|
OJHAS Vol. 9, Issue 4:
Oct-Dec, 2010) |
|
|
| Thymoma
with Myasthenia Gravis in Adolescent |
|
Prasad K Shetty,
Balaiah K,
Ganesh Nayak,
Prasanna K Shetty,
Department of Pathology,
Cardiovascular Surgery, Bhagwan Mahaveer Jain Hospital, Bangalore, India and Department
of Pediatrics, Vaatsalya Hospital, Gokul Road, Hubli, India. |
|
|
| |
|
|
|
|
|
|
Address For Correspondence |
Department
of Pathology,
Bhagwan
Mahaveer Jain Hospital,
Millers
Road,
Bangalore-560052,
India.
E-mail:
dr.pkshetty@gmail.com |
|
|
|
|
|
Shetty PK, Balaiah K, Nayak G, Shetty PK. Thymoma
with Myasthenia Gravis in Adolescent. Online J Health Allied Scs.
2010;9(4):16 |
|
|
|
|
Submitted: Nov 1,
2010; Accepted: Nov 3, 2010; Published: Jan 20, 2011 |
|
|
|
|
|
|
|
| |
|
| Abstract: |
|
Thymomas are
exceedingly rare in the first 20 years of life, Thymic lesions comprise
approximately 2–3% of all pediatric mediastinal tumors and include
thymic cysts, hyperplasia, carcinoma, and thymomas. Fewer than 30 cases
in children have been described in the literature. Thymomas in adults
are commonly associated with other diseases, the most frequent being
myasthenia gravis. However, this association has been rarely reported
in childhood. These tumors are typically aggressive, with poor
outcomes. We report a case of thymoma associated with myasthenia gravis
in a 16-year-old girl and review the literature.
Key Words: Mediastinal
mass; Thymoma; Myasthenia Gravis
|
|
A 16 year old girl presented
with difficulty in breathing, difficulty in swallowing and on and off
vomiting since 6 days, she gives history of herpes infection 3 months
back. On examination her chest and cardiovascular exam were normal.
Her neurological examination reveled neck stiffness, neck flexor weakness
and poor reflex, an initial chest radiograph showed an anterior mediastinal
mass extending to the right of the ascending aorta. A computed tomographic
(CT) scan showed a lobulated 15x12cm non-fat-containing soft tissue
mass in the anterior mediastinum. There were no areas of chest wall
or pericardial invasion or lymphadenopathy.
 |
|
Figure 1: CT scan shows lobulated
mass in the anterior mediastinum. |
Electroneuromyography (ENMG)
was normal, repetitive nerve stimulation (RNS) test revealed neuromuscular
junction dysfunction, her serum anti acetylcholinestrase receptor antibody
level was 9.28nmol/L (Normal range being <0.3nmol/L). Based on
radiological and biochemical features patient was diagnosed as thymoma
associated with myasthenia gravis and was treated with neostigmine,
glycopyrrolate and plasmapheresis 3 hours/day for 7 days followed by
an exploratory thoracotomy and a resection of the mediastinal mass were
performed. On gross examination it was a well encapsulated mass measuring
14x11x8cms, outer surface was bossulated and smooth and cut surface was
gray white solid with zig zag nodules.
 |
|
 |
|
Figure 2: Well
encapsulated thymoma with bossulated and smooth surface. |
|
Figure 3: Cut surface of thymoma with zig zag gray white nodules. |
Microscopy showed well
encapsulated tumor, tumor cells were arranged in sharply defined, angular
lobules with motting and trabeculation (caused by epithelial-lymphocyte),
epithelial cells were spindly with fine chromatin with occasional mitosis
admixed with lymphocytes. There was no evidence of capsular invasion
 |
|
 |
|
Figure 4,5: Microphotograph 40x Hematoxylin and eosin shows thymoma
comprising of admixture of epithelial cells and lymphocytes. |
Based on the pathological
findings a diagnosis of Thymoma (World Health Organization classification
Type AB and Masaoka classification Stage I) was made. Postoperatively
patient was continued with treatment for myasthenia gravis and was discharged
on 12th post operative day.
The association of thymoma
and MG is well described in adults, occurring in anywhere from 10% to
59% of patients in adults. However, it has been stated that this association
rarely occur in children. Most mediastinal tumors in the pediatric population
are either neurogenic in origin (33%) or lymphomas (41%).[1]
Primary thymic lesions (such as thymic cysts, thymolipomas, and thymic
hyperplasia) represent only 2.5% of mediastinal tumors [2–4], while
thymomas comprise about 1%. Presenting signs are from mass effect in
the mediastinum, causing shortness of breath, superior vena cava syndrome,
or nonspecific complaints of discomfort.[1,2]
The incidence of Myasthenia
gravis in the general population is thought to be 0.5/100,000 to 3/100,000,
and approximately 1% of all patients with Maysthenia gravis are children.[3]
The disease is characterized by easy fatigability and fluctuating strength
in skeletal muscles. Patients weaken rapidly with exercise and generally
worsen as the day progresses. The most common muscles affected in children
are those supplied by the cranial nerves. The defect underlying the
disease is thought to be a result of an autoimmune mechanism that causes
a decrease in the number of available acetylcholine receptors on the
postsynaptic membrane. This is manifested by the presence of measurable
antibodies to acetylcholine receptorsY2 as demonstrated in our patient.[4]
The disease is counteracted by the use of anticholinesterase drugs.
As many as 25% of thymomas are not detected by chest radiographs but
are identified by CT scanning. CT remains an essential part of tumor
staging, providing information about tumor location and size and extent
of involvement of, or invasion into, surrounding structures.[5]
The World Health Organization
recently developed a classification system (Table 1), although
most reports follow the general principles outlined by Masaoka et al
(Table 2).[6]
|
Table
1: Who Classification
|
|
Type |
Histologic Description |
|
A |
Medullary Thymoma |
|
AB |
Mixed Thymoma |
|
B1 |
Predominently Cortical Thymoma |
|
B2 |
Cortical Thymoma |
|
B3 |
Well- differentiated Thymic carcinoma |
|
C |
Thymic Carcinoma |
|
Table
2: Masoka Classification |
| Stage I |
Encapsulated tumor with no gross or
microscopic invasion |
| Stage II |
Macroscopic invasion into the mediastinal
fat or pleura or microscopic invasion into the capsule |
| Stage III |
Invasion of the pericardium, great vessels,
or lung |
| Stage IVa |
Pleural or pericardial dissemination |
| Stage IVb |
Lymphogenous or Hematogenous metastases |
Thymoma is sensitive
both to chemotherapy and radiation, complete surgical resection is the
most in a patient with myasthenia gravis or another autoimmune disease,
one might consider a complete excision initially, rather than a biopsy,
in order to decrease any potential seeding of surrounding tissues.[7,8]
The relationship between thymoma and MG remains unclear. Treatment in
juvenile MG includes anticholinesterase drugs and prednisone. Thymectomy
has been performed on patients who were refractory to drug therapy.[7]
The natural course of MG in children is not well described, although
several recent reviews would suggest a nearly normal life expectancy,
with approximately 80% alive at 40 years of Respiratory failure is a
common cause of death in MG and was a serious problem in our patient.[9,10]
Several factors may precipitate respiratory compromise,
including infections, surgery, emotional stress, decrease in dose of
anticholinergic medication, or use of other medications such as aminoglycosides
and muscle relaxants.[11,12]
In summary, the association
of MG and thymoma, although rare, does occur in the pediatric population.
We report a 16-year-old girl with this association.
- King RM, Telander
RL, Smithson WA et al. Primary mediastinal tumors in
children. J Pediatr Surg 1982;5:512–20
-
Cohen AJ, Thompson
L, Edwards FH et al. Primary cysts and tumors of the
mediastinum. Ann Thorac Surg 1991;51:378–384
-
Souadjian JV, Enriquez
P, Silverstein MN, Pepin JM. The spectrum of diseases associated
with thymoma. Arch Intern Med
1974;134:374.
- Simpson JA. Myasthenia Gravis And
Myasthenia Syndromes. In: Walton JN, Ed.
Disorders of Voluntary Muscle. Edinburgh, London, New York Churchill Livingston, 1974;665-666.
-
Bertelse S, Malmstrom
J, Heerfordt J et al. Tumors of the thymic region—symptomatology,
diagnosis, treatment and prognosis. Thorax 1975;30:19–25
-
Masaoka A, Monden
Y, Nakahara K et al. Following study of thymoma with
special reference to their clinical stages. Cancer 1981;48:2485–2492
-
Haniuda M, Miyazawa
M, Yoshida et al. Is postoperative radiotherapy for thymoma
effective? Ann Surg 1996;224:219–224
-
Fornasiero A, Daniele
O, Ghiotto C et al. Chemotherapy for invasive thymoma.
A 13-year experience. Cancer 1991;68:30–33
-
Legg MA, Brady WJ.
Pathology and clinical behavior of thymomas: A survey of
5 1 cases. Cancer 1968;18(9):1131-1144.
-
Namba T. Brunner
NG, Grob D. Myasthenia gravis in patients with thymoma with particular
reference to onset after thymectomy. Medicine
1978;57:4.
-
Rodriguez M, Gomez MR, Howard FM, Taylor WF. Myasthenia gravis in children: Long-term
follow-up. Ann Neurol 1983;13:504-510.
-
Cavanagh NPC. The
role of thymectomy in childhood myasthenia. Develop Med
Child Neurol 1980;22:668-674.
|
