Primary mediastinal (thymic) large B-cell lymphoma

Name
Primary mediastinal (thymic) large B-cell lymphoma
ICD-O-3 Morphology
9679/3
Effective 2001 and later
Reportable
for cases diagnosed 2001 and later
Primary Site(s)
C379, C383
Do not assign this histology just because the mediastinum is involved. Only assign this histology when the diagnosis is stated as “primary mediastinal."

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Grade
6 - B-cell
Module Rule
None
Alternate Names
Med-DLBCL
Mediastinal large B-cell lymphoma
PMBL
Thymic large B-cell lymphoma
Definition
Subtype of diffuse large B-cell lymphoma, large transformed cells resembling centroblasts or immunoblasts, relatively abundant pale cytoplasm often with distinct cytoplasmic membrane; apparently derived from thymus medullary B cells, may occur as secondary malignancy following nodular sclerosing Hodgkin lymphoma.
Abstractor Notes
Code the primary site to C379 (thymus) or C383 (mediastinum) based on the physician's statement. For either thymus or mediastinal primaries, the mediastinal and cervical lymph nodes may be involved.

PMBL most likely arises within the thymus. Patients present with a localized anterosuperior mediastinal mass. The mass is often bulky and frequently invades adjacent structures such as lungs, pleura, or pericardium. Spread to supraclavicular and cervical LN can occur.

Workup should be done to exclude a secondary mediastinal involvement by a DLBCL versus a primary mediastinal B-cell lymphoma through the absence of bone marrow involvement and lymph node involvement outside of the region.
Definitive Diagnostic Methods
Genetic testing
Histologic confirmation
Immunophenotyping
Genetics Data
Comparative genomic hybridzation (CH) demonstrated gains in chromosome 9p24 and 2p15
Genomic hybridization in chromosome X-p11.4-21
Immunoglobulin genes clonally rearranged
Immunophenotyping
CD19+
CD20+
CD22+
CD30 weakly positive and heterogeneous
CD79a+
Lacks immunoglobulin (Ig)
Treatments
Chemotherapy
Radiation
Transformations to
There are no known transformations
Transformations from
There are no known transformations
Corresponding ICD-9 Codes
200.7 Large cell lymphoma
Corresponding ICD-10 Codes
C83.3 Diffuse non-Hodgkins lymphoma, large cell (diffuse)
Corresponding ICD-10-CM Codes (effective October 1, 2015 U.S. only)
C85.2 Mediastinal (thymic) large B-cell lymphoma
Signs and Symptoms
Drenching night sweats
Fatigue
Fever (for no known reason)
Localized anterosuperior mediastinal mass
Pain in the chest, abdomen, or bones (for no known reason)
Painless swelling in the lymph nodes
Skin rash or itchy skin
Superior vena cava syndrome (due to mediastinal mass)
Weight loss (for no known reason)
Diagnostic Exams
Bone marrow aspiration and biopsy
CT (CAT) scan
Complete blood count (CBC)
Laparoscopy (rarely performed)
Laparotomy (rarely performed)
MRI (magnetic resonance imaging)
PET (positron emission tomography) scan
Progression and Transformation
None
Epidemiology and Mortality
Age: 35 years median age (occurs predominantly in young adults)
Incidence: 2-4% of non-Hodgkin lymphomas
Sex: female predominance
Survival: beyond 2 years