This document provides an overview of substernal goiters, which are enlarged thyroid glands that extend below the sternum. It defines substernal goiters and classifies them based on the percentage of the mass in the neck or chest. The document discusses the pathogenesis, clinical presentation, investigations including imaging studies, and management including thyroid suppression, radioiodine therapy, and surgical approaches. Surgery remains the primary treatment and can involve cervical, partial sternotomy, thoracotomy, or combined approaches depending on the extent of the mediastinal extension. Postoperative monitoring and potential complications are also outlined.
4. Introduction
⢠Goiter is enlargement of the thyroid gland
associated with a thyroid gland that is
functioning properly or not
⢠Defination of substernal goiter is variable
⢠Account less than 10% of all goiters and 5% to
6% of apparent mediastinal masses
⢠The management of mediastinal goiters is
challanging because of the complexity of
surgical procedures and associated risks
5. Principle of most
⢠Almost all arise from cervical thyroid
⢠Most are symptomatic
⢠Almost all are pathologically benign
⢠Most are euthyroid
⢠Most are adequately diagnosed and evaluated by
CT.
⢠Almost all can be removed transcervically.
⢠Most are anterior or lateral to the trachea
⢠Most of pts experience an improvement in
symptoms after surgery .
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6. Definition
⢠The definition of a substernal goiter in less clear
⢠Various definitions have been proposed
ďśA substernal goiter has been variously defined
as an enlarged gland
⢠With some portion remained permanently
retrosternal(Kocher).
⢠With its lower position remaining below the
sternal notch with the neck
hyperextended(Torre)
7. ďWith extension down to the aortic arch(Crileâs)
ďWith its lower border reaching the transverse
process of T4 vertebrae or below(Linskogâs)
ďWith greater than 50% of the great volume
presenting behind the sternum(Katlic)
ďWhen It requires mediastinal exploration and
dissection for removal(Lahey)
ďWhen the intrathoracic component appears to
extend more than 3cm from the thoracic
inlet(Escharpase)
8. Classification
⢠Several authors have attempted to offer various
classifications schemes for substernal goiter to
objectively describe the degree of substernal
extension
⢠Lahey classification according to the relationship
to the aortic arch
ďGrade 1- includes those extending nearly to the
arch of aorta
ďGrade 2- includes those extending to arch of
aorta or beyond
9. .....
ďśHiggins, in 1927, classified these goiters based
on relative percentage of the mass in the neck
or chest:
1. More than 50% in neck, substernal;
2. more than 50% in chest, partially
intrathoracic; and
3. more than 80% in chest, completely
intrathoracic
10. âŚ
⢠Cohen and cho graded substernal goiters
according to the percentage of the
intrathoracic component of the goiter
⢠Grade 1: 0-25%
⢠Grade 2: 26-50%
⢠Grade 3: 51-75%
⢠Grade 4: >75%
11. Pathogenesis
⢠Over 98% of substernal goiter derived from a
caudal migration of cervical goiters.
⢠Tends to migrate anterior to the trachea,
esophagus, RLN, subclavian vessels in 85-90% of
cases and to posterior mediastinum in 10%â
15%
⢠Contributing factors : negative intrathoracic
pressure, effect of gravity, large potential space
12. ⢠Several theories of pathogenesis includes;
ďDevelop from thyrothymic congenital rests in
the thyrothymic ligament⌠appear after surgery
ďEmbryological hyperdescent of thyroid tissue
ďIt may Start as exophytic nodule from thyroid
inferior pole and over time there is attenuation
of nodule-thyroid stalk
13. Primary mediastinal goiter
⢠The category of truly isolated mediastinal
tumors is controversial.
ďśTerms used to describe this situation have
included;
ďisolated
ďectopic
ďheterotopic, and
ďaberrant mediastinal/intrathoracic goiter
14. ďśEctopic thyroid has been reported
I. At the aortic root,
II. in the pericardium, and
III. within cardiac muscle or esophageal wall
15. Diagnostic criteria
⢠Completely separated from the gland in the
neck,
⢠Thoracic blood supply
⢠Normal or completely absent Cx thyroid
⢠No prior thyroid surgery
⢠No current or previous invasive thyroid
malignancy,
⢠No similar pathologic process in cervical and
so-called ectopic thyroid tissue
16. Clinical presentation
⢠More frequently in the fifth or sixth decades
⢠Thirty to forty percent are asymptomatic
⢠In about 20% no palpable neck mass
⢠10% to 20% of patients may have prior history
of surgery
ďśUpper airway obstruction can occur acutely
17. ďśIn Symptomatic cases
⢠The rates for symptoms are;
ďź cough, dyspnea, positional or nocturnal
breathing difficulty (35% to 96% of patients;
ďźdysphagia in 18% to 60%, and
ďźhoarseness in 10% to 26%
ďźvenous obstruction(~10%)
19. Ultrasonography FNAC & TFT
⢠Undertaken only if concern
of poorly differentiated
carcinoma and toxic nodule
exists
⢠Bony thorax limits visibility
⢠It can help to;
ď define the cervical extent
of disease
ď Assess parenchymal lesion
20. Chest or Neck x-ray
⢠Provides the first
evidence of a
mediastinal mass
⢠Overall correlation
between imaging studies
and symptoms of
substernal goiter is poor
⢠Can suggest substernal
thyroid masses in 60% to
90% of cases
21. CT scan
⢠A cross-sectional
imaging study with CT
or MRI provides the
most important
information for the
evaluation and planning
the surgical
approach to substernal
goiters
22. ⢠CT of the chest with
mediastinal goiter that
originates in the Rt lobe of
the thyroid and extends
down into the mediastinum
⢠It is heterogeneous and
enhancing.
23. Magnetic Resonance Imaging
⢠It provides excellent
information on
relationships to the
great vessels and
⢠it is superior at
detecting tracheal or
esophageal invasion
24. Indirect Laryngoscopy
⢠Absolutely indicated if there is any history of
hoarseness or concern for cord function
⢠At the time of surgery to see the condition of
the vocal cords and position of the larynx
⢠Post operatively to review cord function
26. Thyroid Suppression
⢠Attempted suppression with thyroxine is
generally ineffective and inappropriate,
⢠The effect is modest, delayed, unpredictable
and not durable
27. Radioiodine Therapy
⢠Might be necessary only when surgery is
precluded
⢠The full effect of radioiodine treatment is
unpredictable and often not evident for 3 to 6
months
⢠Complications
⢠Thyroiditis (âź5%),
⢠Need for second treatment (âź20%),
⢠Hypothyroidism (60%-100%)
⢠Radiation-induced Gravesâ disease (âź10%)
28. Surgery
⢠The diagnosis of substernal goiter is an absolute
indication
⢠Remain a great challenge to the operating
surgeon
⢠Distorted neck base anatomy, restricted surgical
access of the thoracic inlet, mediastinal
extension, increased size of the thyroid gland,
increase glandular vascularity has increased skill
demand
29. Surgical Intervention
⢠The extent of surgery can be;
ď bilateral total or near-total thyroidectomyâŚ
the lowest recurrence rate
or
ďunilateral surgery is an acceptable if
substernal goiter could arise clearly from just
one thyroid lobeâŚ. a higher recurrence rate
30. Surgical exposures
ďCervical- Nearly all (97%-99%) mediastinal
goiters
ďA partial upper sternotomy
ďCombining anterior thoracic and
transclavicular
ďvideo-assisted exposure with cervical
exposure
ďsimultaneously combine cervical and
posterolateral thoracotomy approaches
33. Recurrence
⢠Highly dependent on the extent surgery
⢠Can manifest after as long as 10 to 30
years
⢠Long-term studies report recurrence rates
of 15% to 60%
⢠More common in young females with a
family history of this diagnosis
⢠Treatment : radioactive iodine