CASE REPORT
A CASE REPORT ON ENLARGED THYMUS IN ADULT HUMAN
CADAVER
Jyoti Krian Kohli1
HOW TO CITE THIS ARTICLE:
Jyoti Krian Kohli. “A Case Report on Enlarged Thymus in Adult Human Cadaver”. Journal of Evidence Based
Medicine and Healthcare; Volume 1, Issue 3, May 2014; Page: 129-133.
ABSTRACT: An unusually enlarged Thymus is seen in superio anterior mediastinum interspersed
between aorta and superior vena cava, observed in adult male cadaver during routine dissection.
This finding could be mistaken as intrathymic lymph node. Thymus seems to appear at later half
of fetal period but function of persistent enlarged Thymus is still unknown although it is assumed
to play a different role in immune system than other peripheral lymph node. Such enlarged
Thymus in adults can lead to clinical syndromes similar to superior and anterior mediastinum
pressure symptoms.
KEYWORDS: Thymus, Immune system, Lymph Node, Mediastinum.
INTRODUCTION: The lymph node system and thymus constitutes the major part of lymphoid
tissues in mammalian organism.
The human Thymus is located in anterior mediastinum and overlies the pericardium. It
comprised of right and left lobes which is completely invested by fibrous capsule. The upper
portion cervical thymus and lower portion is thoracic thymus.(1)
Thymus being one of the two central organs of lymphoid system, other being bone
marrow is responsible for provision of thymus processed lymphocytes (T-Lymphocytes) to whole
body. It also has humoral secretory function and so may be regarded as an endocrine gland. It
varies in size and activity depending on age, disease and physiological status of body but remains
active even into old age.
At birth it weighs---10-15gms
Grows till puberty--30-40gms
Diminishes and replaced by adipose tissue to 10gms in middle age,
In some cases it may remain large and weigh 28-50gms.(2, 3)
Gross appearance:
In early life -- Pinkish grey, soft, finely lobulated.
Consist of two unequal, pyramidal lobes connected by loose connective tissue.
Embryologically its each lobe develops from 3rd pharyngeal pouch of same side.(4)
Extent of Thymus gland: Thymus lies in superior and anterior-inferior mediastinum extending
inferiorly to fourth costal cartilages. Its shape is moulded largely due to adjacent structures i.e.
posteriorly pericardium and aortic branches with its branches, left brachiocephalic vein and front
and side of trachea.
Small accessory nodules may occur in neck, representing portions of thymic diverticula
which became detached during their early descent. (4)
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CASE REPORT
MATERIALS AND METHODS: Thymus sample was obtained from cadaver during routine
dissection in SGT medical college, Gurgaon, Department of Anatomy. It was a cadaver of 34-36
yrs aged male body, cause of death was unknown. Tissue was later confirmed on histology as
Thymic tissue.
OBSERVATION: Tissue obtained was pyramidal in shape, Bifid from above.
Fig. 1: Dimension--length 7cms, width 3cms with maximum width up to 3.8cms, near lower end,
depth of 1/2cm.
Fig. 1 & 2
,
Fig. 3
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CASE REPORT
Fig. 4
RELATIONS (Fig. 2, 3, 4)
Anteriorly --- superior venae cavae, ascending aorta, Arch of aorta, left brachiocephalic vein.
Posteriorly --- trachea, vagus.
Right --------- Right lung, mediastinal pleura, phrenic Nerve, azygous vein, Hilum of lung.
Left ---------- trachea, arch of aorta and its branches.
Above ------ right subclavian artery, right and left Brachiocephalic vein.
DISCUSSION: As fatty infilteration occurs progressively from neonatal period onwards, if often
makes the distinction between the thymus and surrounding mediastinal adipose tissue difficult to
be recognized at postmortem, although it is always encapsulated.
The phylogenesis of lymphoid tissues starts in lower vertebrates (Jonsson and Christensen
1978). In adults the intrathymic lymphnodes (ITLN) gradually involute following thymic
involution. It is interesting to consider that fatty degeneration of ITLN may start from outer side,
which for peripheral lymph nodes usually occurs by replacement of parenchyma and adipose
tissue.(5)
The human ITLN and PTLN may be located down stream from the thymus. Some new
born T cells produced in thymus may enter these nodes because it is generally considered that
the human thymus has no afferent lymphatic vessels. (6)
Moreover self antigen and some antigen presenting cells may also enter these nodes from
the thymus (e.g macrophages/dendritic cells) through the lymphatics.
Some pheripheral lymphocytes may also enter these nodes through the HEV. These nodes
are likely to be the place for interaction between peripheral lymphocytes and cells from the
thymus.(8)
Role of intrathymic and parathymic lymph node is still unknown although it is suggested
that they play a role in immune system which differ from that of other peripheral lymph nodes on
basis of morphological characteristics of lymph node.(9)
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Clinical significance: As thymic functions are not yet completely clarified in recent years, but
major function is to achieve the differentiation of lymphocytes into different classes of T cells and
to maintain a sufficient supply of them in general circulation and peripheral lymphoid organs to
react to antigenic stimuli, may be present in body.(8)
Its interaction with other endocrine glands like--LH, FSH, Prolactin, TSH and somatotropic
hormones, also appears to be widespread.(3)
It has been seen that adrenelectomy causes thymic enlargement.
Removal of thymus in mice earlier in life leads to death from wasting disease.(4)
In young children a large thymus may press on trachea causing attacks of respiratory
stridor.
Thymic tumours can compress trachea, oesophagus and large veins of neck causing
hoarseness, cough, dysphagia and cynosis.
Myasthenia gravis a chronic autoimmune disease of adults(7) also seen to be associated
with enlarged thymus. Thus thymic disorders may reflect role of Thymus in modulating immune
response of whole body. Besides these enlargements can present as mediastinal syndromes and
can be observed as artefact in CT/MRI of chest also (especially if there is calcification anywhere).
REFERENCES:
1. Tanegashima a. Yamashita a. Yamamoto h. Fukunaga T, Human parathymic lymph node:
morphological and functional significance. Immunology (1999) 97.301-308.
2. Keynes G The physiology of the thymus gland. Br Med j (1954) 2: 659-663.
3. Kendall MD, Johnson HRM, Singh J The weight of human thymus gland at necropsy. J.
Anatomy (1980) 131: 485-499.
4. Williams L P, Warwick Roger, Dyson M, Bannister LH. Grays anatomy (1989) 37 editions. P;
833-838.
5. Luscieti P. Hubschmid TH. Coittier H. Hess MW. Sobin LH, Human lymph node morphology
as a function of age and site. Journal of clinical pathology (1980) 33, 454-461.
6. Golstein G. Mackay IR, The human thymus p-3, Heinemann London (1969), P-3.
7. CastlemanN B The pathology of thymus gland in Myasthenia gravis. Ann NY Acad Sci (1966)
135: 496-505.
8. Bailey RP. Weiss ontogeny of human fetal lymph nodes. American journal of Anatomy
(1975) 142; 15-28.
9. Bloodworth JMB Jr. Hiratsuka H. Hickey RC.WUJ, Ultra structure of human thymus, thymic
tumors and myasthenia gravis. In pathology annual (ed. Somers sc), (1975) vol. 10 .p329.
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AUTHORS:
1. Jyoti Kiran Kohli
PARTICULARS OF CONTRIBUTORS:
1. Associate Professor, Department of
Anatomy, SGT Medical College, Gurgaon,
Haryana.
NAME ADDRESS EMAIL ID OF THE
CORRESPONDING AUTHOR:
Dr. Jyoti Kiran Kohli,
E-12, 1st Floor,
Lajpat Nagar 1st,
New Delhi – 110024.
E-mail: jkk702003@yahoo.co.in
Date
Date
Date
Date
of
of
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Submission: 15/05/2014.
Peer Review: 16/05/2014.
Acceptance: 10/06/2014.
Publishing: 13/06/2014.
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