الفهرس 
Physiological aspectsOnly 14 pages are availabe for public view
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Abstract
In the context of cancer statistics, thyroid cancers are not common place. It represents less than
1 % of all cases of human cancer. In reality, because of the fact that, many thyr oid cancers never
become cl ini cally apparent and as such as never d iagnosed, the true incidence is not known.
However , their incidence is reported to be about 25 cases per mill ion populati on per year.
It is wise to begi n such a subject by givi ng an interesti ng idea about the histor ical aspects.
Knowledge of the embryonic mi grat ion of the thyroid gland is essential in deal ing with the var
iety of midl ine embryologi c ontogeny. Embryology also prov ides a basi s for the adequate classi
ficati on and clar i fies some issues about some pathological cond itions especi ally the pr oblem
of the potentially mal ignant nature of the aberrant thyroid tissue.
The anatomy of the thyroid and the anatomical relati ons of blood vessels and nerves, give us an im
portant idea about deali ng wi th thyroid tumours surgical ly, and tak i ng technica l
considerations dur ing thyroid mani pulati on.
The lymphatic pattern of the thyr oid gland, gives us the informati on about spread of thyroi d
tumours and helps us in
the clinical presentation of thyroid cancer and in neck d issecti on.
Certain physiolog ical aspects of the chemical function of the thyroid gland , have a bear i ng on
the aeti ology, pathogenesis, and natura l hi story of thyroid nod ular ity in general and thyro id
cancer i n par ticular.
As regard to classi f ication of thyroid neoplasm, there are many d i fferent var ieties. However ,
from the practical poi nt of v iew, the simplest and best classif ication of thyroid carcinoma
based on the ma jor histological character istics i s namely; papillary, foll icular, med
ullary and anaplastic carcinoma.
Factors may affecti ng on thyr oid cancer are, geographic d istr ibut ion, racia l factor, age
factor and sex factor.
There are several factors which may have a relation to the aetiology of the thyr o id carcinoma as,
rad iati on, iod ine def iciency, elevated TSH, pa pi llary adenoma, solitary
thyr oid nod ule and genetic and fam i l ia l factor.
The papi llary pattern of thyroid carcinoma is the most common and slow growi ng of all thyroid
carcinomas. It accounts for about more than 50 percent of all types and is about 3 times more
common in females than males. Lympatic d i sseminati on is the ma in route of spread. Occult papi
llary
carcinoma is the tumour of d iamter less than 1.5 cm.
The foll icular type, is the second most common thyr oid cancer, mak i ng up about 25 percent of a
ll thyr oid cancers. It is d ivided into subtypes; encapsulated with m inimal capsular and
vascular invasion and non-capsulated with marked invas ion. Distincti on between
follicular adenoma and encapsulated follicular carcinoma may be d i fficult and requ ires
evaluation of multi ple sections from the interface of the tumour capsule and the thyroid gland.
Med ullary carcinoma is der ived from parafollicular cells ”C-cells” and it secretes calcitoni n
which can serve as a tumour marker. It constitutes about 10 percent of all thyr oid carcinomas with
eaual frequency in men and women and occurs in two basic forms, sporad ic form and familial form.
The familial version i s usually, but not always, a part of multi ple end ocr ine adenomatosis
syndromes (type IIA and IIB). It tends to metastasize early to lymph nodes.
Anaplastic or und i fferentiated type compr ises about 10 percent of all thyr oid carcinomas. It is
highly mal ignant lesion, slightly commoner in women than men, and is a tumour of old age and
character ised by extensive invasi on into the ad jacent structures.
Lymphoma; it is the commonest type of thyroid stromal neoplasm. The thyr oid is a rare site for pr
imary lymphoma.
Mali gnant lymphoma may be associ ated with chronic immune thyroid itis and chron ic Hashimoto’s
thyroid it is.
Metastatic carcinoma; the thyroid gland i s considered to
be an i n frequent site of.
metastasis from pr imary carcinoma of
other organs. This pecul1ar ity, because the thyr o id is one of the most r ichly arter ialized
tissue in the bod y.
Thyroid swelling which is progressi vely increasing in size and accompanied with cervica l
adenopathy, are the commonest presentation. Previ ous neck exposure to irrad iation
and family history of thyr oid carcinoma may be relevant to its development. Recurrent laryngeal
nerve involvement is a lmost pathognomonic of thyroid carcinoma.
Rad iology ad ultrasonogra phy may help in d iagnosis of thyroid carcinoma.
Fine need le aspiration bi opsy allows sampl ing of tissues
without surg ical biopsy, accuracy, speed and patient acceptance are gained. The proced ure in
combinati on with DNA analysis give us preoperati ve accurate d iagnosis.
Thyr oid function tests and antibody tests are non specif ic and of l imited d iagnostic
value.
Serum thyroid ca lcitonin level is important in d iagnosis of med ullar y carcinoma.
Regard ing to treatment of thyroid carcinoma, there are f ive therapeutic modal ities which may be
used alone or in
combination; rad ioactive
surgery (the main l ine of treatment ), iod ine,thyr o id hor mone, rad iotherapy, and
chemothera py. The use of these d i fferent modal ities should be i nd iv idual ized for each
patient depend ing upon the pathological classif icati on of the tumour, the stage of
i nvasi on, the age of the patient and the location of the pr imary lesion. The goal of thyroid
cancer surgery should be to max imize therapeut le effectiveness whi le minimizing
iatrogenic mor bidity.
There are some techn ical considerati ons in surgical management of thyroid carcinoma. A new
technique for intra operative scintigraphy has recently developed .
Also, compl icati ons of surgical management must be considerated to avoid and to manage them.
The following factors have been shown to inf luence the prognosis; age, sex, size and extent of
pr imary tumour ,
histological type, presence and extent of blood vessels invasion, presence and extent of capsular
invasion, extent of surger y and ad juncti ve post operative therapy.