0424 - Mediastinal Tumours Flashcards
What is the mediastinum?
A central portion of the thorax that contains all thoracic structures except lungs and pleura. Divided into superior and inferior (anterior, middle, and posterior) compartments. Lymph nodes, small vessels, nerves, loose CT and adipose tissue in all compartments.
What are the contents of the superior portion of the mediastinum?
Thymus, thyroid, parathyroid Great vessels Oesophagus, trachea, thoracic duct.
What are the contents of the inferior posterior mediastinum?
Descending aorta, Inferior thoracic vertebrae Oesophagus Thoracic nerves
What are the contents of the inferior middle mediastinum?
Pericardium Heart Great vessels Phrenic nerves Main bronchi
What are the contents of the inferior anterior mediastinum?
In infancy contains the thymus. In adults smallest subdivision.
What is a good approach to analysing tumours?
Is it neoplastic or non-neoplastic? If neoplastic, is it benign/malignant? Primary/secondary? Cell type - epithelial, mesenchymal, mixed, lymphoid, melanocytic, Germ cell, unclassified. If non-neoplastic - infection/inflammation/deposit/hamartoma/congenital?
What is required in the macro description of a tumour
Site, size, shape, margins, capsule, colour, consistency 3 S’s, M, 3 C’s
What are three common tumours of the mediastinum?
Thymoma - Superior and inferior anterior Lymphoma - Superior and inferior middle/anterior Germ Cell tumours - inferior anterior
Describe the normal thymus under light microscopy
Divided into lobules by a fibrous septa/capsule around each one. Lobules contain cortex and medulla Cortex - basophilic lymphocytes (thymocyteS) Medulla - Epithelial cells and Hassall Corpuscles (round, keratinised whorls of epithelial cells). Increased fat with age.
Describe a thymoma
Taken to mean a neoplasm of thymic epithelial cells Adult >40yrs, M=F Found by myasthenia gravis (50% cases), local pressure symptoms, or incidental discovery Found on imaging, but biopsy required for diagnosis. Can invade local tissue, but not metastasise.
Describe the macro and micro appearance of a thymic epithelial neoplasm.
Macro - Encapsulated, lobulated pale cut surface with cystic change, calcification, and ossification. Micro - 3 components, fibrous tissue dividing into lobules, epithelial cells - too many, may be cytologically benign to malignant, lymphocytes are non-neoplastic,jsut immature T-cells.
What is the difference between thymoma and thymic carcinoma?
Both thymic epithelial neoplasms Thymoma is well differentiated, with no cellular atypia Thymic carcinoma is poorly differentiated with cellular features of malignancy. Thymic carcinoma can metastasize, but thymoma wont.
What is myasthenia gravis
Autoimmune disease attacking ACh receptors, leading to muscle weakness, fatigue, and death by respiratory failure. F>M 15% associated with thymoma, 65% with thymic hyperplasia.
What is non-Hodgkin lymphoma?
Neoplasm of a group of nodes, from indolent to aggressive.
85% from B cells, remainder T cells - all monoclonal.
Need systemic treatment due to lymphatic circulation
Lymph node tissue gets replaced by lymphoma nodules
What is Hodgkin lymphoma
Neoplasm of a single node or group of nodes according to staging.
Potentially curable - spreads in an orderly fashion.
Contains Reed-Sternberg “Owls Eye” cells.
Provide a definition of lymphoma and difference between Hodgkin and non-Hodgkin
Malignant tumour of lymphocytes occurring as a discrete tissue mass. Non-Hodgkin - B or T cells, 85% B. Systemic spread, so systemic treatment. Range of behaviour, but progressive disease Hodgkin - contains Reed-Sternberg cells. Orderly spread, so local treatment. Range of behaviour, but potentially curable.
How can you diagnose a lymphoma?
Requires Biopsy, then 3 paths to confirm.
- Morphology on H&E - node replaced by malignant follicles, loss of architecture and infiltration into fat.
- IHC - B Cells have CD20, T-cell CD3, Reed Sternberg (Hodgkins) - CD15 and CD30,
- Cytogenetics - Particularly t(14; 18), leading to over-expression of anti-apoptotic Bcl-2
Describe lymphoma in the mediastinum
Can be Hodgkin and non-Hodgkin - generally Hodgkin Can be primary mediastinal, or part of systemic disease Most commonly Hodgkin>Diffuse large cell lymphoma (B cell) >Lymphoblastic leukaemia (B or T cell).
Describe a germ cell tumour in the mediastinum
M>F. Broad age range but usually 10-30 yrs. Found in anterior superior mediastinum. Symptoms occure due to compression or invasion of structures. Can be teratomatous or non-teratomatous Non-teratomatous most aggressive.
What are the types of teratomatous and non-teratomatous mediastinal GCTs?
Teratomatous - mature (benign), immature (aggressive in adults) Non-teratomatous - Seminoma, yolk sac tumour, choriocarcinoma, embryonal carcinoma.
