Evaluation of Mediastinal Mass

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Evaluation of Mediastinal Mass

• Leslie Proctor, M.D.
• November 21, 2008

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Mediastinal Anatomy

• Includes structures bound by
• the thoracic inlet
• diaphragm
• sternum
• vertebral bodies
• and pleura

• Has 3 compartments
• Anterior
• Middle
• Posterior

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The differential diagnosis of a mediastinal mass
depends upon the anatomic compartment in which it
arises. Redrawn from Baue, AE, et al. Glenn's
Thoracic and Cardiovascular Surgery. 5th ed.
Appleton Lange, Norwalk, CT, 1991.
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Mediastinal Anatomy

• Middle Compartment is bounded by

• Anterior Compartment includes

• The pericardium anteriorly
• The posterior pericardial reflection
• The diaphragm
• The thoracic inlet.
• This compartment includes the heart,
  intrapericardial great vessels, pericardium, and
  trachea.

• Thymus
• Extrapericardial aorta and its branches
• The great veins
• Lymphatic tissue.

Posterior Compartment

• Extends from the posterior pericardial
  reflection to the posterior border of the
  vertebral bodies and from the first rib to the
  diaphragm.
• It includes the esophagus, vagus nerves,
  thoracic duct, sympathetic chain, and azygous
  venous system

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Anatomic Distribution of Masses

• Anterior Mediastinum

• Thymoma

• Thymic tumors and cysts
• Germ cell tumors
• Lymphomas
• Intrathoracic goiter and thyroid tumors
• Parathyroid adenomas
• Connective tissue tumors
• lipomas and liposarcomas
• lymphangiomas
• hemangiomas

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Anatomic Distribution of Masses

• Middle Mediastinum

• Retrosternal Goiter

• Thyroid tumor or goiter
• Tracheal tumors
• Aortopulmonary paraganglioma
• paracardial cysts
• bronchogenic cysts
• lymphoma
• Lymphadenopathy

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Anatomic Distribution of Masses

• Posterior Mediastinum

• Paraspinal Ganglioneuroma

• Neurogenic tumors
• including Schwannomas
• Esophageal tumors
• Hiatal Hernias
• Neurenteric Cysts
• And rarely
• extramedullary hematopoiesis
• pancreatic pseudocyst
• achalasia

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About Neurogenic tumors

• 9 to 39 percent of all mediastinal tumors
• develop from mediastinal peripheral nerves,
  sympathetic and parasympathetic ganglia, and
  embryonic remnants of the neural tube.
• most frequent in the posterior compartment of the
  mediastinum
• Can cause neurologic symptoms by compression.
• Benign Schwannoma is most common
• often asymptomatic, but can be associated with
  Horners or Pancoasts syndrome
• Focal calcifications and cystic changes
• can extend through an intervertebral foramen,
  resulting in dumbbell-shaped tumors, and
  neurologic symptoms of spinal cord compression
• Gross Histology
• encapsulated, solid, soft, yellow-pink nodule,
  with the capsule attached to the epineurium of
  the nerve that gives rise to the neoplasm
• Microscopic histology
• composed of spindle cells with elongated nuclei,
  forming interlacing bundles with focal nuclear
  palisading
• nuclear atypia, and stromal sclerosis in older
  lesions
• Mitotic figures are rare.
• Immunohistochemical studies reveal a strongly
  positive reaction with S-100 protein.

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Mediastinal Benign Schwannoma
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Anatomic Distribution of Masses

• A mass may extend beyond these boundaries as it
  grows in size
• In adults, anterior compartment masses are more
  likely to be malignant

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Age Distribution

• Age can help predict etiology of the mass
• infants and children, neurogenic tumors and
  enterogenous cysts are the most common
  mediastinal masses
• In adults, neurogenic tumors, thymomas, and
  thymic cysts are most frequently encountered
  lesions
• In 20-40 year olds, the likelihood of a mass
  being malignant is greater secondary to the
  increased incidence of lymphoma (Hodgkins and
  non-Hodgkin's) and germ cell tumors

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Signs and Symptoms

• Depend on location of mass
• Asymptomatic
• Vague symptoms
• aching pain
• cough
• Children more likely to be symptomatic
• respiratory difficulty
• recurrent pulmonary infections

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Signs and Symptoms

• Airway compression
• recurrent pulmonary infection
• hemoptysis
• Esophageal compression
• dysphagia
• Involvement of the spinal column
• paralysis
• Phrenic nerve damage
• elevated hemidiaphragm

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Signs and Symptoms

• Recurrent laryngeal nerve involvement
• Hoarseness
• Sympathetic ganglion involvement
• Horners Syndrome
• Ptosis, miosis, anhidrosis
• superior vena cava involvement
• Superior vena cava syndrome
• facial neck, and UE swelling, dyspnea, chest and
  UE pain, mental status changes

Horners Syndrome
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Signs and Symptoms

• Can also be associated with systemic diseases
• Thymoma myasthenia gravis, immune deficiency,
  red cell aplastic anemia
• Goiter thyroxicosis
• Thymic carcinoid Cushings syndrome
• Parathyroid hyperparathyroidism

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Evaluation Imaging

• 2 view PA/Lat Chest X-ray
• comparisons with old x-rays important
• Chest CT with contrast
• most important method of evaluation
• Can help determine location, morphology, size,
  and attenutation coefficient
• Important for directing further therapy
• MRI
• when contrast allergy or renal failure present
• when vascular or chest wall involvement is
  suspected
• neurogenic tumors (especially helpful in
  detecting intraspinal component
• Ultrasound
• Differentiate cystic from solid masses and relate
  to surrounding structures
• When mass is close to heart or pericardium
• Transesophageal or transbronchial useful to
  evaluate lymph nodes, sometimes for biopsy
• Radio nucleotide scanning
• With radioactive iodine when thyroid tumor
  suspected
• PET scanning
• Can localize specific tumors (pheochromocytoma,
  paragangliomas, neuroblastomas, neurogangliomas
  by targeting their metabolic pathways

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Evaluation Laboratory

• Depends on clinic setting, but may include
• Thyroid function tests
• If goiter suspected
• Chemistry panel including calcium and phosphate
  and PTH
• If parathyroid adenoma suspected
• Fractionated 24-hour urinary metanephrines and
  catecholamines
• If paraganglionic tumor suspected
• AFP/beta HCG
• In all males with anterior mediastinal tumor
  because of concern for non-seminomatous germ cell
  tumor

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Management

• Tailored to specific or likely diagnosis
• Must decide whether to excise, biopsy, or
  aspirate lesion
• Excision should be done with teratomas, thymomas,
  and isolated masses likely to be benign (VATS,
  median sternotomy, thoracotomy)
• Needle aspiration of cystic lesions
• Diagnostic biopsy is procedure of choice when
  suspect lymphoma, germ cell tumor, or
  unresectable invasive malignancy

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References

• Kallab, Andre MD. Superior Vena Cava Syndrome.
  Emedicine. August 10 2005. http//www.emedicine.c
  om/MED/topic2208.htm
• Gangadharan, Sidhu MD. Evaluation of Mediastinal
  Masses. UptoDate. October 7, 2008.
• Parmar, Malvinder S, MB, MS. Horners Syndrome.
  Emedicine. June 5, 2008. http//www.emedicine.com
  /med/TOPIC1029.HTML
• Strolls, DC, Rosado-de-Christenson, ML, Jett, JR.
  Primary mediastinal tumors. Part I Tumors of the
  anterior mediastinum. Chest 1997 112511.
• Strollo, DC, Rosado-de-Christenson, ML, Jett, JR.
  Primary mediastinal tumors Part II. Tumors of
  the middle and posterior mediastinum. Chest 1997
  1121344.
• Medscape.com (multiple images)
• Devouassoux-Shisheboran, Mojgan MD and Travis,
  William D MD. Pathology of Mediastnal Tumors.
  Uptodate. September 9th, 2008.