Primary mediastinal (thymic) large B-cell lymphoma

ICD-O-3 Morphology

9679/3: Mediastinal large B-cell lymphoma
Effective 2001 and later


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."

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.

Diagnostic Confirmation

This histology can be determined by positive histology (including peripheral blood) with or without genetics and/or immunophenotyping. Review the Definitive Diagnostic Methods, Immunophenotyping and Genetics Data sections below, and the instructions in the Hematopoietic Manual for further guidance on assigning Diagnostic confirmation.


Not Applicable

Module Rule


Alternate Names

Mediastinal large B-cell lymphoma
Mediastinal diffuse large cell lymphoma with sclerosis
Primary mediastinal clear cell lymphoma of B-cell type [OBS]
Thymic large B-cell lymphoma


Primary mediastinal (thymic) large B-cell lymphoma (PMBL) is a mature aggressive large B-cell lymphoma (LBCL) of putative thymic B-cell origin arising in the mediastinum, with distinctive clinical, immunophenotypic, genotypic, and molecular features. Cases that arise outside the mediastinum are probably very uncommon, and cannot be confidently recognized without gene expression profiling studies.

Definitive Diagnostic Methods

Genetic testing
Histologic confirmation

Genetics Data

CIITA at 16p13.13
Immunoglobulin genes clonally rearranged
PDCD1LG1 (also called CF274 or PDL1)
PDCD1LG2 (also called PDL2)


BOB1 expression
CD19 expression
CD20 expression
CD22 expression
CD30 weakly positive and heterogeneous
CD79a expression
Ig functional gene arrangement
Immunoglobulin lacking
OCT2 expression
PAX5 expression
PU1 expression


Radiation therapy

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

C83.8 Other types of diffuse non-Hodgkin lymphoma

Corresponding ICD-10-CM Codes (U.S. only)

C85.2 Mediastinal (thymic) large B-cell lymphoma (effective October 01, 2015)

Signs and Symptoms

Drenching night sweats
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

Blood chemistry studies
CT (CAT) scan
Cytogenetic analysis
Flow cytometry
Laparoscopy (rarely performed)
Laparotomy (rarely performed)
Lymph node biopsy
PET (positron emission tomography) scan

Progression and Transformation


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


Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition)
IARC: Lyon 2017
Section: Mature B-cell neoplasms
Pages: 314-316

International Classification of Diseases for Oncology, Third Edition, Second Revision. Geneva: World Health Organization, 2020.
Section: ICD-O-3.2 (2020) Morphological Codes

National Cancer Institute
Section: General Information About Adult Non-Hodgkin Lymphoma (NHL)