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

Balaiah, K

Nayak, Ganesh

Shetty, Prasad K

Shetty, Prasanna K

English

Cognitive Sciences ePrint Archive

Case Report:
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:
Dr. Prasad K Shetty,
Department of Pathology,
Bhagwan Mahaveer Jain Hospital,
Millers Road,
Bangalore-560052, India.
E-mail: dr.pkshetty@gmail.com
Citation: Shetty PK, Balaiah K, Nayak G, Shetty PK. Thymoma with Myasthenia Gravis in Adolescent. Online J Health Allied Scs.  
2010;9(4):16
URL: http://www.ojhas.org/issue36/2010-4-16.htm
Open Access Archives: http://cogprints.org/view/subjects/OJHAS.html and http://openmed.nic.in/view/subjects/ojhas.html
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
Case Report:
A 16 year old girl presented with difficulty in breathing, diffi-
culty in swallowing and on and off vomiting since 6 days, she 
gives history of herpes infection 3 months back. On examina-
tion her chest and cardiovascular exam were normal. Her neur-
ological examination reveled neck stiffness, neck flexor weak-
ness and poor reflex, an initial chest radiograph showed an an-
terior 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 me-
diastinum. There were no areas of chest wall or pericardial in-
vasion or lymphadenopathy.
Electroneuromyography (ENMG) was normal, repetitive nerve 
stimulation  (RNS) test  revealed neuromuscular  junction  dys-
function,  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 1: CT scan shows lobulated mass in the anterior me-
diastinum.
Figure 2: Well encapsulated thymoma with bossulated and 
smooth surface.
1
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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  ad-
mixed with lymphocytes. There was no evidence of capsular in-
vasion.
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 pa-
tient was continued with treatment for myasthenia gravis and 
was discharged on 12th post operative day.
Discussion:
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 pop-
ulation  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, caus-
ing shortness of breath, superior vena cava syndrome, or non-
specific 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 dis-
ease  is  characterized  by  easy  fatigability  and  fluctuating 
strength in skeletal muscles. Patients weaken rapidly with exer-
cise and generally worsen as the day progresses. The most com-
mon muscles affected in children are those supplied by the cra-
nial 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 postsyn-
aptic membrane. This is manifested by the presence of measur-
able antibodies to acetylcholine receptorsY2 as demonstrated in 
our patient.[4] The disease is counteracted by the use of antich-
olinesterase drugs. As many as 25% of thymomas are not detec-
ted by chest radiographs but are identified by CT scanning. CT 
remains an essential part of tumor staging, providing informa-
tion about tumor location and size and extent of involvement 
of, or invasion into, surrounding structures.[5]
The World Health Organization recently developed a classifica-
tion 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 inva-
sion
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 myas-
thenia gravis or another autoimmune disease, one might con-
sider 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 approxim-
ately 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.
2
References:
1. King  RM,  Telander  RL,  Smithson  WA  et  al. 
Primary mediastinal  tumors  in  children.  J Pediatr  
Surg 1982;5:512–20
2. Cohen AJ, Thompson L, Edwards FH et al. Primary 
cysts and tumors of the mediastinum.  Ann Thorac 
Surg 1991;51:378–384
3. Souadjian  JV,  Enriquez  P,  Silverstein  MN,  Pepin 
JM.  The  spectrum  of  diseases  associated  with 
thymoma. Arch Intern Med 1974;134:374. 
4. Simpson  JA.  Myasthenia  Gravis  And  Myasthenia 
Syndromes. In: Walton JN, Ed. Disorders of Volun-
tary  Muscle.  Edinburgh,  London,  New  York 
Churchill Livingston, 1974;665-666.
5. Bertelse S, Malmstrom J, Heerfordt J et al. Tumors 
of  the thymic  region—symptomatology,  diagnosis, 
treatment and prognosis. Thorax 1975;30:19–25
6. Masaoka A, Monden Y, Nakahara K et al. Follow-
ing study of thymoma with special reference to their 
clinical stages. Cancer 1981;48:2485–2492
7. Haniuda M, Miyazawa M, Yoshida  et al.  Is  post-
operative radiotherapy for thymoma effective?  Ann 
Surg 1996;224:219–224
8. Fornasiero A, Daniele O, Ghiotto C et al. Chemo-
therapy  for  invasive  thymoma.  A  13-year  experi-
ence. Cancer 1991;68:30–33
9. Legg MA, Brady WJ. Pathology and clinical behavi-
or  of  thymomas:  A  survey  of  5  1 cases.  Cancer 
1968;18(9):1131-1144.
10. Namba T. Brunner NG, Grob D. Myasthenia gravis 
in patients with thymoma with particular reference 
to onset after thymectomy. Medicine 1978;57:4.
11. Rodriguez M, Gomez MR, Howard FM, Taylor WF. 
Myasthenia  gravis  in  children:  Long-term  fol-
low-up. Ann Neurol 1983;13:504-510.
12. Cavanagh NPC. The role of  thymectomy in child-
hood  myasthenia.  Develop Med  Child  Neurol  
1980;22:668-674.
3


Chemotherapy for invasive thymoma. A 13-year experience.

Following study of thymoma with special reference to their clinical stages.

Is postoperative radiotherapy for thymoma effective? Ann Surg

Myasthenia Gravis And Myasthenia Syndromes. In: Walton

Myasthenia gravis in children: Long-term follow-up.

Myasthenia gravis in patients with thymoma with particular reference to onset after thymectomy.

Pathology and clinical behavior of thymomas:

Primary cysts and tumors of the mediastinum. Ann Thorac Surg

Primary mediastinal tumors in children.

The role of thymectomy in childhood myasthenia.

The spectrum of diseases associated with thymoma.

Tumors of the thymic region—symptomatology, diagnosis, treatment and prognosis.

Thymoma with Myasthenia Gravis in Adolescent

Prasad K Shetty,

Balaiah K,

Ganesh Nayak,

Prasanna K Shetty,

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Thymoma with Myasthenia Gravis in Adolescent

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