| What is the mediastinum and mediastinal lesions? | It is area between sternum, vertebra, and pleura
3 areas, anterior, middle-posterior and paravertebral
65% of lesions occur at anterior, 10% at middle posterior and 25% in paravertebral (adults)
In children, 38% anterior, 10% middle posterior and 52% posterior |
| What are the most common mediastinal lesions? | Intrathoracic hernia, goiter, thymic lesions, neurogenic neoplasms, lymphomas, cysts and germ cell neoplasms, lymphangioma, pancreatic pseudocyst, meningocele and extramedullary hematopoiesis (last 4 are less common)
Most frequent in adults: thymic, neurogenic neoplasms and foregut cysts
Most frequent in children: neurogenic neoplasms, foregut cysts and lymphoma.
Lung cancer and mediastinal lymph node metastasis may present as mediastinal lymphadenopathy
Sarcoidosis , silicosis and infectious lymphadenopathy are also possible. |
| How is the epidemiology of mediastinal diseases? | 1/3 of neoplasms are malignant, ones affecting children are more likely to be malignant than those affecting adults
Most masses (90%) are benign (asymptomatic), but 50% of symptomatic masses are malignant.
75% of pt with malignant neoplasms are symptomatic while less than 50% of ones with benign are symptomatic |
| What are the symptoms that occur for mediastinal masses? | constitutional symptoms, paraneoplastic syndromes and syndromes related to compression or invasion of adjacent mediastinal structures (which is seen in large locally invasive or malignant lesion) |
| How are patients with mediastinal disease evaluated? | Detailed hx and PE
PA and lateral X ray, CT, sometimes MRI and PET (using FDG) used for lesions and characterization usually followed by an invasive procedure for tissue diagnosis
Some mediastinal lesions are distinguished with radio, no need for biopsy (congenital cysts and vascular lesions)
Labs (CBC, electrolytes, renal and liver FT, serology (for autoantibodies)) |
| What is thymoma? | It is the most common mediastinal neoplasm in adults, most frequent tumor of anterior mediastinum.
Affects adults over 40
symptoms: cough, dyspnea, and chest pain (30% of pt), 40-70% have parathymic syndromes (Myasthenia gravis, hypogammaglobinemia, pure red cell aplasia and nonthymic malignancies)
Some are asymptomatic and seen incidentally, 85% of people with MG have thymic lymphoid hyperplasia and only 15% have thymoma.
However 30-50% of thymoma may have MG
10-15% have thymoma and hypogamma and pure red cell aplasia
12-20% have thymoma and thyroid/lung carcinoma |
| What is myasthenia gravis (MG)? | Rare autoimmune disorder caused by antibody mediated blockade of neuromuscular transmission in skeletal muscle weakness and rapid muscle fatigue.
It occurs when autoantibodies attack nicotinic Ah postsynaptic, and maybe other components of neuromuscular junction |
| How do thymoma present radiologically? | Rounded, well-circumscribed, unilateral anterior mediastinal mass.
Anterior to aortic root, anywhere from inlet to diaphragm and rarely in neck.
Homogenous, soft masses with heterogeneity due to cystic change/ hemorrhage/ necrosis. |
| How is drop metastasis of thymoma? | It goes to ipsilateral pleura/pericardium/ upper abdomen (through diaphragmic hiatus)
mediastinal invasion may be detected by CT (irregular tumoral surface, contralateral extension of thymoma across midline and invasion of mediastinal fat (MRI more sensitive for vascular invasion)
PET is useful for invasions
Guided needle biopsy used for dx (but may not be required before excision in classic thymoma) |
| Describe thymomas? | Neoplastic proliferation of thymic epithelia, intermixed with lymphocytes.
Staging based on presence of capsular invasion (seen macroscopic and confirmed microscopic)
Considered a malignant neoplasm in all stages have potential of metastasis, so directly resect
Post op radiation required for invasive thymoma (preop controversial)
Chemo with cisplatin regimen recommended for metastatic unresectable recurrent disease
Thymectomy tx of MG in absence of thymoma, but of parathymic syndrome it is controversial
Neurological improvement after thymectomy is less likely with MG ass with thymoma |
| What is thymic carcinoma? | Heterogenous aggressive epithelial malignancy with tendency of ealy local invasion and distant metastasis
Men more often affected (46 years)
malignant histologic features, large poorly defined, infiltrative, anterior mediastinal mass, regional lymph node and pulmonary metastases and pleural effusion |
| What are lymphomas mediastinal? | 10-20% of mediastinal neoplasms, 2/3 are non-hodgkins
Mediastinal involvement is usually systemic lymphoma, but may be primary disease (systemic is much more common than NHL and HL)
PET-CT assesses disease responsiveness to therapy and residual neoplasms |
| What is Hodgkin's disease? | Most often seen adults age 20-30, and older than 50
Same prevalance in both genders (except nodular sclerosis subtype more in women)
Presentation cervical and supraclavicular lymphadenopathy, less than 25% are limited only to thorax, 1/3 have systemic symptoms, generally asymptomatic although bulky lymphadenopathy may induce compression symptoms |
| What is the tx of lymphoma? | Chemotherapy |
