thymoma a primary tumor of the thymus gland bradley j. phillips, md
TRANSCRIPT
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Thymoma
a primary tumor of the thymus gland
Bradley J. Phillips, MD
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Thymoma (1)
Prior to 1976, any tumor of the thymus gland was referred to as a “thymoma”
– true epithelial tumors
– thymic carcinoma
– seminoma
– lymphoma
• Rosai & Levine then defined the modern classification
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Thymoma (2)
• the functional unit of the thymus gland is the Lobule– composed of a cortex & medulla– epithelial cells– lymphocytes
thymomas are, by definition, primary tumors of benign-appearing thymic epithelial cells
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Thymoma (3)
• Given this definition, most thymomas are “benign”– the majority behave in an indolent fashion
– however, they can invade and metastasize (uncommon)
– when a thymoma is contained within the thymic capsule, it is referred to as “benign” or “noninvasive”
– when it penetrates through the capsule, it is referred to as “malignant” or “invasive”
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Thymoma (4)
thymic tumors composed of truly-malignant-appearing
epithelial cells are now referred to as
thymic carcinoma
• rare event
• accounts for less than 10 % of all primary thymic tumors
• locally aggressive & metastasize hematogenously
• poor overall prognosis
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Thymoma (5)
• 1985: revised histologic classification system
– based primarily on the relation of tumor histology
– not on the degree of cellular atypia
– confusing and unclear metabolic behavior
– controversial etiology & development
– vague natural history & unknown incidence
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Thymoma (6)
Some Points
Most large series from major referral centers report 100 - 200 patients over 25 - 30 yrs.
• Patients range from 8 months - 89 yrs of age
• Median age of presentation is 52 yrs.
• Thymomas occur equally in men & women
• Racial or ethnic predominance has not been recognized
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Thymoma (7)
“A Mass in the Anterior Mediastinum”
diagnostic studies: CXR & C.T. scan
– Thymomas Lipomas
– Teratomas Pericardial Cyst
– Thyroid tissue Morgagni Hernia
germ cell tumors (seminoma)
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Thymoma (8)
• Symptoms– Local Signs & Sx’s
• Due to invasion or compression of the mediastinum
• Hoarseness, cough, chest pain, dyspnea, & SVC-syndrome
• Usually due to advanced-stage disease
– Systemic Signs & Sx’s: the paraneoplastic syndromes• Appear early in the course of disease
• Myasthenia gravis / Red-cell aplasia / Aplastic anemia / Hypogammaglobunemia
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Thymoma (9)
the paraneoplastic syndromes are thought to be related to an autoimmune-phenomenon
• ~ 30 % of patients with Myasthenia have a thymoma
• role of thymectomy in Myasthenia is clear & convincing
however, this operation has NOT proven effective in treating the other forms
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Thymoma (10)
Staging
the most important factor in determining prognosis
is the tumor stage at time of operation,
which is best described by
macro-invasiveness by the surgeon of record
• Stage I, II, & IIb: macroscopically negative
• Stage III, IVa, & IVb: macroscopically-invasive
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Thymoma (11)
• Biopsy or “No-Biopsy”
– 85 % of patients will present with resectable disease and should proceed to extended thymectomy regardless of the biopsy result
– these patients should be taken to the operating room without a tissue diagnosis and undergo en-bloc resection
– patients with radiographic-unresectable disease may be candidates for open biopsy or core-biopsy
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Thymoma (12)
surgical resection
is the
mainstay of
treatment for thymoma
Following clinical stage, the most important determinant of recurrence is the
ability of the operating surgeon to achieve a complete resection
at the initial operation
• Extended-resection, 5-yr. Survival: 80 - 98 %
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Thymoma (13)
The Extended Thymectomy
a direct mediastinal approach to allow for the
en bloc removal of all cervical & mediastinal
soft tissue, including the thymus, mediastinal pleura,
adjacent perithymic fat, epiphrenic,
& perithyroidal tissue
• removes 95 - 98 % of all thymic tissue• based on Jaretzki’s study of thymic-origin
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Thymoma (14)
• Other Surgical Approaches– Transcervical Thymectomy– Video-assisted Thymectomy– Partial-mediastinal-debulking
• Operative mortality in most series is 0 - 1 %• Permanent injury to the Phrenic or Recurrent nerves: 1 %• Most common complications: arrythmias, residual ptx, effusions
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Thymoma (15)
• Other Modalities of Treatment
– Primary Radiotherapy: “unresectable tumor” / SVC-syndrome
– Adjuvant Radiotherapy: the standard of care for thymoma
• thymomas are well-known to be radiosensitive
• decreases recurrence by 5-fold across the board
– Chemotherapy: glucocorticoids & platinum-based agents
controversial / lack of long-term trials
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Thymoma (16)
Myasthenia Gravis
• 25,000 patients in the U.S. population• 2 - 80 yrs. of age (average age at surgery: 34 yrs)
• 2:1 female predominance• incidence of thymoma in M.G. pateints: 25 - 30 %• presents as progressive-generalized weakness
– eyes: ptosis / diplopia
– bulbar muscles: Dysphagia / dysarthria
– proximal limbs
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Thymoma (17)
“a deficiency of Ach-receptors (due to anti-AchR antibodies)
leads to a summarily-weakening of
end-plate potentials
and thus a progressive failure to generate muscle
contractures over time”
• First-line Tx: Medical– anticholinesterase agents: slow Ach breakdown– immunosuppressive agents: suppress antibody formation– plasmapheresis: removal of plasma-related factors
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Thymoma (18)
• Thymectomy & Myasthenia Gravis– The treatment of choice for all patients with generalized sx’s
– Preceded by medical stabilization & optimization
– Controversial with ocular-pt’s (15 %)
– The exact technical approach is dependent on preference
– Modified Osserman Classification• Classes I - V
• Following surgery, up to 96 % of pt’s will improve by 1-2 classes
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Thymoma (19)
What
is the
“Tensilon Test” ?
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Thymoma (20)
Who was
the first to report his
surgical experience with myasthenia gravis ?
clue: he removed a cystic mass from a young woman with myasthenia and she suddenly improved...
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Thymomas & Myasthenia Gravis
Questions ?