Primary Mediastinal B Cell Lymphoma Flashcards
From which cells does Primary Mediastinal B Cell LYmphoma arise from?
Thymic (Medullary) B cells
Has features distinct from DLBCL
Shares some clinical + Biologic features with classical Nodular sclerosing Hodgkin Lymphoma
How frequent is PMBL?
7% of DLBCL
2.4% of all NHL
What is the epidemiology of PMBL?
7% of DLBCL
2.4% of all NHL
Female
Median age 30-40 yo
What are some features of SVCO?
Usually a/w the compression/invasion of the structures around.
Think:
- Trachea - airway compromise
- Heart - pericardial effusion/tamponade
- lungs/pleura - SOB/cough/dyspnoea/pleural effusion
- blood vessels - SVCO
Frequently with airway compromise Dyspnoea Facial swelling/head fullness exacerbated by bending forward or lying down Arm swelling Cough Chest pain Dysphagia Headaches/confusion/coma Hoarseness
What are the potential oncological emergencies that can occur with PMBL?
SVCO Acute airway obstruction Pericardial tamponade Hyperuricemia and TLS Thrombosis of major neck/superior thoracic veins
What is tumor lysis syndrome?
Oncological emergency that is caused by massive tumor cell lysis and the release of large amounts of potassium, phosphate and Uric acid into the systemic circulation.
THe deposition of Uric acid and/or Ca Phosphate crystals in the renal tubules can cause ARF (which is usu anuric)
What is the morphology in PMBL?
Large cells with variable nuclear features resembling centroblasts, large centrocytes or multilobulated cells, often with pale/clear cytoplasm.
Sometimes resemble immuoblasts.
RS cells may be present
Many with fine, compartmentalizing sclerosis
What is the immunophenotype of PMBL?
Can be confirmed by histo chemistry or flow cytometry.
Express B-cell-associated Ag: CD19, CD20, CD22, CD79a, CD45
CD5- CD10- CD15-
CD30 Weakly +
TRAF-1+, c-Rel+
Typically do NOT express immunoglobulins.
B Cell transcription factors: PAX5, OCT2, BOB1 strongly expressed
Germinal center markers usually expressed CD10+ BCL6+ CD23+
How can biopsies of PMBL be obtained by?
Cervical Mediastinoscopy
Anterior mediastinotomy
Thoracoscopy
What are the differential diagnosis for PMBL?
Benign mediastinal tumors Malignant mediastinal tumors - Systemic lymphoma with secondary mediastinal involvement - Hodgkin Lymphoma Infectious entity (eg. Histoplasmosis) Inflammatory entity
How do you differentiate DLBCL from PMBL?
PMBLs typically express:
- CD30 + (weak)
- TRAF-1
- nuclear c-Rel
How do you differentiate Hodgkin Lymphoma and PMBL?
Via immunophenotyping. - classical HL: >>> CD15+ (85% of cases); >>> high levels of CD30 (>95% of cases); >>> lack of pan-B and pan-T cell antigens - PMBL: >>> express pan-B cell Ag >>> weak expression of CD30 >>> rarely express CD15
What is common between HL and PMBL?
Both more common in young women
Both not uncommonly present with large mediastinal mass
On biopsy, PMBL may have cells that resemble RS-cells
Some gene expression profiling similarity
What is a gray zone lymphoma?
Gray-zone lymphoma = B cell lymphoma, unclassifiable
- with features intermediate btwn DLBCL and cHL
What can you comment about the choice of therapy for PMBL?
Optimal treatment of PMBL is unknown with variation in clinical practice.
When possible, clinical trial is an option.
Outside of a clinical trial, tx options depend on patient, tumor characteristics ad physician comfort.
All patients are treated with induction Chemoimmunotherapy.
Use of RT as part of primary treatment is more controversial and depends on the choice of induction Chemoimmunotherapy and whether disease is present outside of the chest.
Choice of treatment also depend if PMBL is limited stage or advanced stage disease.
- limited stage meaning disease can be contained within one irradiation field
- advanced refers to disease that cannot be contained within one RT field; bulky; associated pericardial/pleural effusions
