Download Mediastinal Masses

Anterior Mediastinal Masses
November 30, 2004
Neil J. Fernandes, M.D.
Anatomy of the Mediastinum
Boundaries
Superior- Thoracic inlet
Inferior- Diaphragm
Anterior- Sternum
Posterior- Vertebral bodies
Lateral- Pleura
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
Anatomy of the Mediastinum
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
Mediastinal Masses
Compartment
% Malignant
Anterosuperior
59
Middle
29
Posterior
16
Anterosuperior Masses
Thymus
Mediastinal Lymphoma
Germ Cell Tumor
Thyroid/Parathyroid
Thymus
•
•
•
•
Thymoma
Thymic carcinoma
Thymic carcinoid
Thymolipoma
Thymoma
Presentation
• Most common primary anterior mediastinal tumor
• M=F, most >40
• Most patients are asymptomatic
• Half of patients suffer have associated parathymic
syndromes
• myasthenia gravis
• hypogammaglobulinemia
• pure red cell aplasia
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
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
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
5 year survival
10 year survival
Encapsulated
75%
63%
Invasive
50%
30%
• 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%
Thymic Carcinoma
Presentation
• M>F, 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
Thymic Carcinoid
Presentation
• Men, 4th/5th decade
• Rarely associated with carcinoid syndrome
• Associated endocrine abnormalities: Cushing’s 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
Thymolipoma
Presentation
• M=F, 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
Anterosuperior Masses
Thymus
•
•
•
•
Thymoma
Thymic carcinoma
Thymic carcinoid
Thymolipoma
Mediastinal Lymphoma
Germ Cell Tumor
Thyroid/Parathyroid
Primary Mediastinal Lymphoma
•
•
•
•
5-10% of patients with lymphoma present with
primary mediastinal lesions
Primary mediastinal lymphoma represents 1020% 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
Primary Mediastinal Lymphoma
Two Types
• Primary Mediastinal Hodgkin’s Lymphoma
• Primary Mediastinal Non-Hodgkin’s Lymphoma
•
•
Poorly differentiated lymphoblastic
Diffuse lymphocytic
•
Primary Mediastinal B-cell Lymphoma
Primary Mediastinal Hodgkin’s 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 (>10% 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
Primary Mediastinal Hodgkin’s 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
Modified Ann Arbor Staging for Hodgkin’s Lymphoma
Definition
Treatment
Cure
1
Single node region/lymphoid structure
or extralymphatic site
XRT
>90%
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%
Primary Mediastinal
Non-Hodgkin’s Lymphoma
Lymphocytic Lymphoma
• Median age at presentation is 55, slight
male predominance
• Advanced disease at presentation with
constitutional symptoms, generalized
lymphadenopathy +/- extranodal disease
Primary Mediastinal
Non-Hodgkin’s Lymphoma
Lymphoblastic Lymphoma
• 1st/2nd decade, M>F
• Aggressive, high grade
• Often present as a rapidly enlarging
mediastinal mass which may cause
compression of mediastinal contents
• Similar to ALL
Primary Mediastinal
Non-Hodgkin’s Lymphoma
Primary Mediastinal B-cell Lymphoma
• 3rd decade, F>M
• 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
Anterosuperior Masses
Thymus
•
•
•
•
Thymoma
Thymic carcinoma
Thymic carcinoid
Thymolipoma
Mediastinal Lymphoma
• Hodgkin’s Lymphoma
• Non-Hodgkin’s Lymphoma
• Poorly differentiated lymphoblastic
• Diffuse lymphocytic
• Primary Mediastinal B-cell Lymphoma
Germ Cell Tumor
Thyroid/Parathyroid
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
Mediastinal Germ Cell Tumors
Three types
• Teratoma
• Seminoma
• Nonseminomatous Germ Cell Tumor
Mediastinal Teratomas
• Most common mediastinal germ cell tumor
• Three types:
• Mature: benign, well-differentiated
• Immature: contains >50% immature
components, may recur or metastasize
• Malignant: a mature teratoma that contains a
focus of carcinoma, sarcoma or malignant GCT
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
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
Immature Teratoma
• Rare
• Similar presentation to mature teratomas
• Composed of at least 2 out of 3 germinal
layers and >50% immature elements
• Treated with radical resection
• The roles of neoadjuvant and/or adjuvant
chemotherapy are undefined
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%
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
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 < 3 cm. or resection of residual tumor > 3
cm.
• Long-term survival is 60-80%
Mediastinal Nonseminomatous
Germ Cell Tumors
• Five Types
•
•
•
•
•
Embryonal cell carcinoma
Endodermal sinus tumor: elevated AFP
Choriocarcinoma: elevated -HCG
Malignant Teratoma
Mixed
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 Klinefelter’s
syndrome
• Also associated with i(12p)
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
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
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
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
Anterosuperior Masses
Thymus
Germ Cell Tumor
•
•
•
•
• Teratoma
Thymoma
Thymic carcinoma
Thymic carcinoid
Thymolipoma
Mediastinal Lymphoma
• Hodgkin’s Lymphoma
• Non-Hodgkin’s Lymphoma
• Poorly differentiated lymphoblastic
• Diffuse lymphocytic
• Primary Mediastinal B-cell
Lymphoma
• Mature
• Immature
• Seminoma
• Nonseminomatous Germ Cell
•
•
•
•
•
Embryonal cell carcinoma
Endodermal sinus tumor
Choriocarcinoma
Malignant teratoma
Mixed
Thyroid/Parathyroid
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
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
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
• Horner’s syndrome
• Venous compression
• Hyperthyroidism - occurs in about 20%, usually
subclinical
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
• Pemberton’s maneuver
• Hold patient’s 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)
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
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 <1.5 cm below the sternal notch it
may be completely cervical on extension and thus less
likely to be the cause of the patient’s symptom
• If iodinated contrast is given, the patient should be pretreated with methimazole or another anti-thyroid agent
to reduce exacerbation of hyperthyroidism
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
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
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
Parathyroid Adenoma
• Accounts for 85% of primary hyperparathyroidism
• Occurs in middle-aged adults, 2:1 F:M ratio
• Presents with
•
•
•
•
•
•
•
Asymptomatic hypercalcemia
Nephrolithiasis
Bone pain
Arthralgias/Myalgias
Peptic ulcer disease
Pancreatitis
Fatigue/Anxiety/Depression
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
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
Parathyroid Adenoma
Treatment
• Surgical removal
• bilateral neck exploration
• unilateral neck exploration
• minimally invasive, image-guided parathyroidectomy
• US-guided EtOH ablation
• Embolization
Anterosuperior Masses
Thymus
Germ Cell Tumor
•
•
•
•
• Teratoma
Thymoma
Thymic carcinoma
Thymic carcinoid
Thymolipoma
Mediastinal Lymphoma
• Hodgkin’s Lymphoma
• Non-Hodgkin’s Lymphoma
• Poorly differentiated lymphoblastic
• Diffuse lymphocytic
• Primary Mediastinal B-cell
Lymphoma
• 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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