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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.
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
Comparative genomic hybridzation (CH) demonstrated gains in chromosome 9p24 and 2p15