Primary mediastinal B-cell lymphoma

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Primary mediastinal B-cell lymphoma, abbreviated PMBL, is an uncommon form of large B-cell lymphoma.

It is also known as primary mediastinal large B-cell lymphoma.

General

Features:[1][2]

  • Rare.
  • Young adults, more common in females (M:F = 1:2)
  • Mediastinum

It is distinguished from DLBCL based on the patient demographics, radiological staging (showing mainly mediastinal disease) and immunoprofile (typically CD23+/CD30+). PMBCL has a better prognosis than DLBCL.

Microscopic

Features:

  • Atypical large lymphoid cells - may be morphologically indistinguishable from DLBCL
  • Classically associated with:
    • Fibrosis
    • Clear cells.

Note:

  • Neither fibrosis or clear cells are required for the diagnosis nor are they pathognomonic.[3]

DDx:

  • Other types of DLBCL (radiological assessment is important - PMBCL is centred in the mediastinum)
  • B-cell lymphoma with features intermediate between DLBCL and classical Hodgkins lymphoma
  • Poorly differentiated carcinoma.

IHC

  • Pan B-cell markers
  • CD10 in minority (~20%)
  • CD23 and CD30 expression more common (~70% and ~85% respectively)
  • EBV negative

Images

  • PMBL - very high mag. (WC)

  • PMBL - intermed. mag. (WC)

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MASS, ANTERIOR MEDIASTINAL, CORE BIOPSY:
- LARGE B-CELL LYMPHOMA IN A FIBROTIC BACKGROUND WITH NECROSIS, SEE COMMENT

COMMENT:
Morphology:
 Tumour cells: size ~2x a mature lymphocyte, a moderate quantity of grey/basophilic
  cytoplasm, no clear cells are identified.
 Cells intermixed with tumour: mature lymphocytes, rare eosinophils.
 Architecture: no gland formation, discohesive, no follicles apparent, extensive fibrosis.

Tumour cells:
POSITIVE: CD45, CD20, CD10, BCL-6, BCL-2.
NEGATIVE: pankeratin, PLAP, CD3, CD30.
Ki-67: 50% of large (lymphoid) cells.

See also

References

  1. ↑ Johnson, PW.; Davies, AJ. (2008). "Primary mediastinal B-cell lymphoma.". Hematology Am Soc Hematol Educ Program: 349-58. doi:10.1182/asheducation-2008.1.349. PMID 19074109.
  2. ↑ Coso, D.; Rey, J.; Bouabdallah, R. (Feb 2010). "[Primary mediastinal B-cell lymphoma]". Rev Pneumol Clin 66 (1): 32-5. doi:10.1016/j.pneumo.2009.12.007. PMID 20207294.
  3. ↑ van Besien, K.; Kelta, M.; Bahaguna, P. (Mar 2001). "Primary mediastinal B-cell lymphoma: a review of pathology and management.". J Clin Oncol 19 (6): 1855-64. PMID 11251018.
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