Exam 3 - Endocrine Tumors Flashcards
what dog breeds are predisposed to thyroid tumors? what are these tumors diagnosed as histopathologically?
boxers, beagles, goldens, huskies
90% of tumors SUBMITTED are carcinomas or adenocarcinomas
what is the median age of diagnosis for dogs with thyroid tumors?
9-11 years old
commonly diagnosed concurrently with other cancers
what is the most common origin of canine thyroid tumors? what are the subclassifications of this tumor type? are they usually functional?
follicular cell (thyroglobulin-producing) origin - further classified as follicular, compact (solid), papillary, or anaplastic
majority are non-functional in dogs
where do we commonly see ectopic thyroid tissue in dogs?
base of the tongue
hyoid apparatus
cranial mediastinum
T/F: in dogs with thyroid tumors, right & left lobes of the thyroid are affected with equal frequency with 67-75% being unilateral & 25-33% being bilateral
true
_________ (parafollicular/c cells that produce calcitonin) may have a less aggressive behavior than follicular cell thyroid tumors
medullary cell thyroid tumors
what are the common presenting signs of thyroid tumors in dogs?
clinical signs are due to the mass effect or invasion of the tumor into adjacent tissues
dysphagia, voice change, laryngeal paralysis, horner’s syndrome, & dyspnea
what are the common sites of metastasis for canine thyroid tumors?
locoregional lymph nodes, lungs, & abdominal organs
what is the metastatic potential for canine thyroid tumors?
35-40% will have metastatic disease at the time of diagnosis
up to 80% will develop metastasis
what is the gold standard for diagnosing/staging canine thyroid tumors?
histopathology!!!!
what do you need to consider when deciding on FNA vs. biopsy for a thyroid tumor in a dog?
THESE ARE VERY VASCULAR!!!! DO NOT BIOPSY!!!!!!
can use ultrasound guidance for FNA - need histopathology for gold standard diagnosis
what is the benefit of doing a CT for a dog with a thyroid tumor?
pre-surgical planning, look at local lymph nodes, & need to evaluate invasiveness & vascularity of the tumor
when would you do scintigraphy for a dog with a thyroid tumor? what information will it provide?
if you are concerned that it is a functional tumor
it will identify local residual disease present post-op, look for ectopic tumors, lymph node mets
what is a 99mtc-pertechnetate scan? what information does it provide?
part of scintigraphy that requires that a functional thyroid tumor is capable of trapping 99mTc with in the thyroid cells
may determine the likelihood of radioactive iodine treatment
what is included for clinical staging of canine thyroid tumors?
physical exam - palpate & measure tumor
cbc, chem, UA, T4, +/- blood pressure
FNA
thoracic rads
CT - head, neck, & thorax
+/- scintigraphy
why are invasive tumors not great for surgery for canine thyroid tumors?
less amenable to surgery due to invasion into surrounding structures including the trachea, esophagus, carotid artery, & recurrent laryngeal nerve
what is the benefit of using advanced imaging for canine thyroid tumors as far as determining prognosis?
determines if the mass remains encapsulated or if it is invading surrounding structures
is size a predictor of whether a thyroid tumor can be surgically removed?
nope!
what is the exception of poor prognosis in regards to a bilateral thyroid tumor in a dog?
bilateral, non-invasive thyroid carcinomas can be treated surgically!!!!
what are the prognostic factors in regards to size of the primary thyroid tumor in a dog?
<20 cm - 14% chance of metastasis, 21-100 cm3 - 74% metastasis, & > 100 cm3 - 100% metastasis
which is worse prognostically for canine thyroid tumors - unilateral or bilateral tumors?
bilateral is worse - 16x higher risk of metastasis
if you have a dog with a thyroid tumor that you have found to be metastatic after clinical staging, what are your treatment options?
palliative therapy - surgery, radiation, & chemo
if you have a dog with a mobile thyroid tumor with no metastatic disease after clinical staging, what are your treatment options?
surgical excision
chemotherapy - if tumor size is > 5 cm, vascular invasion is present, or you have a bilateral thyroid carcinoma
if you have a dog with a fixed thyroid tumor with no metastatic disease after clinical staging, what are your treatment options?
radiation therapy/radioactive iodine therapy
potential chemo - if tumor size is > 5 cm, vascular invasion is present, or you have a bilateral thyroid carcinoma
what is the risk of doing radioactive iodine therapy for treating an invasive, metastatic, or functional thyroid tumor in a dog?
not widely available & causes permanent bone marrow suppression
when may you do radiation therapy for local disease control for a dog with a thyroid tumor? what are the median survival times?
done for invasive tumors that are not amenable to surgery
hypofractionated - MST 5 to 20 months
definitive hyperfractionated - MST 24.5 months
what is the treatment of choice for canine thyroid tumors that don’t have extensive tissue invasion?
surgery is the treatment of choice!
what are the possible complications of surgical removal of a thyroid tumor in a dog?
hemorrhage, hypoparathyroidism, & laryngeal paralysis
what is the prognosis for surgical removal of a mobile, unilateral thyroid tumor in a dog?
excellent - MST >36 months, 70% 2 year survival rate
what should be done prior to surgical removal of a canine thyroid tumor because of its vascularity?
blood type the animal & have products on hand!
what is the most commonly used chemo in dogs with thyroid tumors?
carboplatin
when may chemotherapy be considered for treatment of a dog with a thyroid tumor?
considered in dogs with large, non-resectable primary tumors and/or gross metastatic disease
T/F: radiation therapy for dogs with fixed thyroid carcinomas have a good MST of 24-45 months after treatment which is better than an attempt at surgical removal
true
what is the most common feline thyroid tumor in cats with hyperthyroidism?
multi-nodular adenomatous hyperplasia
what is the least likely tumor cause of hyperthyroidism in cats? what therapy is recommended?
malignant thyroid carcinomas - highly metastatic, 70% to regional lymph nodes & lungs
surgical excision recommended!!
T/F: 90% of dogs & cats have a single parathyroid mass
true
what are the most common parathyroid tumors we see? what cells do they arise from? what does this cause?
adenomas - cystadenoma, adenocarcinoma, & hyperplasia
arise from the chief cells of the parathyroid gland which secrete PTH - leads to hypercalcemia
what breed is predisposed to parathyroid tumors due to an autosomal dominant mode of inheritance?
keeshond
how are parathyroid tumors diagnosed?
inappropriately high serum PTH in the presence of ionized hypercalcemia
73% will have PTH WNL, but normal PTH in the face of hypercalcemia is ABNORMAL
what do you expect serum calcium, PTH, vitamin D, & phosphate levels to be in primary hyperparathyroidism?
calcium - increased
PTH - normal to increased
vitamin D - increased
phosphate - decreased
what do you expect serum calcium, PTH, vitamin D, & phosphate levels to be in secondary hyperparathyroidism?
calcium - decreased to normal
PTH - increased
vitamin D - decreased
phosphate - increased or decreased
what do you expect serum calcium, PTH, vitamin D, & phosphate levels to be in tertiary hyperparathyroidism?
calcium - increased
PTH - very increased
vitamin D - decreased
phosphate - increased
how many parathyroid glands can you remove safely without risking permanent hypoparathyroidism?
you can remove 3 of the 4!!!!
what is the long term prognosis for a patient after surgical removal of a parathyroid tumor?
excellent - about 10% experience recurrence
what must be very carefully monitored in patients that have just had a surgical removal of a parathyroid tumor?
development of hypocalcemia!!!!
need to get them on oral calcium supplementation, calcitriol, & IV calcium if indicated
what is the definitive therapy for parathyroid tumors?
removal of the hyperfunctioning glands - surgery is the treatment of choice
can also do ultrasound guided ablation
what is the hallmark of insulinomas?
normal or increased blood insulin in the presence of low blood glucose!!!
what are insulinomas?
tumor of the pancreatic beta cells that results in the excess secretion of insulin & other hormones (glucagon, somatostatin, GH, IGF-1)
what is the most common cancer in middle aged to older ferrets?
insulinomas - 21-25%
what are the clinical signs of insulinomas associated with?
signs are due to hypoglycemia!!!
dull mentation, star gazing, hind limb paresis, ptyalism, pawing at the mouth (ferrets), weakness, seizures, ataxia, & signs may be episodic
paraneoplastic peripheral neuropathy described in dogs
what are your main differentials you should consider for hypoglycemia?
sepsis
severe hepatic disease - cirrhosis or a shunt
addison’s disease
idiopathic - juvenile, neonate, hunting dog
starvation
iatrogenic - insulin overdose
lab error
paraneoplastic - insulinoma, hepatocellular carcinoma, leiomyoma/leiomyosarcoma
what is stage 1 metastasis of canine insulinomas?
only involves the pancreas
what is stage 2 metastasis of canine insulinomas?
pancreas & lymph node involvement
what is stage 3 metastasis of canine insulinomas?
distant mets
T/F: documenting normal to elevated insulin levels in the face of hypoglycemia supports the diagnosis of an insulinoma
true
what imaging may be used for diagnosing an insulinoma?
abdominal ultrasound - may be normal because many tumors can be super small, but still a good non-invasive test to look for the primary tumor & metastasis
dynamic CT or dual phase CT angiography may have a better sensitivity than ultrasound
what is the treatment of choice for insulinomas?
surgery!!! surgical explore, partial pancreatectomy, & lymph node removal if possible
what medical management is done for patients with insulinomas?
dextrose IV if an emergency situation!!!
prednisone - insulin antagonist that promotes gluconeogenesis & glycogenolysis
T/F: for insulinomas, stage of the disease is prognostic
true
what is the MST for dogs treated with surgery for an insulinoma?
758-1316 days!!!
T/F: insulinomas are rare in cats
true - survival times range from 1 month to 32 months
what are the 3 stages of disease for insulinomas in regards to prognosis?
stage 1 - 50% free of hypoglycemia 14 months post-op
stage 2-3 - <20% free of hypoglycemia 14 months post-op
stage 3 - metastasis developed at 6 months
what is the mechanism of action of streptozotocin? why use it for insulinomas? what are the risks?
alkylating agent that is selectively taken up by GLUT-2 transporters
medical management of insulinomas
nephrotoxicity, hepatotoxicity, & DM in 42% of dogs
what is the mechanism of action of diazoxide? why use it for insulinomas? what are the risks?
non-diuretic benzothiadiazine that suppresses insulin release from beta cells that 70% of dogs respond to & is fairly well tolerated
costly & limited availability
what is the mechanism of action of octreotide? why use it for insulinomas? what are the risks?
somatostatin receptor ligand that inhibits insulin synthesis & secretion that alleviates hypoglycemia in about 50% of dogs
rare side effects but costly
what is the mechanism of action of palladia (toceranib)? why use it for insulinomas? what are the risks?
small molecule inhibitor with an unknown mechanism
what do gastrinomas cause?
secrete excessive amounts of gastrin - non-beta cell neuroendocrine tumor of the pancreas causing hypergastrinemia & gi ulceration
almost all reported in the pancreas
why are gastrinomas so bad?
highly metastatic!!! identified in 85% of dogs & cats at the time of initial diagnosis
mets to liver, lymph nodes, spleen, peritoneum, small intestine, omentum
what clinical signs are seen with gastrinomas?
signs associated with gastric acid hypersecretion & gastric mucosal hyperplasia
what therapy may be used for gastrinomas?
cytoreductive surgery may help reduce secretory capacity of the tumor & enhance the efficacy of medical therapy
what cells do glucagonomas arise from?
very rare - alpha cells in the pancreas
what clinical signs are associated with glucagonomas?
necrolytic migratory erythema - hyperkeratosis, crusting, ulceration, erosions of the footpads, mucocutaneous junctions, external genitalia, pressure points, & ventral abdomen
what other concurrent issues are often occurring with glucagonomas?
diabetes mellitus, hypoaminoacidemia, & increased liver enzyme activity
how are glucagonomas treated?
surgical resection/cytoreductive surgery
metastasis at diagnosis is very common
what cells do intestinal carcinoids arise from? what clinical signs are seen? what is the treatment of choice for these?
VERY RARE - arise from neuroendocrine cells arising from the gi tract, liver, gall bladder, & pancreas - clinical signs associated with location
surgical resection if possible
metastasis at diagnosis is very common
