer pain can be divided into 5 categories: bone cancer pain models,
non-bone cancer pain models, cancer invasion pain models, cancer chemotherapeutic-induced
peripheral neuropathy models, and spontaneous occurring cancer pain models.
 The most commonly used animal models of cancer pain have been developed in rodents
 Cancer pain is generated and maintained by a combination of the following mechanisms:
compression of bone, soft tissue, or peripheral nerve; vascular occlusion; and/or tumor
infiltration
 Cancer cells, inflammatory cells, and vascular cells release a variety of products, including
prostaglandins, ATP, bradykinin, cytokines, chemokines, nerve growth factor, and several
vascular factors that either excite or sensitize the nociceptor.
 Two common behavioral tests to quantify pain in rats and mice are the radiant heat
paw-withdrawal test and the von Frey test
QUESTIONS:
1. Nocifensive behaviors are described as
a. An increased response to noxious stimuli
b. An increased response to non-noxious stimuli
c. Vocalization and guarding of the affected limb
d. A response to non-noxious mechanical stimuli, such as palpation
2. In regards to its opioid receptor action, morphine is classified as
___________.
3. Explain the usefulness of the von Frey test.
4. Define intrathecal administration.
________ receptor
ANSWERS:
1. c
2. Mu; agonist
3. In the von Frey test, filaments of various thicknesses are applied against the central edge of the
animal's hind paw. Paw withdrawal caused by stimulation is registered as a response. The
von Frey device is used to produce a mechanical nociceptive stimulus for evaluation of the
antinociceptive effects of various compounds.
4. Through the theca of the spinal cord into the subarachnoid space
Ray et al. Fatigue and Sleep during Cancer and Chemotherapy: Translational Rodent
Models, pp. 234-245
Primary Species - Mouse
SUMMARY: The frequent occurrence of fatigue and disturbed sleep in cancer survivors and the
negative effect of these symptoms on quality of life underscore the need to identify mechanisms
that cause cancer-related fatigue, with a view toward developing more effective treatments for this
problem. Animal studies are easier to control and standardize than studies on people and are
crucial to the identification and understanding of underlying disease mechanisms. This review
describes the need for, the feasibility of, and several possible approaches to measure fatigue in
animal models of cancer.
QUESTIONS
1. What are the four physical changes related with fatigue described by cancer patients?
2. Cancer related fatigue is:
a. A subjective report of tiredness
b. Persistent and extend in duration
c. Severe enough to cause distress
d. All of above
3. T/F Fatigue is common in many types of malignancies and is reported to occur after therapy
4. Cancer and its treatments have the capacity to cause fatigue via affecting:
a. Metabolism
b. Hormonal system
c. Asleep
d. a and c are correct
5. T/F circadian rhythms influence cancer development and treatment through the activity of
so-called “clock genes” which modulate the timing and progression of the cell cycle, cell division
and apoptosis
6. Fatigue and sleep alterations can produce in cancer patients:
a. Decreased quality of life
b. Reduced compliance with treatment
c. Poor prognosis
d. All of above
7. Between cancer initiation and chronic inflammation:
a. No relationship is assumed
b. Strong correlation is suspected
c. Substantial evidence support a casual link
d. Relationship has demonstrated only in human patients
8. In tumors with inflammatory cells infiltrates, what is the role of cytokines and chemokines?
9. Name 6 advantages of inbred strains of mice to study cancer
10. T/F Behavioral assessments in animals constitute a vital supplement to objective measurable
signs of illness
11. What of the next are examples of “sickness behavior” ?
a. Anhedonia, polyphagia
b. Hyperactivity, anorexia
c. Bulimia, increased social interaction
d. Fatigue, reduced social interaction
12. T/F prolonged production of high levels of sleep-promoting cytokines may cause fatigue
associated with chronic illness
13. Approach to fatigue in animals includes:
a. Spontaneous activity
b. Motivated behavior
c. Forced activity
d. All of above
14. The most commonly used method of forced activity is:
a. press a bar to obtain food
b. Running wheel
c. Avoid an aversive stimulus
d. Swimming pool
15. What is included on horizontal locomotion in mice to measure fatigue?
16. T/F horizontal locomotion in mice can be viewed as largely obligatory and to some degree
essential for life
17. What are the advantages to compare running wheel activity and normal locomotion of mice in
cages?
a. Level of polysomnography in each mouse
b. Simplicity and spontaneity of behavior
c. Exact measurement of fatigue
d. None of above
18. T/F mice with fatigue may reduce running wheel activity but not locomotor activity, providing an
objective measure
19. To differentiate muscle strength, motor impairment and post-exertional fatigue there is a model
that uses:
a. Timed swimming test and assessment of post swimming grooming and rearing
b. Timed wheel running and swimming test
c. Monitoring motivated behavior against finishing aversive stimulus
d. Horizontal locomotor and timed swimming test
20. Behavioral activity and sleep can:
a. Reflect fatigue
b. Contribute to fatigue
c. Exacerbate fatigue
d. a and b are correct
21. T/F C57BL/6 and BALB/CByJ mice show reduced activity in dark phase after inoculation with
influenza virus, and BALB /C also develop increased sleep in dark phase
22. Subjective non invasive assessment of fatigue in rodents induces reduced _____________
_________ and ___________ _ ________?
23. T/F Although Lewis lung carcinoma and etoposide (chemotherapeutic drug) increased levels of
IL6, anorexia is only related with drug administration in rodents
24. T/F Administration of chemotherapeutic agent etoposide reduced voluntary wheel running only
in tumor-bearing mice
25. T/F Taxanes (chemotherapeutic drug) have a side effect of peripheral neuropathy that may
mask or mimic fatigue
26. Which of the next behavioral markers should be evaluated to differentiate fatigue from
neurologic impairment in mice?
a. Open field activity, wire hang
b. Balance beam, inverted screen
c. Vertical pool
d. All
27. T/F All mice strains are deficient in production of melatonin, except C57BL/6 and BALB/C
28. T/F Due to variability in melatonin production, choosing the appropriate mouse strain is
essential to study the potential role of melatonin in controlling cancer in mice
29. Open field activity includes the measurement of what 4 things?
30. T/F The utility of a specific animal model is influenced directly by how closely it reproduces the
human disease
31. What are the four groups of mouse models of cancer?
32. Engrafted mouse models for cancer studies can be divided in ___________, ___________ and
__________?
33. The implantation of tumor cells into immunocompetent recipients of the same genetic
background is called:
a. Engrafted model
b. Clinical induced model
c. Histopathological model
d. Syngeneic model
34. Performing xenografts models is most commonly accomplished using mouse that bears
__________ or _________ mutation because………….?
35. The difference between nude and scid mice related to T cells and bone marrow is:
36. T/F The immunocompromised mice have normal or even increase innate immune responses
37. The advantages of engrafted mice models are (list 4 advantages):
38. T/F The phenotypes of implanted cell lines in mice reproduce accurately the phenotype of the
original tumor
39. T/F Normal immunocompetent mice reproduce accurately the normal host reaction to a tumor
particularly if the tumor is implanted orthotopically
40. T/F Most genetically engineered mouse models are less representative of human cancer
predisposition syndromes rather than random tumorigenesis
41. Genetically engineered models of mouse develop metastases in:
a. Few percentage and with different tissue specificity
b. High percentage and with same tissue specificity
c. Few percentage and with same tissue specificity
d. High percentage and with different tissue specificity
ANSWERS
1. Decreased physical performance; unusual or extreme tiredness; feelings of weakness; unusual
need for rest
2. d
3. F
4. c
5. T
6. d
7. c
8. Cytokines orchestrate communication between tumor cells, stromal cells and tumor infiltrating
immune cells whereas chemokines coordinate trafficking of immune cells into areas of
inflammation
9. Well defined and reproducible genetics; can be maintained in identically environments; can be
exposed to challenges at defined doses and ages; can be subjected to standardized
treatments; can undergo euthanasia for sample collection of time of interest; the large variety of
genetically defined strains provides a subrogate of human genetics diversity
10. T
11. d
12. F
13. d
14. b
15. The activity necessary for essential maintenance behavior such is feeding, drinking and
grooming
16. T
17. b
18. T
19. a
20. d
21. F
22. Spontaneous activity, response to manipulation
23. T
24. F
25. T
26. d
27. F
28. T
29. Pattern of exploration; amount of horizontal activity; amount of rearing; patterns of change with
time
30. T
31. Spontaneous, engrafted, pathogen-induced, chemically induced
32. Syngeneic, allogeneic, xenogeneic
33. d
34. Nude, scid; They rely on grafting a tumor cell line from one species onto a different recipient
species
35. T cells: nude mice have reduced lymphocyte population whereas SCID mice have absence of
mature cells
Bone marrow: nude mice have reduced bone marrow stem cells whereas SCID mice have
normal number of bone marrow cells
36. T
37. Experimental reproducibility; precise known onset of tumor formation; rapid tumor development;
easy tumor visualization
38. F
39. T
40. F
41. a
ORIGINAL RESEARCH
Mouse Models
Rehg and Sundberg. Utility of AntiPax5 in the Diagnosis of Lymphoproliferative Disorders
and Neoplasia in Mice, pp. 246-252
Primary Species - Mouse
Task 9 & 10
SUMMARY: This was an article from a Comparative Medicine journal edition dedicated entirely to
cancer research. B220 antigen has been historically used in paraffin embedded tissues as a
common panB-cell marker to assist in diagnosis of lymphoproliferative disorders and
lymphoma. The B220 antigen has shown limited specificity for this use due to the fact that it is also
expressed on cells other than B-cells, such as T-lymphocytes and plasmacytic dendritic cells, not
specific for the desired B-cell neoplasia diagnosis. This study focused on the use of the Pax5
protein which plays a central role in B-lymphocyte development and differentiation. Through
access to archived tissues from mouse lymphoid and non-lymphoid organs from necropsies of
transgenic mice that develop lymphoproliferative disorder, the authors compared the utility of the
Pax5 protein versus the B220 antigen in diagnostic pathology. Immunohistochemistry analysis of
these tissues showed how accurately different lymphoproliferations and lymphomas could be
identified with these markers and what other cells were also included with the markers (how
specific these were). The results confirmed the superiority of the Pax5 protein to the B220 antigen
for confirming the lineage of certain B-cell lymphomas and B-cell lymphoproliferative disorders and
aiding in a pathological diagnosis.
QUESTION:
1. Is the B220 antigen the best choice for pathological diagnosis of B-cell lymphoma? If not, what
would work better?
ANSWER
1. No. Pax5 protein, a B-cell-specific activator protein.
Huang et al. Histopathologic Findings and Establishment of Novel Tumor Lines from
Spontaneous Tumors in FVB/N Mice, pp. 253-263
SUMMARY: The inbred FVB mouse strain is used extensively in cancer research. Since little is
known about the incidence and characteristics of spontaneous tumors in these mice, the goal of the
study was to initiate a database of spontaneous tumors in retired FVB/N breeders, analyze the
histopathologic characteristics of these tumors, and establish novel tumor lines in vivo and in vitro.
In this study FVB/N breeders were used for spontaneous tumor studies and 6-8 wk old male and
female FVB/N wild-type and 2 other FVB transgenics were used for tumor transplantation. One
mammary adenocarcinoma and 1 lung alveolar-bronchial adenocarcinoma tumor were successfully
transplanted subcutaneously.
QUESTIONS:
1. Why is the FVB strain of mice used extensively for transgenic technology?
2. What was the most common neoplasm of both male and female retired FVB/N breeders ?
3. What was the second most common spontaneous tumor found in FVB/N female mice?
ANSWERS:
1. The FVB strain is used extensively for transgenic technology because of the prominent
pronuclei of its fertilized zygotes; this characteristic facilitates microinjection of foreign DNA.
2. The most common neoplasm in FVB/N breeders were alveolar-bronchial tumors of the lungs.
3. Mammary gland tumors
Girit et al. A Structured Light-based System for Scanning Subcutaneous Tumors in
Laboratory Animals, pp. 264-270
Task 1 – Prevent, Diagnose, Control and Treat Disease
Primary Species: Mouse
SUMMARY: A light based system for scanning subcutaneous tumors in female BALB/c athymic
nude (nu/nu) mice is being used to evaluate tumor volume as an endpoint in pre-clinical efficacy
studies of anticancer drugs. Despite the decreased cancer death rate due to early detection, there
is still an urgent need for improved treatment modalities. Methods currently in use for the
determination of tumor volume from 3-dimensional (3D) images from multi-slice data include:
computed axial tomography, positron emission tomography, single-photon emission computed
tomography and magnetic resonance imaging. However, these devices are too large for use in an
animal holding room and their use requires extensive preparation efforts, expensive materials, and
may be too impractical for high-throughput animal testing facilities.
The caliper technique is the most commonly used method for tumor measurement, but it is the least
accurate because there are several sources of error embedded in the measurement process itself:
inadequate formulas; inconsistent measurement of tumor axes, differences between investigators
who are taking the measurements; and the difficulty associated with measuring small tumors. To
add to the confusion, there are approximately 19 different formulae which can be used to measure
tumor volume. Tumor shape also deviates at different time points in the tumor growth phase and
presents difficulty with accuracy of volume measurements.
The optical scanning method described is felt to be in the running because it allows visual
comparison of tumors at their different stages of development, requires no anesthesia or contrast
agents, and can be automated with input of data into computer databases to enable automated
statistical analysis. In short, it integrates a wide range of the components necessary to bring
treatment modalities to the clinical stages at a faster pace. With this measurement technique,
tumor phantoms were made from sculptors clay and models used to assist in making the
comparison between volume measuring techniques.
The laser scanning technique was compared with those methods using a plethysmometer and the
standard caliper technique. Both laser scanning and plethysmometer were near perfect. Caliper
measurements tended to overestimate tumor volume, whereby measurement bias was
considerably reduced using the scanner method; it also yielded less variability across operator
differences. Positioning and animal alignment, shadowing effect and animal motion may adversely
affect scanning. Also, scanning will not allow measurement of the volume of any part of the tumor
below the plane of the surrounding healthy skin, but this should only be a concern for tumors larger
than 2.5 cm³. Laser scanning does have limitations, however it is a step forward in improving
methodology for small animal, pre clinical cancer-efficacy studies.
QUESTIONS:
1. Which of the following tumor size measurement techniques does NOT require the use of
anesthesia?
a. Magnetic resonance imaging
b. Ultrasonography
c. Microcomputed axial tomography
d. Caliper
e. Micro positron emission tomography
2. Which of the following techniques is the ‘gold standard’ method of tumor characterization?
a. Plethysmometry
b. Caliper
c. Physical mask
d. Tumor phantom
3. How much error in volume measurements is introduced when there is uncertainty regarding
tumor shape?
a. 10%
b. 25%
c. 27%
d. 15%
ANWERS:
1. D
2. A
3. B
Gades et al. Spontaneous Vulvar Papillomas in a Colony of Mice Used for Pancreatic
Cancer Research, pp. 271-275
SUMMARY: A colony of mice presented with vulvar masses. A census and examination
of colony animals was conducted, and line, gender, and mass location was recorded;
and a slide caliper was used to measure the width, length, and height of each
mass. The volume of each mass was then calculated.
The colony was composed of 2 lines, B6.FVB-Tg(Ipf1-cre)1Tuv and
B6;129-Kras2tm4Tyj, which were being crossbred to produce mice for a pancreatic
cancer study. The evaluations indicate that only mice resulting from the crossbreeding
of these two lines developed the masses. Of the 17 female mice, 7 were affected with
a vulvar mass (41.2% prevalence), and 1 unilateral and 1 bilateral periauricular mass
were also noted. The colony was evaluated a year later, and 11 of the 13 (84.6%) mice
evaluated had vulvar masses.
Histologic evaluation noted that the masses were papillomas. Papillomas are a benign
epithelial neoplasm consisting of villous or arborescent outgrowths of fibrovascular
stroma covered by neoplastic cells. Mice are infected by viruses in the Papovaviradae
family, but papillomas have not been reported in infected mice. The authors
hypothesize that these genetically engineered mice may have an altered phenotype
which may have resulted in the expression of the vulvular papillomas. Although,
diagnostic evaluation failed to reveal a viral etiology.
Excluding viral etiology, the authors feel that the most likely cause of the vulvar
papillomas is genetic. Molecular data confirmed activation of the Kras oncogene in the
vulvar tissue.
They propose that the interaction between the genetic background of
the mice and the introduced Kras oncogene may be responsible for the papillomas.
QUESTIONS:
1. Name a common animal model used to study human papillomaviral disease.
2. T or F. Vulvar masses are a common finding in mice?
3. The most common infectious cause of papillomas in most species is ______?
ANSWERS:
1. Rabbits
2. False, a search of the Mouse Tumor Biology Database revealed only 3 references.
3. Viruses
Zhou et al. Magnetic Resonance Imaging of the Response of a Mouse Model of Non-Small
Cell Lung Cancer to Tyrosine Kinase Inhibitor Treatment, pp. 276-281
Primary species: Mus musculus
Task 10. Design and conduct research
SUMMARY: Epidermal growth factor receptor (EGFR), a tyrosine kinas receptor, is linked to cell
growth in non-small cell lung cancers (NSCLC) through various mechanisms. The most common
mechanism is a mutational deletion of the extracellular domain of EGFR leading to a proliferative
advantage for the cells carrying this mutation.
The most common deletion variant, referred to as EGFRVIII, is a potential therapeutic target when
treating NSCLC with either antiEGFR antibodies or small-molecule EGFR tyrosine Kinase inhibitors
(for example erlotinib).
Magnetic resonance imaging (MRI) has and can be effectively used to image tumors. MRI of lungs
presents some unique imaging complications. 80% of the lung is air which has a very different
magnetic susceptibility than the surrounding lung tissue, resulting in low signal intensity. The use
of hyperpolarized gas (He and Xe) can assist with lung imaging but this only resolves areas where
the gas can be distributed. Another complication of imaging the chest is the motion related to
respiration and the beating heart. To a large extent this complication can be offset by gating. In
this study tumor MRI was used to evaluate tumorigenesis, maintenance and tumor response to
treatment with erlotinib. A tetracycline-inducible expression of EGFRvIII model was used to
generate the NSCLC.
Histology revealed adenomatous hyperplasia, adenomas and adenocarcinomas after 8, 12 and 16
weeks respectively in the transgenic mice over expressing EGFRvIII while drinking the
doxycycline. When the doxycycline was removed the tumors regressed and did not re-grow
indicating that tumor maintenance depends on the continued expression of EGFRvIII. 14 days of
therapy with erlotinib, in mice drinking doxycycline, reduced tumor volumes by an average of 85.4%
QUESTIONS:
1. What is the most common variant of epidermal growth factor that leads to non-small cell lung
cancer?
2. List 2 complications that effect generating good images when trying to do MRI of the chest.
3. What is one solution to offset the magnetic susceptibility difference between air and the
surrounding lung tissue?
ANSWERS:
1. EGFRVIII
2. a) the magnetic susceptibility difference between air and the surrounding lung tissue and b)
motion associated with respiration and the beating heart.
3. The use of hyperpolarized gases such as He and Xe
Rat Model
Kamocka et al. Rat Prostate Tumors Express Cancer Procoagulant, an Activator of
Coagulation Factor X, pp. 282-286
SUMMARY: Two activators, tissue factor and cancer procoagulant (CP), are associated with a
tumor’s ability to cause thrombotic complications throughout the body. Both are known to be
present in increased concentrations within cancerous tissue of various tumor types. The
thrombotic ability of the tumor works by , in the case of tissue factor, initiating the extrinsic pathway
of coagulation, and in the case of CP, by activating coagulation factor X.
A spontaneous prostate tumor of the Lobund-Wistar rat (LW) has similarities with human prostate
tumors. These similarities include androgen modulated growth, age-dependent spontaneous
onset, metastatic potential, and the fact that the tumors develop on the anterior, dorsal, and lateral
lobes of the prostate, just like humans. Previous publications had reported the presence of tissue
factor on these tumors, but none had reported the presence of CP. After inoculating prostate
tumors into the flanks of LW rats, the tumors were harvested, extracted, and then purified by
ion-exchange chromatography. CP activity in the samples was determined by a 3-stage
chromogenic assay. Presence and activity was detected in the tumors, but not in healthy tissue
that was harvested from around the tumor and used for a comparison. This confirmed the
increased presence of CP in the LW rat prostate tumors.
It has been shown in several different tumor lines that inhibition of tissue factor activity limited and
sometimes eliminated the metastatic effects of these tumors. CP is not as well know and studied
because the genomic sequence is unknown and no cDNA sequence is available, so manipulating
CP expression to explore function has been difficult. With the demonstration of the presence of CP
within the LW rat prostate tumor, this model has the potential to be used for further study of CP and
its physiologic role.
QUESTIONS:
1. What are two factors involved in a tumor’s ability to cause thrombosis throughout the body?
2. What are 4 essential characteristics of an animal model of prostate cancer necessary to mimic
prostate cancer of a human?
ANSWERS:
1. Tissue Factor and Cancer Procoagulant
2. Androgen modulated growth, age-dependent spontaneous onset, metastatic potential, and
cancer development on the anterior, dorsal, and lateral lobes of the prostate. Other common
cancer models in animals have only developed prostatic cancer on the ventral lobe.
Rabbit Model
Kreuter et al. Development of a Rabbit Pleural Cancer Model by Using VX2 Tumors, pp.
287-293
Task 9 - Collaborate on the Selection and Development of Animal Models
K1 Animal models (spontaneous and induced)
Species: Tertiary- New Zealand white rabbits (Orycytolagus cuniculis)
SUMMARY: There has been a need to develop a reproducible model of pleural cancer
in a moderate-size immunocompetent animal. Previously, small murine animal models
have been difficult to evaluate imaging and treatment modalities because their pleural
space is not comparable to that of humans. This study evaluated 4 different tumor
induction methods using pathogen-free male New Zealand white rabbits (Orycytolagus
cuniculis). The first evaluated pleural tumor inoculation where VX2 tumor cells were
injected into the pleural space. All 14 rabbits, 9 which received previously frozen cells
and 5 which received fresh tumor cells, developed pleural tumors by 24 days
post-inoculation. Pleural tumor then metastasized to the chest wall, visceral lung
surfaces, ribs and the diaphragm. The second injection approach, intramuscular
inoculation, developed a localized, muscular, thigh mass that eventually spread to the
lung parenchyma. The intravenous injection resulted in lung parenchymal tumors. The
fourth type of injection, a direct lung parenchymal injection, was preceded with abrading
the parietal pleura gently with the end of a sterile cotton-tip applicator. This was done
so that the tumor cells could adhere. This type of injection did result in lung
parenchymal tumor development. Overall, this study demonstrated a pleural cancer
model in moderate-sized immunocompetent animals that can be used to evaluate
cancer development and treatment modalities.
QUESTIONS:
1. T or F: In cancer research, primary fresh tumor cells vs. frozen cells are generally
preferred for implantation because of their consistent and rapid growth.
2. Which modality enables direct visualization of pleural effusions which are indicative
of pleural malignancy?
A. Ultrasound
B. Radiography
C. MRI
D. CT
3. T or F: Characteristics of neoplastic cells include high nuclear: cytoplasmic ratio,
high mitotic activity, and many nucleoli.
ANSWERS:
1. T
2. B
3. T
CASE STUDIES
Kondo et al. Spontaneous Fibrosarcoma in a Djungarian Hamster (Phodopus sungorus),
pp. 294-296
Domain 1, Task 3: Diagnose disease or condition as appropriate
Tertiary Species: Other rodents
SUMMARY: A 1.5 year old Djungarian, female, 77.8 g pet hamster was presented with a large (25
g, 32% of total body weight) SQ mass. The mass had first been noticed 3 mo. earlier by the owner.
At time of presentation mass was encompassing entire right shoulder and interfering with
ambulation. Radiographic findings included dislocation of right humeral articulation and osteolytic
lesion of scapula. The hamster died one week after presentation and was submitted for
necropsy. Diagnosis was made using histological and immunonohistochemical methods.
Histologically; neoplastic cells had invaded bone, skeletal m., and SQ tissues.
Immunohistochemisty; >90% of cells stained positive for vimentin, but were negative for S100
protein, neurofilament, and desmin. Additionally, 10-20% of neoplastic cells were positive for SMA.
This is the first occurrence in the literature of a spontaneous fibrosarcoma in a Djungarian hamster.
QUESTIONS:
1. In this case positive intracytoplasmic staining for Vimentin points to what cell type?
2. Why did the authors accept a diagnosis of myofibroblastic sarcoma?
3. What does anti-SMA stain for?
ANSWERS:
1. Fibroblasts
2. Because 10-20% of the neoplastic cells stained positive for SMA.
3. Smooth muscle actin.
Sikoski et al. Cystic Mammary Adenocarcinoma Associated with a Prolactin-secreting
Pituitary Adenoma in a New Zealand White Rabbit (Oryctolagus cuniculus), pp. 297-300
Domain 1: Management of Spontaneous and Experimentally Induced Diseases and Conditions
Primary Species - Rabbit
SUMMARY: This article is a case report describing a rabbit that presented with a cystic mammary
adenocarcinoma. The rabbit was a 44 month old nulliparous NZW. Clinical signs on presentation
included bilateral enlargement of the mammary glands with a watery brown fluid discharge. Small
firm masses were palpable within some of the glands and several teats were mildly enlarged and
had mucoid discharge. Initial diagnostics included a CBC, chemistry and culture of the exudates. A
presumptive diagnosis of mastitis was made and the rabbit was started on enrofloxacin at 5 mg/kg
IM once daily for 10 days and ketoprofen at 3 mg/kg IM as needed. The CBC and chemistry results
were within normal limits and the exudate culture was negative. After the clinical symptoms did not
resolve, a diagnosis of mammary dysplasia secondary to a prolactin secreting tumor was
considered. Computed Tomography (CT) was performed on the affected rabbit and an age
matched clinically normal rabbit. The scan of the affected rabbit revealed an irregularly shaped
pituitary gland approximately 3 to 5 times larger than that of the normal rabbit. Serum prolactin
measurements were done on both the normal and affected rabbits. The prolactin level of the
affected rabbit was 19.2 ng/mL vs. normal ranges reported within 2.7 – 4.0 ng/mL.
The affected rabbit was on a long term urogenital tissue autograft study and was euthanized at a
planned endpoint and a full diagnostic necropsy was performed. Gross findings included enlarged
pituitary and mammary glands with the latter having brown exudate. Histological analysis of the
pituitary revealed a pituitary adenoma and immunohistochemical staining showed the presence of
prolactin supporting the diagnosis of a prolactin secreting pituitary adenoma with secondary
mammary dysplasia. Histology on the mammary glands revealed hyperplasia and dysplasia with
progression to mammary adenocarcinoma in some areas.
Prolactin secreting pituitary tumors with mammary dysplasia were previously reported in NZW
rabbits as well as FVB/NCr mice. This is the first report of mammary dysplasia progressing to
mammary adenocarcinoma in the presence of a prolactin secreting pituitary tumor but a similar
progression has been reported in humans. There is also evidence from the human literature that
hyperprolactinemia can lead to malignancy. The use of CT aided in the antemortem diagnosis of
the condition.
QUESTIONS:
1. True or False: This case report represents the first time a prolactin secreting pituitary tumor has
been reported in an NZW rabbit?
2. In what strain of mouse have prolactin secreting pituitary tumors with mammary dysplasia been
reported?
3. True or False: Hyperprolactinemia does not contribute to malignancy
ANSWERS:
1. False, there are previous reports of this condition – this is the first report of mammary dysplasia
progressing to mammary adenocarcinoma in the presence of a prolactin secreting pituitary
tumor
2. FVB/NCr
3. False, in addition to this case, there are reports in the human literature that malignancy can be
triggered by hyperprolactinemia