Mediastinal Masses Flashcards
Masses of Anterior/Superior Mediastinal Compartment
- Thymic neoplasm (thymoma, thymic carcinoma, carinoid)
- Lymphoma
- Germ cell tumors (teratoma, seminoma, non-seminoma tumor)
- Thyroid adenoma
- Parathyroid adenoma
Masses of Middle Mediastinal Compartment
- Bronchogenic cyst
- Pericardial cyst
- Enteric cyst
- Lymphoma
Masses of Posterior Mediastinal Compartment
- Neurogenic tumors
- Esophageal/Enteric cyst
- Lymphoma
Clinical presentation of mediastinal masses
- Asymptomatic and incidental (MC)
- Chest pain
- Cough
- Dyspnea
- Pain and Neurologic deficit (neurogenic tumor)
Diagnostic study of choice for mediastinal tumors
CT scan
(location, morphology, relationship to other structures)
Diagnostic approach to small (<5cm) tumors with characteristic features (i.e. thymoma, teratoma, benign cyst)
Surgical resection
Diagnostic approach to large mediastinal tumors
- CT-guided percutaneous biopsy
- Open biopsy
- Cervical mediastinoscopy
- VATS
- Chamberlain mediastinoscopy
- Thoracotomy
Serum tumor markers that much be checked for mediastinal masses (anterior)
- Beta-HCG
- AFP
- LDH
Diagnostic algorithm for anterior mediastinal masses
- CXR
- Chest CT
- Tissue biopsy (percutaneous vs. open)
- Serum tumor markers (Beta-HCG, AFP, LDH)
Tumors are most common in what mediastinal compartment
Anterior compartment
95% of all anterior mediastinal compartment tumors include:
- Four “Ts”
- Thymoma (MC)
- Teratoma (germ cell tumor)
- “Terrible” lymphoma
- Thyroid goiter
MC anterior mediastinal tumor
Thymoma
Clinical presentation of thymoma
- M:F (1:1)
- 30-50 years old
- 50% = asymptomatic/incidental
- 50% = symptomatic (pain, dyspnea, cough, horseness)
Thymoma associated syndromes
- Myasthenia gravis
- Red cell hypoplasia
- Hypogammaglobulinemia
- SLE
- Rheumatoid arthritis
- UC
- Thyroiditis
CT characteristics of benign thymoma
- < 5 cm
- round
- well-circumscribed
CT characteristics of malignant thymoma
- > 5 cm
- Irregular shape
- Invade neighboring structures
Treatment of choice for all thymoma
- Complete excision
- En bloc resection
- Pleura
- Pericardium
- Innominate vein
- SVC
- Lung
- Can excise one phrenic nerve and dissect tumor off other
- En bloc resection
Thymoma
Definition of surgically resectable
Surgery is indicated as the initial treatment for patients in whom a complete, R0 resection is considered feasible, ie, those with
- Completely encapsulated tumors or
- those with tumors invading readily resectable structures, such as the mediastinal pleura, pericardium, or adjacent lung.
Treatment of Stage I and Stage II Thymoma
Treatment of stage I and stage II thymoma is surgery, which may be followed by radiation therapy.
Treatment of stage III and stage IV thymoma that may be completely removed by surgery
Surgery followed by radiation therapy.
Neoadjuvant chemotherapy followed by surgery and radiation therapy.
Treatment of stage III and stage IV thymoma that cannot be completely removed by surgery
Chemotherapy.
Chemotherapy followed by radiation therapy.
Neoadjuvant chemotherapy followed by surgery (if operable) and radiation therapy.
Thymoma
Indications for Postoperative radiation therapy
*Stage I thymoma (Masaoka stage I to II)
-For patients with no capsular invasion, we offer observation given the low risk of recurrence and lack of overall survival benefit with postoperative RT (PORT). Such patients should be followed with annual imaging of the chest (computed tomography [CT]/magnetic resonance imaging [MRI]) for a minimum of ten years due to the risk of late recurrences. (See ‘Surveillance after treatment’ below.)
-For patients with invasion into the mediastinal fat or pleura and microscopic or grossly positive surgical margins, we suggest the addition of PORT, as this approach reduces the risk of recurrence to that of patients with R0 resections and lower-risk features. However, observation is an appropriate alternative given limited data. (See ‘Surveillance after treatment’ below.)
*Stage II to III thymoma (Masaoka stage III) – PORT is indicated in such patients given a higher risk of local recurrence.
*Stage IV thymoma (Masaoka stage IV) – RT should be individualized to the needs of the patient. RT can be used for palliation and possibly as curative therapy in oligometastatic disease.
MC surgical exposure/approachs for thymectomy
Median sternotomy
Cervical
VATS
Thymoma Staging (5-Yr Survival)
Survival based on Stage
- Stage I (95%)
- completely encapsulated
- Stage II (85%)
- IIa: mediastinal fat/pleura
- IIb: through capsule
- Stage III (70%)
- direct invasion of adjacent organ
- Stage IV (50%)
- IVa: pleura/pericardium mets
- IVb: distant mets
Thymoma
Indications for neoadjuvant/adjuvant therapy
Stage III-IV disease
Chemotherapy is offered in the neoadjuvant setting for those with potentially resectable thymoma or thymic carcinoma, or as primary therapy (with or without RT) for those with unresectable thymoma or thymic carcinoma.
Thymoma
Neoadjuvant/Adjuvant therapy regimen
Cisplatin-based chemotherapy + XRT
Mechanism of action of Myasthenia Gravis
Autoantibodies to ACh receptor
(decreased transmission of AP at the NM junction)
Demographics of Myasthenia Gravis
- 2x MC in women
- 2-3rd decade of life
Myasthenia Gravis Symptoms Grades
- Grade I: focal disease-ocular muscle weakness
- Grade II: Mild-moderate generalized disease
- Grade III: Severe generalized disease
- Grade IV: life-threatening weakness - respiratory failure
Confirmatory tests for Myasthenia Gravis
Endrophonium (short acting anticholinesterase ) test
ACh Receptor assay
Medical treatment for Myasthenia Gravis
Pryidostigmine (long-acting anticholinesterase)
Plasmapheresis and IVIg
Preop Mgmt for the patient with myasthenia gravis: Anticholinesterase agent
- We suggest continuing anticholinesterase agents (ie, pyridostigmine or neostigmine) up to and including the morning of surgery.
*
Preop Mgmt for the patient with myasthenia gravis: Immunomodulating therapy
- In the occasional patient with persistent mild residual respiratory impairment or dysphagia despite treatment with pyridostigmine and immunotherapy (eg, glucocorticoids), we administer a course of IVIG (2 grams/kg over two to five days) or plasmapheresis (three to five exchanges over 7 to 14 days) preoperatively.
- This practice is empiric, with a goal of reducing the risk of a postoperative flare evolving quickly into myasthenic crisis.
*** Treatment should be timed to end the week prior to surgery so that the effects of the rapid therapy peak and persist through the perioperative period. **
Myasthenia Gravis
Induction and maintenance of anesthesia
- NMBAs should be avoided when possible.
- If NMBAs are necessary, we suggest the use of rocuronium or vecuronium, and then reversal with sugammadex.
Myasthenia Gravis
Response to Depolarizing neuromuscular blocking agents
Patients with MG are resistant to neuromuscular blockade with depolarizing NMBAs (eg, succinylcholine), possibly because they have a decreased number of acetylcholine receptors [27,28]. T
Myasthenia Gravis
Response to Nondepolarizing neuromuscular blocking agents
Patients with MG are extremely sensitive to nondepolarizing NMBAs (eg, rocuronium, vecuronium, cisatracurium). Very small doses and residual drug effect may result in respiratory distress or loss of airway protection after emergence from anesthesia.