Table 2.

Details of cats identified with ectopic hyperfunctional thyroid tissue

Case number	Number of hotspots		Additional features on imaging	Palpable nodule	Previous surgery	Reason for referral	Histopathology	Treatment	Outcome	Long-term follow-up
	Neck	TI	Thorax
1	1		1	Mediastinal 1 cm diameter ST opacity on XR	Yes	R then L UT 2 years apart	Recurrence of hyperthyroidism	ND	LD radioiodine	Euthyroid within 4 weeks post treatment	Still alive and euthyroid 4.5 years post treatment
2		1	2		Yes	No	Owners interest in iodine treatment	ND	LD radioiodine	Euthyroid within 4 weeks post treatment	Lost to long-term follow-up
3	2	1	2		No	L then R UT	Recurrence of hyperthyroidism	ND	Carbimazole	Well controlled with medical management	Euthanased 5 months later with pancreatic neoplasia
4	2		1		Yes	UT	Recurrence of hyperthyroidism, large palpable goitre	ND	Carbimazole	Well controlled with medical management	Euthanased 10 months later for unknown reason; euthyroid at time of euthanasia
5	1	1	1	Very large thoracic area of IRU	Yes	No	Difficulty medicating	ND	LD radioiodine	T4 reducing but not yet euthyroid after 4 weeks	Developed CHF, died 4 weeks post treatment
6		1	1	Mediastinal ST opacity on XR	No	UT	Carcinoma and concurrent disease	Carcinoma	No treatment	Severe concurrent cystitis and liver disease, euthanased at time of diagnosis	NA
7	1	1	2		Yes	BT	Recurrence of hyperthyroidism	Adenoma	LD radioiodine	Remained hyperthyroid, successfully controlled with carbimazole treatment	Euthanased 2.5 years later with renal failure
8			2		No	Yes	Recurrence of hyperthyroidism	ND	Carbimazole	Stabilised with medical management	Lost to follow-up
9	1		1		Yes	Yes	Recurrence of hyperthyroidism	Adenoma	Carbimazole	Stabilised with medical management	Lost to follow-up
10			1		No	Yes	Recurrence of hyperthyroidism	ND	Carbimazole	Stabilised with medical management	Lost to follow-up
11	3	1	1	On initial scintigraphy multiple areas of IRU in neck/TI/thorax, raising suspicions of carcinoma. Scintigraphy repeated after removal of further nodules for histopathology	No	UT 3 months previously, further thyroid nodules removed when hyper-thyroid-ism recurred	Recurrence of hyperthyroidism and suspicion of carcinoma	Adenoma	LD radioiodine	T4 significantly reduced 5 weeks post treatment but not yet euthyroid	Lost to follow-up
12	2		1	Clinician suspicious of carcinoma because of multiple areas of IRU	Yes	2 L UT	Recurrence of hyperthyroidism	2 Nodules removed – both adenoma	Methimazole	Well controlled with medical management	Developed laryngeal squamous cell carcinoma a few months later, time of euthanasia unknown
13			2	Large area of IRU extending from inside thoracic inlet to heart base, clinician suspicious of carcinoma	Yes	UT 4 years previously	Persistence of hyperthyroidism following thyroidectomy	Adenoma	Surgical biopsy for histopathology, followed by LD radioiodine	Became hypothyroid; stabilised with thyroxine	Euthyroid (still on thyroxine) 2 years later then lost to further follow-up
14			1		No	No	Not recorded	ND	LD radioiodine	Unknown	Lost to follow-up
15	2		1	Extremely large area of IRU within mediastinum, connected to bilateral areas of IRU in neck	Yes	No	Owners interest in iodine treatment	ND	No apparent response to LD radioiodine, then treated with HD radioiodine	Euthyroid within 10 weeks post treatment	Lost to follow-up
16			1		No	No	Poor response to methimazole	ND	LD radioiodine	Euthyroid within 4 weeks post treatment	Still alive and euthyroid 3 years post-treatment
17	2	1	1		Yes	No	Lack of response to LD radioiodine	ND, FNA suggestive of carcinoma	HD radioiodine	Euthyroid within 10 weeks post treatment, became hypothyroid	Still alive and hypothyroid (on thyroxine) 2.5 years later
18			2		No	No	Poor response to methimazole and no palpable thyroid	ND	LD radioiodine	Euthyroid within 4 weeks post treatment	Still alive and euthyroid 21 months post treatment
19			1		No	3 UT 1 year apart	Persistence of hyperthyroidism following 3rd thyroidectomy	ND	LD radioiodine	Euthyroid within 4 weeks post treatment	Still alive and euthyroid 27 months post treatment
20			1	Very large thoracic area of IRU	No	Yes	Recurrence of hyperthyroidism	ND, FNA suggestive of carcinoma	HD radioiodine	Died 2 weeks following treatment, cause unknown	NA
21	1	1	1	Widespread uptake of pertechnetate throughout pulmonary fields	Yes	UT	Treatment for carcinoma	Carcinoma	HD radioiodine	Euthyroid within 10 weeks post treatment	Remained euthyroid, euthanased 25 weeks post treatment due to pancytopenia (FIV positive)
22	1	1	1		Yes	UT	Difficulty medicating and owners interest in iodine treatment	ND	LD radioiodine	Euthyroid within 4 weeks post treatment	Lost to follow-up
23	1		1		Yes	UT 8 months previously	Recurrence of hyperthyroidism and very large goitre led to suspicion of carcinoma	ND	LD radioiodine	T4 had reduced within 4 weeks post treatment but not euthyroid	5 Months post treatment still not euthyroid but T4 continuing to decrease
24	2	1	1	Very extensive area IRU involving both glands in cervical area extending into cranial thorax cystic appearance on ultrasound	Yes	Yes	Poor response to medical treatment and large goitre suspicious of carcinoma	FNA suggestive of carcinoma, biopsy planned but died before performed	Methimazole	Euthanased due to development of CHF during investigations	NA
25	2	1	1	1 Large area IRU involving both glands, down cervical region into thorax	Yes	No	Poor response to methimazole, large goitre	Adenomatous hyperplasia	LD radioiodine	No reduction in T4	Stabilised more easily on lower dose methimazole compared with pre-iodine, despite no reduction in T4 with radioiodine alone. Alive and euthyroid 15 months post treatment
26			1		No	No	Difficulty medicating	ND	LD radioiodine	Euthyroid within 4 weeks post treatment	Still alive and euthyroid 7 months post treatment
27	2	1			Yes	No	Difficulty medicating	Adenomatous hyperplasia	Surgery	Euthyroid post surgery	Lost to follow-up

R=right sided, L=left sided, ND=not done, FNA=fine needle aspirate, NA=not applicable.