Thymoma overview: Difference between revisions

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Latest revision as of 23:11, 31 May 2019

IEditor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Amr Marawan, M.D. [2] Ahmad Al Maradni, M.D. [3]

Overview

Thymoma is a benign thymic neoplasm located in the anterior mediastinum, behind the sternum and in front of the great vessels that involutes during puberty, it takes part in lymphocytes maturation throughout adulthood.
The incidence of thymoma is approximately 0.13 per 100,000 individuals.
Thymic neoplasm can be divided into two major groups: thymoma and thymic carcinomathymoma
Thymoma is the most common tumor of the anterior mediastinum, consisting of any type of thymic epithelial cell as well as lymphocytes that are usually abundant and probably not neoplastic.
Thymoma usually is benign, and frequently encapsulated uncommon tumor, best known for its association with the autoimmune disorder such as myasthenia gravis. Thymoma is found in 15% of patients with myasthenia gravis.
Once diagnosed, thymomas may be removed surgically. If left untreated thymoma may progress to invade the mediastinum and the surrounding structure.
Depending on the stage of the tumor at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good.
Common complications of the thymoma include the pressure effect of the mass itself, autoimmune diseases, and rarely, malignancy. Metastasis is extremely rare. In the rare case of a malignant tumor, chemotherapy may be used.
Malignant lymphomas that involve the thymus, e.g., lymphosarcoma, Hodgkin's disease (termed "granulomatous thymoma" in the past), should not be regarded as thymoma.
Thymomas associated with autoimmune disorders usually are benign. Malignant thymomas can metastasize, generally to pleura, kidney, bone, liver, or brain.

Historical Perspective

The thymic epithelial tumors staging was initially proposed by Bergh and his colleagues in 1978, modified by Wilkins and Castleman in 1979, and advanced by Masaoka et al. in 1981.

Classification

In 1999, a World Health Organization (WHO) Working group suggested a non-committal terminology (Masaoka classification), preserving the distinct categories of the histogenetic classification, but using letters and numbers to designate tumour entities.
Recently, it has been very well accepted as it provides an easy comparison of clinical, pathological and immunological studies.

Pathology

On gross pathology, well circumscribed mass, that is locally invasive is a characteristic finding of thymoma.
On microscopic histopathological analysis, round cells, with ample vacuolated cytoplasms, and fat droplets are characteristic findings of thymoma.

Causes

There are no established causes for thymoma.

Differential Diagnosis

Thymoma must be differentiated from other thymic diseases such as

Epidemiology and Demographic

The incidence of thymoma is approximately 0.13 per 100,000 individuals.
Thymic neoplasms are the most common tumors located in the anterior mediastinum (20%).
Incidence increases in middle age, and peaks in the seventh decade of life.
Men and women are equally affected.

Risk Factors

There are no established risk factors for thymoma.

Natural History, Complication and Prognosis

If left untreated thymoma may progress to invade the mediastinum and the surrounding structure. Depending on the stage of the tumor at the time of diagnosis, the prognosis may vary.
The prognosis is generally regarded as good.
Common complications of the thymoma include the pressure effect of the mass itself, autoimmune diseases, and rarely, malignancy.

Diagnosis

History and symptoms

Symptoms of thymoma include

In addition to the symptoms of associated immune syndromes such as,

Physical examination

Patients with thymoma usually appear asymptomatic. Physical examination of patients with thymoma is may be remarkable for,

Neck lump,
Facial swelling
wheezing.

Staging

Staging of thymic epithelial tumors was initially proposed by Bergh and his colleagues in 1978, modified by Wilkins and Castleman in 1979, and advanced by Masaoka et al. in 1981.
Modified Masaoka staging grouped with TNM classification is the most widely adopted system for thymic epithelial tumors currently in use.

Laboratory Findings

Laboratory findings associated with thymoma may include,

Antibodies to the acetylcholine receptor,
Abnormal electrolytes, renal, and liver function tests.

X-Ray

On chest x-ray, thymoma is characterized by oval to rounded, well demarcated, asymmetric, homogeneous mass of soft tissue density on one side of the midline.

CT Scan

Computed Tomography scan may be diagnostic of thymoma. The tumor is generally located inside the thymus, and can be calcified.
Increased vascular enhancement can be indicative of malignancy, as can be pleural deposits.

MRI

On thoracic MRI, thymoma is characterized by increased heterogenous signal on T2WI.

Ultrasound

Ultrasound is used to guide fine needle aspiration or core needle biopsy in patients with thymoma.

Other Imaging Studies

PET scan may be used in the diagnosis of thymoma.

Other Diagnostic Studies

Other diagnostic studies for Thymoma include

CT scan guided core needle biopsy
CT scan guided fine needle aspiration
mediastinoscopy
Videothoracoscopy.

Treatment

Medical Therapy

Chemotherapy and radiotherapy are used as adjuvant or neoadjuvant therapies.
Neoadjuvant therpy may be administered prior to surgery to make the tumor resectable.

Surgery

Surgery is the mainstay of treatment of thymoma.

Primary Prevention

There are no primary preventive measures available for thymoma.

Secondary Prevention

Complete surgical resection may help to prevent the recurrence of thymoma.

References

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@@ Line 1: / Line 1: @@
 __NOTOC__
 {{Thymoma}}
-{{CMG}} {{AE}} {{AM}}
+I{{CMG}}; {{AE}} {{AM}} {{AAM}}
 ==Overview==
+* Thymoma is a [[benign]] thymic neoplasm located in the [[anterior mediastinum]], behind the sternum and in front of the great vessels that involutes during [[puberty]], it takes part in [[lymphocytes]] maturation throughout adulthood.
+* The incidence of thymoma is approximately 0.13 per 100,000 individuals.
+* Thymic neoplasm can be divided into two major groups: [[thymoma]] and [[thymic carcinoma]]thymoma
+* Thymoma is the most common tumor of the anterior [[mediastinum]], consisting of any type of thymic [[epithelial cell]] as well as [[lymphocyte]]s that are usually abundant and probably not [[neoplastic]].
+* Thymoma usually is [[benign]], and frequently encapsulated uncommon tumor, best known for its association with the autoimmune disorder such as [[myasthenia gravis]]. Thymoma is found in 15% of patients with [[myasthenia gravis]].
+* Once diagnosed, thymomas may be removed surgically.  If left untreated thymoma may progress to invade the [[mediastinum]] and the surrounding structure.
+* Depending on the stage of the tumor at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as good.
+* Common complications of the thymoma include the pressure effect of the mass itself, [[autoimmune diseases]], and rarely, [[malignancy]].  [[Metastasis]] is extremely rare. In the rare case of a [[malignant tumor]], [[chemotherapy]] may be used.
+* Malignant [[lymphomas]] that involve the [[thymus]], e.g., [[lymphosarcoma]], [[Hodgkin's disease]] (termed "granulomatous thymoma" in the past), should not be regarded as thymoma.
+* Thymomas associated with autoimmune disorders usually are benign. Malignant thymomas can [[metastasis|metastasize]], generally to [[pleura]], [[kidney]], [[bone]], [[liver]], or [[brain]].
-[[Thymoma]] is one of the organs contained in the [[anterior mediastinum]], located behind the sternum in front of the great vessels that involutes during puberty, but continues to take part in lymphocytes maturation throughout adulthood. Thymic malignancies count for less than 0.13/100,000/year.
+==Historical Perspective==
+* The thymic epithelial tumors staging was initially proposed by Bergh and his colleagues in 1978, modified by Wilkins and Castleman in 1979, and advanced by Masaoka et al. in 1981.
-They can be divided into two major groups: [[thymoma]] and [[thymic carcinoma]]. Prognosis and proper management are essentially determined by pathologic classification. Surgery is the only curative treatment, but they can be sensitive to chemotherapy and radiotherapy especially in unresectable disease.
+==Classification==
+* In 1999, a World Health Organization (WHO) Working group suggested a non-committal terminology (Masaoka classification), preserving the distinct categories of the histogenetic classification, but using letters and numbers to designate tumour entities.
+* Recently, it has been very well accepted as it provides an easy comparison of clinical, pathological and immunological studies.
-[[Thymoma]] is the most common tumor of the anterior mediastinum, consisting of any type of thymic [[epithelial cell]] as well as [[lymphocyte]]s that are usually abundant and probably not [[neoplastic]].  Thymoma usually is [[benign]], and frequently encapsulated uncommon tumor, best known for its association with the neuromuscular disorder [[myasthenia gravis]]. Thymoma is found in 15% of patients with [[myasthenia gravis]]. Once diagnosed, thymomas may be removed surgically.  When occasionally [[malignant]], then it is [[invasive]]:  [[metastasis]] is extremely rare. In the rare case of a malignant tumor, chemotherapy may be used.
+==Pathology==
+* On [[gross pathology]], well circumscribed [[mass]], that is locally invasive is a characteristic finding of thymoma.
+* On microscopic [[histopathological]] analysis, round cells, with ample vacuolated [[cytoplasm]]s, and fat droplets are characteristic findings of thymoma.
-Malignant [[lymphomas]] that involve the thymus, e.g., [[lymphosarcoma]], [[Hodgkin's disease]] (termed "granulomatous thymoma" in the past), should not be regarded as thymoma.<ref name=Thomas1999>{{cite journal |author=Thomas CR, Wright CD, Loehrer PJ |title=Thymoma: state of the art |journal=J. Clin. Oncol. |volume=17 |issue=7 |pages=2280–9 |year=1999 |pmid=10561285 |doi=}}</ref>
+==Causes==
+* There are no established causes for thymoma.
-Thymomas associated with autoimmune disorders usually are benign. Malignant thymomas can [[metastasis|metastasize]], generally to [[pleura]], [[kidney]], [[bone]], [[liver]] or [[brain]].<ref name="pmid10561285">{{cite journal |author=Thomas CR, Wright CD, Loehrer PJ |title=Thymoma: state of the art |journal=[[Journal of Clinical Oncology : Official Journal of the American Society of Clinical Oncology]] |volume=17 |issue=7 |pages=2280–9 |year=1999 |month=July |pmid=10561285 |doi= |url=http://www.jco.org/cgi/pmidlookup?view=long&pmid=10561285 |accessdate=2012-01-18}}</ref>
+==Differential Diagnosis==
+Thymoma must be differentiated from other thymic diseases such as
+* [[thymic carcinoma]]
+* Thymic [[cyst]]
+* Thymic [[hyperplasia]]
+* [[germ cell tumors]].
-====Pathophysiology====
+==Epidemiology and Demographic==
-In 1999, a WHO Working group suggested a non-committal terminology (Masaoka classification), preserving the distinct categories of the histogenetic classification, but using letters and numbers to designate tumour entities. Recently, it has been very well accepted as it provides an easy comparison of clinical, pathological and immunological studies
+* The incidence of thymoma is approximately 0.13 per 100,000 individuals.
-====Epidemiology and Demographics====
+* Thymic [[neoplasms]] are the most common tumors located in the [[anterior mediastinum]] (20%).
-Thymic neoplasms are the most common tumors located in the anterior mediastinum (20%). Thymoma is a rare malignancy of unknown etiology that accounts for 0.2–1.5% of all malignancies. It's incidence in the U.S. population is 0.13 per 100,000 person-years.
+* [[Incidence]] increases in middle age, and peaks in the seventh decade of life.
-====Risk Factors====
+* Men and women are equally affected.
-Most available evidence regarding risk factors for thymoma derives from descriptive epidemiologic studies of thymoma and associated malignancies. Unfortunately, no available data concerning the role of occupation, environmental exposures, or diet and nutrition.
-====Complications and Prognosis====
-The main prognostic factors for recurrence and survival are the stage at diagnosis and whether a complete resection has been achieved. Other prognostic factors with less impact on prognosis are the histological subtype, tumour size at diagnosis, age, gender and presence or absence of myasthenia gravis.
-The natural history of thymoma certainly illustrates the tendency for local mediastinal recurrence and pleural ‘‘droplet’’ recurrence presumably caused by mediastinal pleural invasion after resection. Local recurrences have been noted in the surgical incision used to completely remove a thymoma.
+==Risk Factors==
-====Diagnosis====
+* There are no established risk factors for thymoma.
-One-third of patients have their tumors discovered because they have an associated autoimmune disorder. The most common of those conditions is myasthenia gravis (MG); 10–15% of patients with MG have a thymoma and, conversely, 30–45% of patients with thymomas have MG.
-Historically, a classifiaction system used both histological features and clinical behavior. Masaoka staging is the clinically used staging system, although it may not be predictive for thymic carcinoma. GETT staging is the surgical staging system, and may have better correlation with outcome.
-Computed Tomography is the radiologic modality of choice to diagnose and evaluate thymoma.
-====Treatment====
-Surgery is the only curative treatment. Surgical biopsy should be avoided if a thymoma is highly suspecte based on clinical and radiological evaluation.The goal of surgery is complete resection of the tumor by total thymectomy and complete resection of the contiguous and noncontiguous disease. Chemo and radio therapy are used as adjuvant or neoadjuvant therapies. Sometimes they are used prior to surgery to make the tumor resectable. Signs and symptoms of myasthenia gravis should be evaluated before surgery and medically controlled.
-<gallery>
+==Natural History, Complication and Prognosis==
-Image:T008.png|MEDIASTINUM: ENCAPSULATED CYSTIC [[THYMOMA]]. Post-formalin-fixed cut surface reveals an ivory-colored tumor with multiple cystic spaces varying from pin-head sized to a few centimeters in diameter. Small hemorrhages are also noted.
+* If left untreated thymoma may progress to invade the [[mediastinum]] and the surrounding structure. Depending on the stage of the tumor at the time of diagnosis, the prognosis may vary.
-</gallery>
+* The prognosis is generally regarded as good.
+* Common complications of the thymoma include the pressure effect of the mass itself, [[autoimmune diseases]], and rarely, [[malignancy]].
+==Diagnosis==
+===History and symptoms===
+Symptoms of thymoma include
+* [[muscle weakness]]
+* [[cough]]
+* [[wheezing]]
+* [[dysphagia]].
+In addition to the symptoms of associated immune syndromes such as,
+* [[anemia]]
+* [[arthralgia]]
+* [[skin rash]].
+===Physical examination===
+Patients with thymoma usually appear asymptomatic. Physical examination of patients with thymoma is may be remarkable for,
+* Neck lump,
+* Facial [[swelling]]
+* [[wheezing]].
+===Staging===
+* Staging of thymic epithelial tumors was initially proposed by Bergh and his colleagues in 1978, modified by Wilkins and Castleman in 1979, and advanced by Masaoka et al. in 1981.
+* Modified Masaoka staging grouped with TNM classification is the most widely adopted system for thymic epithelial tumors currently in use.
+===Laboratory Findings===
+Laboratory findings associated with thymoma may include,
+* A[[antibodies|ntibodies]] to the [[acetylcholine receptor]],
+* Abnormal [[electrolyte]]s, [[renal]], and [[liver function]] tests.
+===X-Ray===
+* On chest x-ray, thymoma is characterized by oval to rounded, well demarcated, asymmetric, homogeneous mass of soft tissue density on one side of the midline.
+===CT Scan===
+* [[Computed Tomography]] scan may be diagnostic of thymoma. The tumor is generally located inside the thymus, and can be calcified.
+* Increased vascular enhancement can be indicative of malignancy, as can be pleural deposits.
+===MRI===
+* On [[thoracic]] MRI, thymoma is characterized by increased heterogenous signal on T2WI.
+===Ultrasound===
+* Ultrasound is used to guide [[fine needle aspiration]] or core [[needle biopsy]] in patients with thymoma.
+===Other Imaging Studies===
+* [[PET scan]] may be used in the diagnosis of thymoma.
+===Other Diagnostic Studies===
+Other diagnostic studies for Thymoma include
+* CT scan guided core needle [[biopsy]]
+* CT scan guided [[fine needle aspiration]]
+* [[mediastinoscopy]]
+* Videothoracoscopy.
+==Treatment==
+===Medical Therapy===
+* [[Chemotherapy]] and [[radiotherapy]] are used as [[adjuvant therapy|adjuvant]] or [[neoadjuvant therapy|neoadjuvant therapies]].
+* Neoadjuvant therpy may be administered prior to surgery to make the tumor resectable.
+===Surgery===
+* Surgery is the mainstay of treatment of thymoma.
+===Primary Prevention===
+* There are no primary preventive measures available for thymoma.
+===Secondary Prevention===
+* Complete surgical resection may help to prevent the recurrence of thymoma.
 ==References==
 {{Reflist|2}}
-[[Category:Oncology]]
 [[Category:Types of cancer]]
 [[Category:Rare diseases]]
 [[Category:Disease]]
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 {{WikiDoc Sources}}
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+[[Category:Oncology]]
+[[Category:Medicine]]
+[[Category:Hematology]]
+[[Category:Immunology]]
+[[Category:Surgery]]