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Israel Journal of Veterinary Medicine  Vol. 69 (2)  June 2014 Gardhouse, S. 102
CASE REPORT
A 6-year-old female intact captive raccoon (Procyon lo-
tor) housed at a local zoo was examined by the Exotics and
Zoological Medicine Service at Kansas State University for
an annual health examination. Te raccoon had been do-
ing well at the zoo and the keepers had no concerns at the
time of presentation. Te raccoon was fed omnivore biscuits
(Zupreem omnivore diet, Premium Nutritional Products
Inc., Shawnee, KS, USA), weight control dog food (Iams
ProActive Health Adult Weight Control, Proctor and
Gamble, Dayton, OH, USA), apples, bananas and grapes as
the main staples; feline diet (Nebraska Brand Classic Feline
Diet, Central Nebraska Packing, Inc., North Platte, NE,
USA) and occasionally lake smelt rotated, as well as other
fruits and vegetables. Te raccoon was housed with two other
raccoons at the zoo that showed no signs of disease other
than being chronically overweight.
On presentation, the raccoon was bright, alert, and re-
sponsive. Te raccoon was hand injected with ketamine
hydrochloride (10 mg/kg intramuscularly, Ketalar, JHP
Tyroid Neoplasia in a Raccoon (Procyon lotor)
Gardhouse, S.,
1
* Eshar, D.,
1
Meindel, M.J.,
2
Nuth, E.
1
and Delk, K.
3
1
Departments of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA 66506.
2
Departments of Diagnostic Medicine / Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan,
KS, USA 66506.
3
Zoological Medicine Service, WR Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, CA,
USA 95616.
* Corresponding Author: Dr. Sara Gardhouse, Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, 1800 Denison
Avenue, Manhattan, KS 66506, USA. Tel: (785)-706-1276, Fax: (785)-532-4309. Email: sgardhou@vet.k-state.edu.
ABSTRACT
A 6 year-old female intact captive raccoon (Procyon lotor) was presented for a routine annual health
evaluation. On physical examination, the raccoon was obese and bilateral ventral cervical masses were
palpated. Complete blood count was within normal limits. Serum biochemistry profle revealed an increased
alkaline phosphatase activity, increased phosphorus and decreased chloride concentrations. Two-view whole
body radiographs were performed and revealed a ventral cervical well-circumscribed soft tissue opacity
extending to both sides of the midline, splenomegaly, and a pulmonary nodule. Abdominal ultrasound was
performed and was unremarkable. Ultrasonographic examination of the cervical region revealed bilateral
cervical soft tissue masses in the area of the thyroid glands. Ultrasound-guided fne needle aspirates of
the mass were suggestive of an epithelial neoplasm most likely of thyroid gland origin. When compared
to canine references, the total thyroxine values (tT4) and triiodothyronine (T3) values were increased on a
thyroid panel performed at Michigan State University. In house tT4 values were also increased, though more
signifcantly than those on outside testing. Given the lack of clinical symptoms related to the pathology, the
potential risks of a surgical thyroid procedure and the suspicion of pulmonary metastasis, further diagnostics
and treatment were declined. To date, 19 months from the time of the initial presentation, the raccoon is
doing clinically well with no obvious clinical signs other than the palpable prominent cervical masses.
Keywords: Tyroid adenoma, thyroid adenocarcinoma, hyperthyroidism, raccoon, Procyon lotor.
Israel Journal of Veterinary Medicine  Vol. 69 (2)  June 2014 103 Tyroid Neoplasia in a Raccoon
Pharmaceuticals LLC, Parsippany, NJ, USA) and medetomi-
dine (0.035 mg/kg intramuscularly, Domitor, Pfzer Animal
Health, Exton, PA, USA) for physical examination. Once
sedated, chamber induction of anesthesia was achieved with
isofurane (5%) in oxygen (2L/min). Te raccoon was intu-
bated with a 5.0 mm endotracheal tube and maintained un-
der anesthesia with isofurane (2%) in oxygen (2L/min). An
intravenous catheter was placed in the left lateral saphenous
vein and the raccoon was given Lactated Ringer’s Solution
(5 mL/kg/hour, B. Braun Medical Inc., Irvine, CA, USA).
On physical examination the raccoon was overweight
(11.2 kg) with a body condition score of 5 out of 5. Te rac-
coon had mild dental tartar, and two 4-6 cm diameter bilat-
eral ventral cervical masses were palpated. A blood sample
was obtained from the lateral saphenous vein and submitted
for a complete blood count (CBC) and biochemical profle.
Te results of the CBC were within normal reference limits
(1). Te results of the biochemistry profle showed a mild in-
crease in phosphorus of 0.47 mmol/L (reference range 0.17-
0.45 mmol/L); a mild decrease in chloride of 101 mmol/L
(reference range 103-117 mmol/L); and a mild increase in
alkaline phosphatase activity (ALP) of 171 U/L (reference
range 21-149 U/L) (1).
Te initial diferential diagnosis list for the cervical
masses included hyperplasia, neoplasia, abscess, or cyst with
organs of origin to include salivary gland, lymph node, or
thyroid gland. A fne needle aspirate (FNA) of the ventral
cervical mass yielded serosanguinous fuid. Following the
FNA, an abscess seemed less likely, given the appearance of
the fuid.
Two days later the raccoon was brought in for further
testing and was immobilized again using the previously de-
scribed anesthesia protocol. Two-view whole body radio-
graphs were performed and revealed a ventral cervical well
circumscribed soft tissue opacity extending to both sides
of midline measuring approximately 3.0 cm in diameter,
splenomegaly, and a pulmonary nodule, 0.8 cm in diameter
(Figure 1).
Figure 1: Left lateral cervical and thoracic radiograph of the raccoon.
Notice the ventral cervical soft tissue opacity (white arrow) and pulmonary nodule (black arrow).
Case Reports
Israel Journal of Veterinary Medicine  Vol. 69 (2)  June 2014 Gardhouse, S. 104
An abdominal ultrasonographic examination was per-
formed and was unremarkable. Cervical ultrasonography re-
vealed bilateral cervical soft tissue masses in the area of the
thyroid glands. Te mass on the right side was heterogeneous
and larger than the left, measuring 2.4 cm × 5.3 cm × 5.5 cm.
It contained a large anechoic fuid-flled cystic component
and a more solid component towards the caudal pole. Te left
sided mass measured 3 cm × 4.3 cm × 4.1 cm and was het-
erogeneous in echogenicity. Tere was extensive blood fow
identifed via Doppler within and in the periphery of both
masses; however, no large vessels were identifed to directly
invade the mass.
An ultrasound-guided FNA of both cervical masses was
performed and the recovered fuid was dark red in color,
suggestive of a strong presence of blood in the sample. Te
cytologic preparations demonstrated high nucleated cel-
lularities, numerous erythrocytes, and pale backgrounds.
Nucleated cells consisted primarily of clustered and indi-
vidualized round, oval, or basaloid epithelial cells with round
nuclei containing stippled chromatin patterns and small or
indistinct nucleoli (Figure 2). Tere were moderate amounts
of lightly basophilic cytoplasm that often contained variable
numbers of dark blue granules most consistent with tyrosine
granules. Cell borders were indistinct. Anisocytosis and an-
isokaryosis were minimal except in rare clusters of pleomor-
phic cells. Rare binucleated cells were identifed. Occasional
macrophages, including erythrophages and pigment-laden
macrophages most consistent with siderophages, and eo-
sinophils were also observed. Te cytologic diagnosis given
was epithelial neoplasm most likely of thyroid gland origin.
Te main diferential diagnoses following the FNA cytol-
ogy included a thyroid adenoma, or adenocarcinoma; how-
ever, hyperplastic thyroid glands could not be excluded as a
diferential.
Blood thyroid hormones concentrations were evaluated.
Te tT4 concentration performed at Kansas State University
demonstrated a tT4 of >309 ηmol/L (canine reference inter-
val: 10.0-45.5 ηmol/L) (Kansas State University, Diagnostic
Lab, KS, USA). A thyroid hormones panel performed at
Michigan State University revealed a tT4 >156 ηmol/L (ca-
nine reference interval: 11-60 ηmol/L), T3 > 4.7 ηmol/L
(canine reference interval: 0.8-2.1 ηmol/L), free thyroxine
concentration by equilibrium dialysis > 128 ρmol/L (canine
reference interval 6-23 ηmol/L), thyroid stimulation hor-
mone 6 mU/L (canine reference interval: 0-30 mU/L), thy-
roxine autoantibody 7% (canine reference interval: 0-20%),
triiodothyronine autoantibody 3% (canine reference interval:
0-10%), and thyroglobulin autoantibody was not detected (ca-
nine reference interval: 0-35%) (Michigan State University,
Diagnostic Center for Population and Animal Health, USA).
Tese results were highly suggestive of hyperthyroidism when
compared to canine reference intervals; however there are no
established reference intervals or background data regarding
normal thyroid hormones values in raccoons.
With the high suspicion of a functional thyroid neo-
plasm, incisional biopsy with histopathologic examination
of the tissue was recommended as well as potential chemo-
therapy treatment with Palladia (Toceranib phosphate) (2).
Given the lack of clinical symptoms related to the pathology,
the potential risks of a complicated surgical thyroid proce-
dure and the suspicion of pulmonary metastasis, further di-
agnostics and treatment were declined.
On a routine annual examination performed at 19 months
from the initial diagnosis, the reported raccoon and its two
male cage mates were clinically evaluated. Although not as
obese as before (currently 5.4 kg) or when compared to the two
other raccoons, this raccoon was still in good body condition (3
out of 5). Te thyroid masses on the neck had increased in size
and were diferent in palpation; the left was larger (~8.0 cm)
and felt more cystic and the right was smaller (~6.0cm) and
more solid to the touch. A blood sample was collected from
all three raccoons and analyzed for thyroxine (T4) (VetScan®
VS2, Abaxis, Union City, CA, USA), showing an elevated T4
Figure 2: Slide of the fne-needle aspirate showing cytology of the
ventral cervical mass in the raccoon. Modifed Wright stain, x40
objective.
Case Reports
Israel Journal of Veterinary Medicine  Vol. 69 (2)  June 2014 105 Tyroid Neoplasia in a Raccoon
(result>10.0 ug/dL [129mmol/L]; Abaxis Vetscn canine and
feline reference interval: 1.1-4.8 µg/dL [14.2-61.9 mmo/L]).
Te two other raccoons were within the normal reference in-
terval measuring 2.1 µg/dL and 2.0 µg/dL.
DISCUSSION
Tis case represents a unique presentation of thyroid pa-
thology in a captive raccoon. Tyroid neoplasms in raccoons
have been reported in Europe as well as one report in the
United States (3-5). A study in Germany found that 18 of 28
(64%) captive raccoons had thyroid lesions during necropsy,
ten of which (38%) were carcinomas (4). Another study in
Germany found 31 of 40 (78%) captive raccoons had thyroid
lesions during necropsy, 15 of which (38%) were carcinomas
and four (10%) were adenomas (6). In both of these studies
in Germany, pathology of the thyroid glands was described,
but no clinical description of the afected raccoons was giv-
en (3, 4). McCain et al. described two cases of thyroid neo-
plasia in older adult spayed female raccoons in the United
States (5). Interestingly, the current case was also an older
adult female raccoon. One of the cases reported by McCain
et al. was a unilateral, nonfunctional thyroid adenocarcino-
ma with eventual pulmonary metastasis and a normal tT4
(20.1 ηg/mL (63.9 ηmol/L); reference interval: 10-40 ηg/
mL (31.8-127.2 ηmol/L)) when compared to domestic dog
and cat reference intervals from the University of Tennessee.
Te other case described by McCain et al. was an obese ma-
ture female with no palpable cervical masses, and a lesion
described as a bilateral thyroid adenoma with elevated tT4
(80 ηg/mL (254.4 ηmol/L); reference interval: 10-40 ηg/mL
(31.8-127.2 ηmol/L)) and T3 (1.75 ηg/mL (5.57 ηmol/L);
reference interval: 0.5-1.5 ηg/mL (1.59-4.77 ηmol/L)) (5).
In the current case, the lesions were bilateral, the raccoon was
obese with no history of weight loss, and pulmonary metas-
tasis was suspected. Additionally, the tT4 and T3 values were
increased, though not as signifcantly as in the adenoma in
the case report from the United States (5).
Since little information is available on thyroid neoplasia
in raccoons, the behavior of thyroid tumors was investigated
in dogs and cats, where there is a vast array of information
available. In dogs, thyroid carcinomas are more common than
adenomas (7). Most thyroid carcinomas in dogs are large,
unilateral, nonfunctional, invasive, malignant neoplasms (5,
6). Hypothyroidism or hyperthyroidism can occur with ma-
lignant thyroid tumors in dogs (5, 6). In dogs, the metastatic
rate can be high with commonly reported sites of metasta-
sis to the lungs, retropharyngeal lymph nodes and the liv-
er (5, 6). Tyroid adenomas are more common in cats than
dogs and are often bilateral, functional neoplasms resulting
in hyperthyroidism (7). Functional thyroid tumors result in
clinical signs of hyperthyroidism as a result of the increased
production, secretion, and circulation of active thyroid hor-
mones, thyroxine (T4) and triiodothyronine (T3) (8). Te
vast majority (98%) of hyperthyroidism cases in cats are a
result of benign adenomatous hyperplasia or thyroid adeno-
ma (8). Common abnormalities on CBC in cats with hyper-
thyroidism include an increased packed cell volume (PCV),
macrocytosis, stress leukogram and megathrombocytosis, or
the CBC can be unremarkable (8), as was observed in the
current case. Common serum biochemistry abnormalities
include increased liver enzymes, with mild to moderately
increased ALP and/or alanine aminotransferase (ALT), in-
creases in blood urea nitrogen (BUN), and creatinine (8).
Increased ALP was also observed in the current case.
Te clinical fndings of a bilateral, thyroid mass without
vascular invasion in the current case might suggest that the
lesion is either a hyperplastic thyroid or a thyroid adenoma;
however, the pulmonary nodule is suspicious for metastasis,
which would be more likely with a thyroid carcinoma. Tere
are few cytologic features that help distinguish between ad-
enoma, carcinoma or hyperplasia. Histopathologic examina-
tion of the tissue to look for the presence of a capsule, invasion
into surrounding tissue, or compression of adjacent thyroid
tissue is required for a defnitive diagnosis. In the current case,
neoplasia was considered more likely because some of the cells
on cytologic examination displayed pleomorphism which is
more suggestive of neoplasia than hyperplasia.
Treatment of thyroid carcinoma in the raccoon reported
by McCain et al. consisted of a unilateral thyroidectomy, with
a repeat thyroidectomy when recurrence of the tumor was
noted and oral piroxicam and misoprostol following a third
recurrence and lung metastasis (5). A third cytoreduction
surgery was performed followed by intravenous doxorubicin
(5). Anorexia and pancytopenia developed following doxoru-
bicin administration and the raccoon was euthanized (5). Te
second case reported by McCain et al. of a functional thyroid
adenoma in a raccoon was treated with total thyroidectomy
of one side and partial thyroidectomy of the other side, as
well as methimazole gel (5).
Case Reports
Israel Journal of Veterinary Medicine  Vol. 69 (2)  June 2014 Gardhouse, S. 106
Treatment of thyroid carcinoma in dogs involves local
treatment with surgery, radiation, or both, or systemic treat-
ment with chemotherapeutic agents (7). Treatment options
for thyroid adenoma in cats include thyroidectomy, radioac-
tive iodine (
131
I) or anti-thyroid drugs such as methimazole
(7). Te treatment of choice in cats is radioactive iodine (9).
Te raccoon in this case received no treatments for either its
neoplasia or the thyroid hormone imbalance, thus suggest-
ing a diferent clinical behavior of this pathology in this case.
To date, 19 months from the time of the initial presentation,
the raccoon is doing well clinically with no obvious clinical
signs other than the palpable prominent cervical masses and
some weight loss.
Tis report suggests that thyroid neoplasia is a condition
that should be considered when raccoons present with cervi-
cal masses. Given the large number of captive raccoons with
thyroid pathology described in the studies from Germany, it
is probable this condition is more prevalent than the litera-
ture suggests at this time (3, 4). It can present as a nonfunc-
tional carcinoma as is most common in dogs, or a functional
adenoma as is most common in cats (3)
Tis case can add to the growing body of literature on this
relatively common disease condition in raccoons and can as-
sist clinicians that see similar cases; however, more cases are
required to obtain additional information about this condi-
tion in raccoons.
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Case Reports