THYMIC TUMORS

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THYMIC TUMORS

• GENERAL THORACIC SURGERY
• CHAPTER 167

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Thymic tumor

• Almost in the anterior mediastinum.
• Secondary to neurogenic tumor in mediastinal
  tumor.
• Rare in children younger than 16 y/o.

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Thymic tumor

• Separated into three histologic categories
• Thymoma.
• Thymic carcinoma.
• Neuroendocrine tumor.

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THYMOMA
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Location

• 95 in anterior mediastinum.
• Neck.
• Left hilar region.
• Within lung parenchynma.
• Anterior cardiophrenic angle.

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Pathology

• All thymoma derive from thymic epithelial cell.
• Predominantly lymphocytic thymoma (more than 66
  lymphocyte).
• Predominantly epithelial thymoma (more than 66
  epithelial cell).
• Mixed lymphoepithelial thymoma.
• Spindle cell tumor.

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Pathology

• Most important gross feature The presence or
  absence of encapsulation of tumor and the gross
  invasion into adjacent structure.
• The invasion present The thymoma must be
  considered malignant lesion regardless the
  microscopic appearance.
• Extensive spread.
• Incidence of distal metastasis is 3.
• Stage.

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Another class

• Cortical.
• Medullary.
• Mixed thymoma.
• Immunohistochemistry.

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Clinical presentation

• 50-60 y/o.
• Sex distribution Equal.
• s/s chest pain, SOB, cough, SVC syndrome,
  paralysis of hemidiaphragm, hoarseness, weight
  loss, fatigue, fever, night sweats.

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Parathymic syndrome

• 40 with parathymic syndrome.
• Myasthenia gravis.
• Pure red cell aplasia.
• Immunoglobulin deficiency.
• Systemic lupus erythematosusinfrequently, 2.5,
  poor prognosis.
• Nonthymic cancer17-21.
• Inappropriate antidiuretic hormone
  secretion(SIADH)-- rarely, malignant thymoma and
  spindle cell thymoma.

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Myasthenia gravis

• Most commonly associated disease.
• 30 of patient with thymoma associate with MG.
• Only 5-15 patient with MG have thymoma.
• 10-15 older than patient with MG without tumor,
  younger than patient with thymoma without MG.
• Any type of thymoma except spindle type, marked
  associated squamous elements in thymus.
• Little affect on local presention, clinical
  behavior, prognosis.
• Better prognosis than patient with thymoma
  without MG.

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Pure red cell aplasia

• Anemia.
• Suppression erythrogenesis in bone marrow.
• Mechanism--Not clear, IgG antibodies inhibit
  erythropoietin or hemoglobin synthesis, cytotoxic
  to erythroblast, decrease B cell.
• 50 patients with red cell aplasia have thymoma,
  5 thymoma with red cell aplasia.
• Most (70)are non-invasive spindle cell.
• 25-33 patient with red cell aplasia benefit from
  excision of the thymoma.

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Immunoglobulin deficiency

• Spindle cell type.
• Acquired hypogammaglobulinemia.
• Suppressor T-cell inhibiting immunoglobulin
  synthesis.

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Diagnostic studies

• Standard posteroanterior and lateral chest
  radiographies.
• CXRSmooth or lobulated mas, right side the
  silhouette sign present, left side the sign
  abscent.
• Calcification 10.
• CTDelineate the extent of mass, cannot not
  differentiating benign and malignant, assessing
  intrathoracic spread of an invasive thymoma.

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Surgical biopsy

• Unnecessary for a suspected locally symptomatic
  thymoma, because the capsule of tumor may be
  violated by invasive procedure.
• Only distinguish the tumor from the other
  malignant tumor, or locally symptomatic, clearly
  nonresectable, biopsy is to establish the
  diagnosis before making decision of therapy.
• Fine needle biopsy by CT or sono-guide.
• Extend substernal mediastinoscopy.
• Anterior mediastinotomy.
• Lateral thoracotomy.
• VATS.

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Treatment

• Depend on clinical presentation.
• Surgical resection thymoma is encapsulated and
  free from adjacent structure.
• Radiation in atage II, III.
• chemotherapy in locally nonresectable, presence
  distal metastasis, neoadjuvant therapy for
  initially advanced local diasease or in locally
  recurrent disease.

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Surgical excision

• All patient with thymoma should undergo as
  complete resection as possible.
• Pulmonary lesion should be excised at the same
  time.
• Tumor encapsulated total thymectomy.
• Simple enucleation is avoid except the unusual
  condition(excision through lateral thoracotomy
  with unknown preoperative diagnosis).

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Surgical excision

• Preferred median sternotomy.
• Posterolateral thoracotomy for large tumor in
  hemithorax or tumor from anterior cardiophrenic
  angle.
• Bilateral anterior fourth intercostals
  incisionwith transverse section of sternum
  (clamshell) for large midline tumors.
• The use of video-assisted thoracoscopic removal
  of thymoma is unacceptable even for stage I
  tumor.

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Surgical excision

• Extend procedure the entire thymus and adjacent
  fat should be removed if possible.
• Tumor fixation to nonvital adjacent structure
  should be resect(pleura, lung, pericardium, ).

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Surgical excision

• One phrenic nerve involve could be resected if
  patient could tolerate loss of hemidiaphragm
  function.
• If both phrenic are involved, only debulking is
  performed.

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Surgical excision

• The wall of SVC involve if no SVC syndrome,
  lateral wall resection of SVC and replace graft.
• When the aorta, major pulmonary vessels,
  recurrent nerve trachea, are involve, only
  debulking.
• Operative mortality 3.1-7.7.

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Radiation therapy

• For invasive thymoma.
• In stage I is uncertain.
• For resected stage II or completely or
  incompletely resected stage III disease.
• 4500-5000 cGy for suspected microscopic residual
  disease.
• 6000 cGy for known residual disease.
• Brachytherapy with I-125 seed placed in gross
  residual disease at time of operation.

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Chemotherapy

• For stage III and IV.
• Cisplatin, doxorubucin, vincristine,
  cyclophosphamide, neoadjuvant.

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Treatment of recurrent local disease or distant
metastases

• Recurrent I 0-5, II 10, III 30, IVa
  33.
• Second resection if possible.
• 5-year survival is 65.
• For stage III recurrent irradiation or
  chemotherapy.

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Survival

• Depend on stage, tumor size, histology, extent
  of resection.
• Better in patient with thymoma associated with
  MG.
• Poor in patient with red cell aplasia,
  hypogammaglobulinemia, SLE.

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Thymic carcinoma

• Low and high grade.
• Malignant cytologic and architectural feature.
• Staging not standardized.

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Squamous cell carcinoma

• Most common.
• Men predominant.
• 60 y/o.
• Partially encapsulated.
• s/s weight loss, chest pain, cough, hemoptysis.
  
• TreatmentSurgical resection, sensitive to
  radiation, combination chemotherapy.
• Prognosis excellent in well-differentiated
  squamous cell carcnoma.

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Lymphoepitheliomalike carcinoma

• Epstein-Barr virus.
• Treatmentirradiation therapy, chemotherapy.

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Tumor of neuroendocrine cell origin

• Thymic carcinoid tumor.
• Small cell carcinoma.

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Thymic carcinoid tumor

• Large.
• One-half lesion infiltrative into adjacent
  structures.
• Associated Cushings syndrome.
• 3/4 are men.
• Mean age 42 y/o.
• s/s asymptomatic, chest pain, cough dyspnea,
  SVC syndrome, fatigue fever, night sweat.

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Thymic carcinoid tumor

• 1/3 have feature of Cushing sundrome ectopic
  ACTH production.
• 15-18 with multiple endocrine neoplasia(MEN)syndr
  ome.
• Most MEN I.
• Few MEN II.
• Thymic carcinoid associated with MEN syndrome is
  more malignant in behavior.
• 1/3 with bone metastases.

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Multiple endocrine neoplasia(MEN)

• MEN I(Werner syndrome) Single or multiple
  parathyroid adenoma, islet cell tumor of
  pancrease, adrenal neoplasm, thyroid adenoma,
  multiple lipoma.
• MEN II(Sipple syndrome)Thyroid medullary
  carcinoma, pheochronocytoma, parathyroid
  neoplasia.

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Thymic carcinoid tumor

• Treatmentcomplete surgical resction or debulking
  tumor, radiation therapy.
• 73 local recurrence or metastases.
• Overall cure rate is low 13.
• Mean survival of metastases disease is 3 years.

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Small (Oat)cell carcinoma

• Aggressive and metastases extensively,
• Associated with MEN I.
• Treatmentradiation therapy and chemotherapy.