Exam 3 - Endocrine Tumors

Question 1

what dog breeds are predisposed to thyroid tumors? what are these tumors diagnosed as histopathologically?

Answer 1

boxers, beagles, goldens, huskies

90% of tumors SUBMITTED are carcinomas or adenocarcinomas

Question 2

what is the median age of diagnosis for dogs with thyroid tumors?

Answer 2

9-11 years old

commonly diagnosed concurrently with other cancers

Question 3

what is the most common origin of canine thyroid tumors? what are the subclassifications of this tumor type? are they usually functional?

Answer 3

follicular cell (thyroglobulin-producing) origin - further classified as follicular, compact (solid), papillary, or anaplastic

majority are non-functional in dogs

Question 4

where do we commonly see ectopic thyroid tissue in dogs?

Answer 4

base of the tongue

hyoid apparatus

cranial mediastinum

Question 5

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

Answer 5

true

Question 6

_________ (parafollicular/c cells that produce calcitonin) may have a less aggressive behavior than follicular cell thyroid tumors

Answer 6

medullary cell thyroid tumors

Question 7

what are the common presenting signs of thyroid tumors in dogs?

Answer 7

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

Question 8

what are the common sites of metastasis for canine thyroid tumors?

Answer 8

locoregional lymph nodes, lungs, & abdominal organs

Question 9

what is the metastatic potential for canine thyroid tumors?

Answer 9

35-40% will have metastatic disease at the time of diagnosis

up to 80% will develop metastasis

Question 10

what is the gold standard for diagnosing/staging canine thyroid tumors?

Answer 10

histopathology!!!!

Question 11

what do you need to consider when deciding on FNA vs. biopsy for a thyroid tumor in a dog?

Answer 11

THESE ARE VERY VASCULAR!!!! DO NOT BIOPSY!!!!!!

can use ultrasound guidance for FNA - need histopathology for gold standard diagnosis

Question 12

what is the benefit of doing a CT for a dog with a thyroid tumor?

Answer 12

pre-surgical planning, look at local lymph nodes, & need to evaluate invasiveness & vascularity of the tumor

Question 13

when would you do scintigraphy for a dog with a thyroid tumor? what information will it provide?

Answer 13

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

Question 14

what is a 99mtc-pertechnetate scan? what information does it provide?

Answer 14

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

Question 15

what is included for clinical staging of canine thyroid tumors?

Answer 15

physical exam - palpate & measure tumor

cbc, chem, UA, T4, +/- blood pressure

FNA

thoracic rads

CT - head, neck, & thorax

+/- scintigraphy

Question 16

why are invasive tumors not great for surgery for canine thyroid tumors?

Answer 16

less amenable to surgery due to invasion into surrounding structures including the trachea, esophagus, carotid artery, & recurrent laryngeal nerve

Question 17

what is the benefit of using advanced imaging for canine thyroid tumors as far as determining prognosis?

Answer 17

determines if the mass remains encapsulated or if it is invading surrounding structures

Question 18

is size a predictor of whether a thyroid tumor can be surgically removed?

Answer 18

nope!

Question 19

what is the exception of poor prognosis in regards to a bilateral thyroid tumor in a dog?

Answer 19

bilateral, non-invasive thyroid carcinomas can be treated surgically!!!!

Question 20

what are the prognostic factors in regards to size of the primary thyroid tumor in a dog?

Answer 20

<20 cm - 14% chance of metastasis, 21-100 cm3 - 74% metastasis, & > 100 cm3 - 100% metastasis

Question 21

which is worse prognostically for canine thyroid tumors - unilateral or bilateral tumors?

Answer 21

bilateral is worse - 16x higher risk of metastasis

Question 22

if you have a dog with a thyroid tumor that you have found to be metastatic after clinical staging, what are your treatment options?

Answer 22

palliative therapy - surgery, radiation, & chemo

Question 23

if you have a dog with a mobile thyroid tumor with no metastatic disease after clinical staging, what are your treatment options?

Answer 23

surgical excision

chemotherapy - if tumor size is > 5 cm, vascular invasion is present, or you have a bilateral thyroid carcinoma

Question 24

if you have a dog with a fixed thyroid tumor with no metastatic disease after clinical staging, what are your treatment options?

Answer 24

radiation therapy/radioactive iodine therapy

potential chemo - if tumor size is > 5 cm, vascular invasion is present, or you have a bilateral thyroid carcinoma

Question 25

what is the risk of doing radioactive iodine therapy for treating an invasive, metastatic, or functional thyroid tumor in a dog?

Answer 25

not widely available & causes permanent bone marrow suppression

Question 26

when may you do radiation therapy for local disease control for a dog with a thyroid tumor? what are the median survival times?

Answer 26

done for invasive tumors that are not amenable to surgery hypofractionated - MST 5 to 20 months definitive hyperfractionated - MST 24.5 months

Question 27

what is the treatment of choice for canine thyroid tumors that don't have extensive tissue invasion?

Answer 27

surgery is the treatment of choice!

Question 28

what are the possible complications of surgical removal of a thyroid tumor in a dog?

Answer 28

hemorrhage, hypoparathyroidism, & laryngeal paralysis

Question 29

what is the prognosis for surgical removal of a mobile, unilateral thyroid tumor in a dog?

Answer 29

excellent - MST >36 months, 70% 2 year survival rate

Question 30

what should be done prior to surgical removal of a canine thyroid tumor because of its vascularity?

Answer 30

blood type the animal & have products on hand!

Question 31

what is the most commonly used chemo in dogs with thyroid tumors?

Answer 31

carboplatin

Question 32

when may chemotherapy be considered for treatment of a dog with a thyroid tumor?

Answer 32

considered in dogs with large, non-resectable primary tumors and/or gross metastatic disease

Question 33

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

Answer 33

true

Question 34

what is the most common feline thyroid tumor in cats with hyperthyroidism?

Answer 34

multi-nodular adenomatous hyperplasia

Question 35

what is the least likely tumor cause of hyperthyroidism in cats? what therapy is recommended?

Answer 35

malignant thyroid carcinomas - highly metastatic, 70% to regional lymph nodes & lungs surgical excision recommended!!

Question 36

T/F: 90% of dogs & cats have a single parathyroid mass

Answer 36

true

Question 37

what are the most common parathyroid tumors we see? what cells do they arise from? what does this cause?

Answer 37

adenomas - cystadenoma, adenocarcinoma, & hyperplasia arise from the chief cells of the parathyroid gland which secrete PTH - leads to hypercalcemia

Question 38

what breed is predisposed to parathyroid tumors due to an autosomal dominant mode of inheritance?

Answer 38

keeshond

Question 39

how are parathyroid tumors diagnosed?

Answer 39

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

Question 40

what do you expect serum calcium, PTH, vitamin D, & phosphate levels to be in primary hyperparathyroidism?

Answer 40

calcium - increased PTH - normal to increased vitamin D - increased phosphate - decreased

Question 41

what do you expect serum calcium, PTH, vitamin D, & phosphate levels to be in secondary hyperparathyroidism?

Answer 41

calcium - decreased to normal PTH - increased vitamin D - decreased phosphate - increased or decreased

Question 42

what do you expect serum calcium, PTH, vitamin D, & phosphate levels to be in tertiary hyperparathyroidism?

Answer 42

calcium - increased PTH - very increased vitamin D - decreased phosphate - increased

Question 43

how many parathyroid glands can you remove safely without risking permanent hypoparathyroidism?

Answer 43

you can remove 3 of the 4!!!!

Question 44

what is the long term prognosis for a patient after surgical removal of a parathyroid tumor?

Answer 44

excellent - about 10% experience recurrence

Question 45

what must be very carefully monitored in patients that have just had a surgical removal of a parathyroid tumor?

Answer 45

development of hypocalcemia!!!! need to get them on oral calcium supplementation, calcitriol, & IV calcium if indicated

Question 46

what is the definitive therapy for parathyroid tumors?

Answer 46

removal of the hyperfunctioning glands - surgery is the treatment of choice can also do ultrasound guided ablation

Question 47

what is the hallmark of insulinomas?

Answer 47

normal or increased blood insulin in the presence of low blood glucose!!!

Question 48

what are insulinomas?

Answer 48

tumor of the pancreatic beta cells that results in the excess secretion of insulin & other hormones (glucagon, somatostatin, GH, IGF-1)

Question 49

what is the most common cancer in middle aged to older ferrets?

Answer 49

insulinomas - 21-25%

Question 50

what are the clinical signs of insulinomas associated with?

Answer 50

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

Question 51

what are your main differentials you should consider for hypoglycemia?

Answer 51

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

Question 52

what is stage 1 metastasis of canine insulinomas?

Answer 52

only involves the pancreas

Question 53

what is stage 2 metastasis of canine insulinomas?

Answer 53

pancreas & lymph node involvement

Question 54

what is stage 3 metastasis of canine insulinomas?

Answer 54

distant mets

Question 55

T/F: documenting normal to elevated insulin levels in the face of hypoglycemia supports the diagnosis of an insulinoma

Answer 55

true

Question 56

what imaging may be used for diagnosing an insulinoma?

Answer 56

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

Question 57

what is the treatment of choice for insulinomas?

Answer 57

surgery!!! surgical explore, partial pancreatectomy, & lymph node removal if possible

Question 58

what medical management is done for patients with insulinomas?

Answer 58

dextrose IV if an emergency situation!!! prednisone - insulin antagonist that promotes gluconeogenesis & glycogenolysis

Question 59

T/F: for insulinomas, stage of the disease is prognostic

Answer 59

true

Question 60

what is the MST for dogs treated with surgery for an insulinoma?

Answer 60

758-1316 days!!!

Question 61

T/F: insulinomas are rare in cats

Answer 61

true - survival times range from 1 month to 32 months

Question 62

what are the 3 stages of disease for insulinomas in regards to prognosis?

Answer 62

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

Question 63

what is the mechanism of action of streptozotocin? why use it for insulinomas? what are the risks?

Answer 63

alkylating agent that is selectively taken up by GLUT-2 transporters medical management of insulinomas nephrotoxicity, hepatotoxicity, & DM in 42% of dogs

Question 64

what is the mechanism of action of diazoxide? why use it for insulinomas? what are the risks?

Answer 64

non-diuretic benzothiadiazine that suppresses insulin release from beta cells that 70% of dogs respond to & is fairly well tolerated costly & limited availability

Question 65

what is the mechanism of action of octreotide? why use it for insulinomas? what are the risks?

Answer 65

somatostatin receptor ligand that inhibits insulin synthesis & secretion that alleviates hypoglycemia in about 50% of dogs rare side effects but costly

Question 66

what is the mechanism of action of palladia (toceranib)? why use it for insulinomas? what are the risks?

Answer 66

small molecule inhibitor with an unknown mechanism

Question 67

what do gastrinomas cause?

Answer 67

secrete excessive amounts of gastrin - non-beta cell neuroendocrine tumor of the pancreas causing hypergastrinemia & gi ulceration almost all reported in the pancreas

Question 68

why are gastrinomas so bad?

Answer 68

highly metastatic!!! identified in 85% of dogs & cats at the time of initial diagnosis mets to liver, lymph nodes, spleen, peritoneum, small intestine, omentum

Question 69

what clinical signs are seen with gastrinomas?

Answer 69

signs associated with gastric acid hypersecretion & gastric mucosal hyperplasia

Question 70

what therapy may be used for gastrinomas?

Answer 70

cytoreductive surgery may help reduce secretory capacity of the tumor & enhance the efficacy of medical therapy

Question 71

what cells do glucagonomas arise from?

Answer 71

very rare - alpha cells in the pancreas

Question 72

what clinical signs are associated with glucagonomas?

Answer 72

necrolytic migratory erythema - hyperkeratosis, crusting, ulceration, erosions of the footpads, mucocutaneous junctions, external genitalia, pressure points, & ventral abdomen

Question 73

what other concurrent issues are often occurring with glucagonomas?

Answer 73

diabetes mellitus, hypoaminoacidemia, & increased liver enzyme activity

Question 74

how are glucagonomas treated?

Answer 74

surgical resection/cytoreductive surgery metastasis at diagnosis is very common

Question 75

what cells do intestinal carcinoids arise from? what clinical signs are seen? what is the treatment of choice for these?

Answer 75

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