Microvillous lymphoma is a rare B-cell lymphoma composed of large transformed lymphocytes. They can be recognized using specific criteria.


Diagnostic criteria:

(1) large transformed lymphocytes

(2) growth pattern either diffuse or sinusoidal

(3) cytoplasmic projections best seen on electron microscopy

(4) B cell immunophenotype (CD20 positive)

(5) negative for both CD30 and epithelial membrane antigen (EMA)


Additional findings:

(1) frequently positive for CD56 (the neural cell adhesion molecule, NCAM)

(2) clonal rearrangement of the immunoglobulin heavy chain gene

(3) often express CD74, CDw75 and bcl-2 protein


Differential diagnosis:

(1) anaplastic large cell lymphoma: CD30 positive and usually EMA positive


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