Bullet Learning: Anaplastic Large T-Cell Lymphoma

50yoM with controlled HIV presented with slowly enlarging inguinal lymphadenopathy over the last 9 months. Flow cytometry and lymph node biopsy revealed an aberrant population of lymphoid cells. Here's the H&E:

What Stains Would You Get?

• 0%CD3
• 0%CD4
• 0%CD5
• 0%CD20

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Here are the results of IHC:

Stain	Result
CD3	Negative
CD4	Positive
CD5	Positive
CD20	Negative
CD30	Positive
CD45	Positive
ALK1	Positive

What is the diagnosis?

Anaplastic Large Cell Lymphoma (ALCL) – ALK-positive!

A subtype of peripheral T-cell lymphoma, it classically presents as large cells with abundant cytoplasm, pleomorphic, horseshoe-shaped nuclei, and CD30 positivity.

The presence of Alk1 positivity is associated with translocation t(2;5) producing the ALK1::NMP1 fusion gene. It is frequently associated with HIV, mycosis fungiodes, and pulmonary pseudotumors. The main differentials include Hodgkins Lymphoma (also CD30+, CD3-, CD20-), and Alk-negative ALCL.

Known as a moderately aggressive tumor, it has an overall prognosis better than other peripheral T cell lymphomas, including Alk1 negative ALCL, with 5 year survival of 80%. The presence of MYC rearrangement, small cell morphology, or lymphohistiocytic variant indicate a poor prognosis.

References:

https://www.ncbi.nlm.nih.gov/books/NBK537150/.