Anterior%20Mediastinal%20Masses

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Anterior Mediastinal Masses

• November 30, 2004
• Neil J. Fernandes, M.D.

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Anatomy of the Mediastinum

• Boundaries
• Superior- Thoracic inlet
• Inferior- Diaphragm
• Anterior- Sternum
• Posterior- Vertebral bodies
• Lateral- Pleura

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Anatomy of the Mediastinum

• Compartments
• Anterosuperior anterior to the pericardium,
  extends superiorly to the thoracic inlet
• Middle bounded by the pericardium and the
  diaphragm
• Posterior pericardial reflection to the
  posterior border of the vertebral bodies,
  diaphragm to first rib

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Anatomy of the Mediastinum
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Anatomy of the Mediastinum

• Normal Contents
• Anterosuperior thymus, extrapericardial aorta
  and branches, IVC, SVC, lymphatic tissue
• Middle heart, intrapericardial great vessels,
  pulmonary hila, pericardium, trachea
• Posterior esophagus, vagus nerves, thoracic
  duct, sympathetic chain, descending thoracic
  aorta, azygous venous system

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Mediastinal Masses
Compartment Malignant
Anterosuperior 59
Middle 29
Posterior 16
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Anterosuperior Masses

• Thymus
• Mediastinal Lymphoma
• Germ Cell Tumor
• Thyroid/Parathyroid

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Thymus

• Thymoma
• Thymic carcinoma
• Thymic carcinoid
• Thymolipoma

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Thymoma

• Presentation
• Most common primary anterior mediastinal tumor
• MF, most gt40
• Most patients are asymptomatic
• Half of patients suffer have associated
  parathymic syndromes
• myasthenia gravis
• hypogammaglobulinemia
• pure red cell aplasia

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Thymoma

• Pathology
• Histologically benign lymphoepithelial neoplasms
• Solid, surrounded by a fibrous capsule
• Up to 1/3 have necrosis, hemorrhage or cysts
• Up to 1/3 are invasive into mediastinal fat,
  pleura, pericardium, great vessels, heart and
  lung
• Although they may seed the pleural space, pleural
  effusions are rare
• Lymphatic and hematogenous metastases are rare

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Thymoma

• Radiology
• Well-defined, rounded/lobular, mass arising from
  the thymus
• May give rise to pleural implants, rarely
  associated with effusions
• CT evaluation should evaluate the lung apices
  through the diaphragm to evaluate for vascular
  invasion and to rule out intrathoracic metastases

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Thymoma

• Treatment
• Complete surgical excision if possible
• Histologic evidence of tumor cells outside the
  capsule defines invasive thymoma
• XRT for incompletely resected or invasive tumor
• Chemotherapy has been attempted for metastatic or
  recurrent thymoma with cisplatin, doxorubicin and
  cyclophosphamide. In one study of 29 patients
  there were 3 CR, 12 PR and a median 5 year
  survival of 30

5 year survival 10 year survival
Encapsulated 75 63
Invasive 50 30
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Thymic Carcinoma

• Presentation
• MgtF, 40s
• Pathology
• Cytologic features of malignancy
• Early local invasion, widespread lymphatic and
  hematogenous metastases
• Radiology
• Large, poorly defined, infiltrative, associated
  with pleural and pericardial effusions
• Pleural implants are uncommon
• Treatment
• Etoposide/cisplatin XRT
• 5-year survival ranges from 15 to 90 depending
  on grade

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Thymic Carcinoid

• Presentation
• Men, 4th/5th decade
• Rarely associated with carcinoid syndrome
• Associated endocrine abnormalities Cushings
  syndrome due to ectopic ACTH or MEN
• 73 have regional lymph node and/or distant
  osteoblastic bone mets
• Pathology
• Histologically identical to carcinoid tumor at
  other sites
• Radiology
• Vascular, large, lobulated, invasive
• May have areas of hemorrhage and necrosis
• Punctate, dystrophic calcification
• Treatment
• Complete surgical excision
• Local invasion, mets to regional lymph nodes and
  distant mets have been treated with chemotherapy
  and XRT, but with poor results

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Thymolipoma

• Presentation
• MF, occurs over a wide age range, median age 27
• Most are asymptomatic
• Pathology
• Mature adipose cells and thymic tissue
• Radiology
• Large, soft, encapsulated
• May fall into the anteroinferior mediastinum
  mimicking cardiomegaly or elevated hemidiaphragm
• CT demonstrates a combination of fat and soft
  tissue densities within an encapsulated mass
• Treatment
• Surgical excision curative

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Anterosuperior Masses

• Thymus
• Thymoma
• Thymic carcinoma
• Thymic carcinoid
• Thymolipoma
• Mediastinal Lymphoma
• Germ Cell Tumor
• Thyroid/Parathyroid

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Primary Mediastinal Lymphoma

• 5-10 of patients with lymphoma present with
  primary mediastinal lesions
• Primary mediastinal lymphoma represents 10-20 of
  primary mediastinal masses in adults and are
  usually in the anterosuperior compartment
• Usually present with fever, weight loss and night
  sweats
• Pain, dyspnea, stridor, SVC syndrome due to mass
  effects are uncommon

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Primary Mediastinal Lymphoma

• Two Types
• Primary Mediastinal Hodgkins Lymphoma
• Primary Mediastinal Non-Hodgkins Lymphoma
• Poorly differentiated lymphoblastic
• Diffuse lymphocytic
• Primary Mediastinal B-cell Lymphoma

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Primary Mediastinal Hodgkins Lymphoma

• Presentation
• Incidental mediastinal mass on chest xray is the
  2nd most common presentation after asymptomatic
  lymphadenopathy
• Mass is usually large, rarely causes retrosternal
  chest pain, cough, dyspnea, effusions or SVC
  syndrome
• Bimodal age distribution maintained, however,
  first peak is larger in patients with mediastinal
  involvement
• B symptoms fever, weight loss (gt10 body wt in
  6 months), night sweats
• Generalized pruritus may precede the diagnosis by
  up to a year and, if severe, is a negative
  prognostic indicator
• EtOH-induced pain, most common in nodular
  sclerosing subtype

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Primary Mediastinal Hodgkins Lymphoma

• Radiology
• Multiple rounded masses (lymph nodes)
• Mediastinal nodal groups prevascular,
  aortopulmonary, paratracheal, pretracheal,
  subcarinal, posterior mediastinal
• Hilar nodes are considered separately
• Dominant mass (nodal coalescence)
• Thymic mass
• May be associated with infiltration and
  displacement of mediastinal structures and/or
  extranodal extension into the sternum, chest
  wall, pleura, pericardium or lung
• Usually homogenous attenuation on CT, but large
  masses may have necrosis, hemorrhage or cysts

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Modified Ann Arbor Staging for Hodgkins Lymphoma
Definition Treatment Cure
1 Single node region/lymphoid structure or extralymphatic site XRT gt90
2 2 node regions and/or extranodal organs on the same side of the diaphragm XRT 90
3 Node regions on both sides of the diaphragm and/or splenic involvement or contiguous involvement of an extranodal site Chemo XRT A 80-90 B 60-70
4 Diffuse or disseminated involvement of extranodal organs/tissues /- node involvement Chemo XRT 50-60
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Primary Mediastinal Non-Hodgkins
Lymphoma

• Lymphocytic Lymphoma
• Median age at presentation is 55, slight male
  predominance
• Advanced disease at presentation with
  constitutional symptoms, generalized
  lymphadenopathy /- extranodal disease

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Primary Mediastinal Non-Hodgkins
Lymphoma

• Lymphoblastic Lymphoma
• 1st/2nd decade, MgtF
• Aggressive, high grade
• Often present as a rapidly enlarging mediastinal
  mass which may cause compression of mediastinal
  contents
• Similar to ALL

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Primary Mediastinal Non-Hodgkins
Lymphoma

• Primary Mediastinal B-cell Lymphoma
• 3rd decade, FgtM
• Presents as a rapidly expanding mediastinal mass
  which may invade the airway, chest wall and/or
  adjacent structures.
• Extrathoracic involvement is uncommon
• Originally classified as a separate category due
  to its poor prognosis

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Anterosuperior Masses

• Thymus
• Thymoma
• Thymic carcinoma
• Thymic carcinoid
• Thymolipoma
• Mediastinal Lymphoma
• Hodgkins Lymphoma
• Non-Hodgkins Lymphoma
• Poorly differentiated lymphoblastic
• Diffuse lymphocytic
• Primary Mediastinal B-cell Lymphoma
• Germ Cell Tumor
• Thyroid/Parathyroid

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Mediastinal Germ Cell Tumors

• Represent 10-15 of adult anterosuperior
  mediastinal tumors
• Account for up to 10 of all germ cell tumors in
  men
• Arise from primordial germ cells which are
  displaced during embryogenesis as they migrate
  along the dorsal mesentery to the genital ridges
• Usually occur in young adults, median age 27

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Mediastinal Germ Cell Tumors

• Three types
• Teratoma
• Seminoma
• Nonseminomatous Germ Cell Tumor

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Mediastinal Teratomas

• Most common mediastinal germ cell tumor
• Three types
• Mature benign, well-differentiated
• Immature contains gt50 immature components, may
  recur or metastasize
• Malignant a mature teratoma that contains a
  focus of carcinoma, sarcoma or malignant GCT

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Mature Teratoma

• Occurs in children and young adults
• Usually asymptomatic, but if large enough, may
  cause chest pain, dyspnea, cough or other
  symptoms of mediastinal compression
• Contains derivatives of all three primitive germ
  layers including
• Ectoderm teeth, skin, hair
• Mesoderm cartilage and bone
• Endoderm bronchial, intestinal and pancreatic
  tissue
• Expectoration of hair (trichoptysis) is rare but
  pathognomonic
• Surgical excision is curative

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Mature Teratoma

• Radiology
• Large
• Rounded to lobulated, well-defined
• Protrude to one side
• 26 include calcifications
• On CT, multilocular/cystic with fluid, soft
  tissue, calcium and fat densities

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Immature Teratoma

• Rare
• Similar presentation to mature teratomas
• Composed of at least 2 out of 3 germinal layers
  and gt50 immature elements
• Treated with radical resection
• The roles of neoadjuvant and/or adjuvant
  chemotherapy are undefined

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Mediastinal Seminoma

• General
• Represents 40 of malignant mediastinal GCTs
• Afflicts Caucasian men in 20s-30s
• Only rarely represents a metastatic lesion from a
  testicular primary tumor, but testicular US is
  usually performed to rule this out
• If any other germ cell tumor histology is
  identified in the tumor, it is treated as a mixed
  NSGCT
• AFP normal, ?-HCG may be elevated in 10

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Mediastinal Seminoma

• Presentation
• Slow growing tumor, usually symptomatic at
  diagnosis
• Commonly presents with chest pain, dyspnea,
  cough, weight loss
• Presents infrequently with SVC syndrome
• Bulky, lobulated, homogeneous mass, no
  calcifications
• Usually not invasive, but many have metastasized
  to regional lymph nodes, lung and/or bone by the
  time of diagnosis

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Mediastinal Seminoma

• Treatment
• Chemo and XRT sensitive tumors
• Small tumors are treated with primary resection
  followed by XRT
• Advanced tumors are treated with XRT and/or four
  cycles of bleomycin, etoposide and cisplatin
• Treatment followed by surveillance of residual
  tumor lt 3 cm. or resection of residual tumor gt 3
  cm.
• Long-term survival is 60-80

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Mediastinal Nonseminomatous Germ Cell Tumors

• Five Types
• Embryonal cell carcinoma
• Endodermal sinus tumor elevated AFP
• Choriocarcinoma elevated ?-HCG
• Malignant Teratoma
• Mixed

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Mediastinal Nonseminomatous Germ Cell Tumors

• NSGCTs of the mediastinum have a worse prognosis
  than mediastinal seminomas or teratomas
• Occur in men in the 20-40 age group
• 20 of patients also have Klinefelters syndrome
• Also associated with i(12p)

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Mediastinal Nonseminomatous Germ Cell Tumors

• Associated with hematologic disorders, including,
• Megakaryoblastic leukemia
• Myelodysplasia
• Malignant mastocytosis
• Malignant histiocytosis
• Malignant hematologic cells often have the same
  i(12p) lesion identified in the mediastinal tumor
• Occasionally hematopoietic cells in the yolk sac
  portion of the tumor will have an
  immunohistochemical profile identical to
  malignant cells in the bone marrow

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Mediastinal Nonseminomatous Germ Cell Tumors

• Presentation
• Common symptoms at presentation include fever,
  chills, weight loss, chest pain, dyspnea, SVC
  syndrome
• Patients with choriocarcinoma and high levels of
  ?-hCG may have gynecomastia
• Most have elevated AFP and/or ?-hCG and the
  combination of elevated tumor markers in a young
  male with a mediastinal mass may be used as an
  indication to begin treatment, even prior to a
  pathologic diagnosis

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Mediastinal Nonseminomatous Germ Cell Tumors

• Radiology
• Large, irregular
• Extensive areas of heterogeneous low attenuation
  on CT due to necrosis, hemorrhage and/or cyst
  formation
• May invade the chest wall or adjacent structures
• Metastasizes to regional lymph nodes and distant
  sites
• Pleural and pericardial effusions are common

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Mediastinal Nonseminomatous Germ Cell Tumors

• Treatment
• Four cycles BEP (bleomycin, etoposide, cisplatin)
  /- XRT
• Residual masses are resected and two more cycles
  of chemotherapy given if malignant cells are
  found
• AFP and ?-hCG should be monitored to evaluate the
  effect of treatment and for recurrence

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Anterosuperior Masses

• Thymus
• Thymoma
• Thymic carcinoma
• Thymic carcinoid
• Thymolipoma
• Mediastinal Lymphoma
• Hodgkins Lymphoma
• Non-Hodgkins Lymphoma
• Poorly differentiated lymphoblastic
• Diffuse lymphocytic
• Primary Mediastinal B-cell Lymphoma

• Germ Cell Tumor
• Teratoma
• Mature
• Immature
• Seminoma
• Nonseminomatous Germ Cell
• Embryonal cell carcinoma
• Endodermal sinus tumor
• Choriocarcinoma
• Malignant teratoma
• Mixed
• Thyroid/Parathyroid

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Mediastinal Goiter

• A goiter is an enlargement of the thyroid gland
• The inferior poles of the thyroid normally lie
  superior to the thoracic inlet
• A minority of people may have thyroid glands that
  have descended to the level of the thoracic inlet
• Enlarging thyroid masses generally grow
  anteriorly as they are limited only by thin
  muscles, subcutaneous tissue and skin
• Growth through the thoracic inlet can produce
  symptoms related to compression of normal
  thoracic inlet contents

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Mediastinal Goiter

• The Thoracic Inlet
• 5x10 cm ovoid area
• Anterior Sternum
• Posterior T1 vertebral body
• Lateral First ribs
• Contains trachea, esophagus, carotid arteries,
  jugular veins, nerves

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Mediastinal Goiter

• Presentation
• Visible cervical goiter
• Dyspnea - exertional, positional, nocturnal. May
  have stridor if tracheal compression is severe
• Cough/Choking sensation
• Dysphagia - especially if goiter is posterior
• Hoarseness
• Diaphragmatic paralysis
• Horners syndrome
• Venous compression
• Hyperthyroidism - occurs in about 20, usually
  subclinical

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Mediastinal Goiter

• Physical Exam
• Visible cervical goiter - present in 77-90
• Inability to identify inferior pole of thyroid by
  palpation, even with neck hyperextension
• Tracheal deviation
• Pembertons maneuver
• Hold patients arms above head for 60 sec
• Positive test indicated by distended neck veins,
  facial plethora, cyanosis, inability to swallow,
  worsening of dyspnea or stridor
• May rarely result in impaction of goiter in
  thoracic inlet (Thyroid cork phenomenon)

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Mediastinal Goiter

• Diagnostic Studies
• Plain films
• May demonstrate tracheal narrowing and/or
  deviation with widening of the mediastinum
  superiorly
• Nuclear Medicine
• Radionuclide imaging with 123-I will help to
  define areas of autonomous functioning tissue
• May be misleading if mediastinal extension of the
  mass is hypofunctioning
• Pulmonary Function Tests
• Flow-volume loops demonstrate fixed upper airway
  obstruction
• Fine Needle Aspiration
• Indicated to evaluate for cancer if prominent
  discrete nodules are present or if there is a
  history of rapid growth, pain/tenderness, or
  firmness in one region

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Mediastinal Goiter

• Diagnostic Studies, cont.
• CT
• Encapsulated, lobular heterogeneous mass
• Heterogeneity is due to cysts, hemorrhage and
  locally elevated concentrations of iodine
• Coarse punctate or ring-like calcifications are
  common
• Useful to show continuity between the cervical
  and mediastinal portions of the mass
• CT is usually performed with the neck
  neutral/flexed. If the goiter extends lt1.5 cm
  below the sternal notch it may be completely
  cervical on extension and thus less likely to be
  the cause of the patients symptom
• If iodinated contrast is given, the patient
  should be pre-treated with methimazole or another
  anti-thyroid agent to reduce exacerbation of
  hyperthyroidism

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Mediastinal Goiter

• Pathology
• Most are benign
• Multinodular goiter and large follicular adenoma
  account for 95
• Large multinodular goiters have little
  functioning tissue. Usually have cystic
  degeneration, fibrosis, calcification, hemorrhage
• Many are found to have areas of papillary thyroid
  cancer

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Mediastinal Goiter

• Treatment
• Medical management of hyperthyroidism with
  antithyroid medications and ?-blocker
• Early surgical resection
• Most goiters continue to enlarge
• As patient ages surgical complications become
  more common
• Difficult to rule out malignancy in mediastinal
  portion of tumor
• Risk of hemorrhage into mass causing acute airway
  compression
• Resection can usually be performed through a
  single cervical incision, but massive tumors may
  require sternotomy

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Mediastinal Goiter

• Treatment, cont.
• Levothyroxine (suppressive dose)
• May reduce size of multinodular goiter over time
• Only helpful in patients who are euthyroid
• Patients with minimal mediastinal involvement, no
  compressive symptoms or patients who are poor
  surgical candidates may benefit
• Radioactive Iodine
• May be useful in patients who are poor surgical
  candidates, if mediastinal thyroid tissue is
  functional
• Radiation thyroiditis may worsen compressive
  symptoms

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Parathyroid Adenoma

• Accounts for 85 of primary hyperparathyroidism
• Occurs in middle-aged adults, 21 FM ratio
• Presents with
• Asymptomatic hypercalcemia
• Nephrolithiasis
• Bone pain
• Arthralgias/Myalgias
• Peptic ulcer disease
• Pancreatitis
• Fatigue/Anxiety/Depression

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Parathyroid Adenoma

• Embryology/Anatomy
• Superior parathyroids are derived from the 4th
  pharyngeal pouch and lie posterior to the upper
  poles of the thyroid
• Inferior parathyroids are derived from the 3rd
  pharyngeal pouch and usually lie near the lateral
  surface of the lower poles of the thyroid
• Up to 20 of patients have ectopic parathyroid
  glands
• The inferior parathyroids may lie anywhere along
  the path of descent of the thymus

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Parathyroid Adenoma

• Radiology
• Dual-phase 99mTc-sestamibi imaging
• The radiopharmaceutical is taken up within
  minutes of injection by both the thyroid and
  parathyroid glands.
• The rate of washout from normal thyroid tissue is
  much faster than the rate from parathyroid
  adenoma
• Early (10-15 min.) and Late (1.5-3 hr.) images of
  the neck and mediastinum are obtained and
  compared
• False-positives may occur with thyroid nodules or
  in parathyroid hyperplasia with one dominant
  gland
• False-negative studies can occur with very small
  lesions or abnormally rapid parathyroid washout

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Parathyroid Adenoma

• Treatment
• Surgical removal
• bilateral neck exploration
• unilateral neck exploration
• minimally invasive, image-guided
  parathyroidectomy
• US-guided EtOH ablation
• Embolization

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Anterosuperior Masses

• Thymus
• Thymoma
• Thymic carcinoma
• Thymic carcinoid
• Thymolipoma
• Mediastinal Lymphoma
• Hodgkins Lymphoma
• Non-Hodgkins Lymphoma
• Poorly differentiated lymphoblastic
• Diffuse lymphocytic
• Primary Mediastinal B-cell Lymphoma

• Germ Cell Tumor
• Teratoma
• Mature
• Immature
• Seminoma
• Nonseminomatous Germ Cell
• Embryonal cell carcinoma
• Endodermal sinus tumor
• Choriocarcinoma
• Malignant teratoma
• Mixed
• Thyroid/Parathyroid
• Goiter
• Parathyroid adenoma

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