THYROID GLAND
Dr.Mohanned Alshalah
LEC 3
THYROID NEOPLASM
Classification of thyroid neoplasm
Benign
Follicular adenoma
Malignant
Primary
Secondary
Follicular epithelium – differentiated
Follicular
Papillary
Follicular epithelium – undifferentiated
Anaplastic
Parafollicular cells
Medullary
Lymphoid cells
Lymphoma
Metastatic
Local infiltration
Benign tumours
Follicular adenomas present as clinically solitary nodules and the distinction
between a follicular carcinoma and an adenoma can only be made by histological
examination.
In the adenoma there is no invasion of the capsule or of pericapsular blood
vessels. Treatment is, therefore, by wide excision —preferably a lobectomy.
The remaining thyroid tissue is normal so that prolonged follow up is
unnecessary.
Malignant thyroid tumours
Differentiated thyroid carcinoma, particularly papillary, frequently follows
accidental irradiation of the thyroid in childhood. The incidence of follicular
carcinoma is high in endemic goitrous areas, possibly owing to TSH stimulation.
Malignant lymphomas can present in a patient known to have autoimmune
thyroiditis, so that the lymphocytic infiltration in the autoimmune process may be
an aetiological factor.
Short-latency aggressive papillary cancer is associated with the ret/PTC3
oncogene and later-developing, possibly less aggressive, cancers are associated
with ret/PTC1.
Relative incidence of primary malignant tumour of the thyroid gland :
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 3
Papillary carcinoma 60 %
Follicular carcinoma 20%
Anaplastic carcinoma 10%
Medullary carcinoma 5%
Malignant lymphoma 5%
Diagnosis of thyroid neoplasm
Diagnosis is obvious on clinical examination in most cases of anaplastic
carcinoma, although Riedel’s thyroiditis is indistinguishable.
It is not always easy to exclude a carcinoma in a multinodular goitre, and solitary
nodules, particularly in a young male patient, are always suspect.
FNAC in preoperative diagnosis has an important value.
Incisional biopsy may cause seeding of cells and local recurrence and is not
advised in a resectable carcinoma.
In an anaplastic and obviously irremovable carcinoma, however, incisional or core
needle biopsy is justified.
When a preoperative diagnosis is made, imaging with ultrasound, MRI or CT is
required for the assessment of the extent of the primary tumour. Imaging
provides valuable information on nodal involvement, which permits preoperative
planning for nodal dissection.
Frozen section histology has a limited role in thyroid surgery. It cannot reliably
differentiate between encapsulated benign and malignant follicular neoplasms
and is of more value in confirming whether nodes are involved with papillary
cancer, thereby influencing the extent of nodal surgery.
Papillary carcinoma
Most papillary tumours contain a mixture of papillary and colloid- filled follicles.
Histologically the tumour shows papillary projections and characteristic pale
empty nuclei (Orphan Annie-eyed nuclei). Papillary carcinomas are very seldom
encapsulated. foci may occur in the same lobe as the primary tumour or, less
commonly, in both lobes. They may be due to lymphatic spread in the rich
intrathyroidal lymph plexus or to multicentric growth.
Spread to the lymph nodes is common but blood-borne metastases are unusual
unless the tumour is extrathyroidal. The term extrathyroidal indicates that the
primary tumour has infiltrated through the capsule of the thyroid gland, although
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 3
minimal invasion of the sternothyroid muscle is much less significant than
infiltration into the oesophagus or trachea.
The term ‘occult carcinoma’ is applied to all papillary carcinomas less than 1 cm in
diameter. These have a uniformly excellent prognosis although those presenting
with nodal or distant metastases justify more aggressive therapy.
Follicular carcinoma
These appear to be macroscopically encapsulated but microscopically, there is
invasion of the capsule and of the vascular spaces in the capsular region.
Multiple foci are seldom seen and lymph node involvement is much less common
than in papillary carcinoma. Blood-borne metastases are more common and the
eventual mortality rate is twice that of papillary cancer.
Hurthle cell tumours are a variant of follicular neoplasm in which oxyphil (Hurthle,
Askanazy) cells predominate histologically. Hurthle cell cancers are associated
with a poorer prognosis.
Prognosis in differentiated thyroid carcinoma
Compared with most cancers the prognosis in differentiated thyroid carcinoma is
excellent. Although influenced by histological type, prognosis is much more
dependent on age at diagnosis, size of the tumour, metastatic disease and the
presence of either extrathyroidal spread (in papillary cancer) or major capsular
transgression (in follicular carcinoma).
Tumour–node–metastasis staging of thyroid cancer??
Surgical treatment
The conservative approach advocates lobectomy with isthmusectomy in most
patients with total thyroidectomy reserved for specific indications (those with
bilateral disease or judged to be in a high-risk category).
The more radical approach advocates routine total thyroidectomy often as a
staged procedure depending on the pathological findings of the initial lobectomy.
Additional measures
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 3
Thyroxine; It is standard practice to prescribe thyroxine (0.1–0.2 mg daily) for all
patients after operation for differentiated thyroid carcinoma to suppress
endogenous TSH production. Thyroid hormone replacement is obviously
necessary after total thyroidectomy and in the majority of patients after near
total thyroidectomy, and is usually given in the form of thyroxine.
Radioiodine; If metastases take up radioiodine they may be detected by scanning
and may be treated with large doses of radioiodine. For effective scanning, all
normal thyroid tissue must have been ablated, either by surgery or preliminary
radioiodine, and the patient must be hypothyroid to improve uptake.
Alternatively, synthetic recombinant TSH may be used to stimulate uptake.
Patients who require repeated radioiodine administration for scanning and
therapy, should be given tri-iodothyronine (40–60 μg daily–1) because it is much
shorter acting and, on stopping it, increased TSH secretion and thyroid avidity for
iodine recover quickly so that radioiodine may be given after several days.
The patient is thereby spared weeks of developing thyroid insufficiency after
stopping thyroxine before radioiodine may be given.
Thyroglobulin; The measurement of serum thyroglobulin is of value in the followup and in the detection of metastatic disease in patients who have undergone
surgery for differentiated thyroid cancer. This measurement may obviate the
need for serial radioactive iodine scanning but when a rise occurs, a scan will be
indicated to confirm and locate the metastatic disease.
Undifferentiated (anaplastic) carcinoma
This occurs mainly in elderly women. Local infiltration is an early feature of these
tumours with spread by lymphatics and by the bloodstream. They are extremely
lethal tumours and survival for more than 1—2 years after presentation is most
unusual. Many of these aggressive lesions present in an advanced stage with
tracheal obstruction and require urgent tracheal decompression.
The trachea may be decompressed and tissue obtained for histology by
isthmusectomy. Tracheostomy is best avoided.Radiotherapy should be given in all
cases and may provide a worthwhile period of palliation as may combination
chemotherapy.
Medullary carcinoma
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THYROID GLAND
Dr.Mohanned Alshalah
LEC 3
These are tumours of the parafollicular (C)-cells derived from the neural crest.
High levels of serum calcitonin and carcinoembryonic antigen are produced by
many medullary tumours. These levels fall after resection of a tumour and will
rise again if the tumour recurs. This is a valuable tumour marker in the follow-up
of patients with this disease. Diarrhoea is a feature in 30 per cent of cases and this
may be due to 5-hydroxytryptamine or prostaglandins produced by the tumour
cells.
Some tumours are familial and may account for 10—20 per cent of all cases.
Medullary carcinoma may occur in combination with adrenal
phaeochromocytoma and hyperparathyroidism in the syndrome known as
multiple endocrine neoplasia type IIa (MEN IIa).
The familial form of the disease frequently affects children and young adults
whereas the sporadic cases occur at any age with no sex predominance.
When the familial form is associated with prominent mucosal neuromas involving
the lips, tongue and inner aspect of the eyelids, with occasionally a Marfanoid
hahitus, the syndrome is referred to as MEN type IIb.
Treatment is by total thyroidectomy and either prophylactic or therapeutic
resection of the central and bilateral cervical lymphnodes.
Familial cases are now detected by genetic screening for the RET oncogene
mutations which identifies individuals who will develop medullary cancer later in
life. The genetic tests are supplemented by estimating serum calcitonin levels in
the basal state and after stimulation by either calcium or pentagastrin. A rise in
calcitonin levels under these circumstances should lead to a prophylactic
thyroidectomy.
Phaeochromocytoma must be excluded by measurement of urinary
catecholamine levels in all cases before embarking upon thyroid surgery to avoid
the potential hazards associated with this condition.
Malignant lymphoma
The response to irradiation is good and radical surgery is unnecessary once the
diagnosis is established by biopsy. (Trucut) or open biopsy is usually necessary.
The prognosis is good if there is no involvement of cervical lymph nodes.
Rarely, the tumour is part of widespread malignant lymphoma disease, and the
prognosis in these cases is worse.
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