Secondary Lymphoid Tissues ›› Lymph Node ›› Neoplastic: Non-Hodgkin Lymphoma

T-cell Lymphoma: ALK+ Anaplastic Large Cell Lymphoma*


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› Microscopic Features:

• Sheets or clusters of Large (>2.5x the size of a mature lymphocyte or equal or > than the size of a histiocyte) abnormal lymphocytes usually involving lymph node but may involve other tissue
• Anaplastic Large Cell Lymphoma (ALCL) ususally have horse-shoe shaped large abnormal cells known as "hallmark cells"
• ALCL typically involves the lymph node sinuses but it may have a diffuse pattern of growth as well

› Normal % blood-PB, marrow-BM, lymphoid tissue-LN:

• PB: N/A
• BM: N/A
• LN: N/A

› May Resemble:

• Non-neoplastic reactive Lymph node [Compare]
• Diffuse Large B-cell Lymphoma [Compare]
• Burkitt Lymphoma [Compare]
• Small Lymphocytic Lymphoma [Compare]
• Mantle Cell Lymphoma [Compare]
• Follicular Lymphoma [Compare]
• Carcinoma
• Melanoma

› Differential Diagnoses:

Diffuse Large B-cell Lymphoma Mantle cell lymphoma (blastoid variant) Follicular lymphoma (high grade, e.g. 3B) Burkitt Lymphoma Small Lymphocytic Lymphoma (SLL: The CLL equivalent in tissue) Mantle Cell Lymphoma Non-neoplastic reactive Lymph node Hodgkin Lymphoma

› Classic Immunophenotype:

• CD3+
• CD30+
• ALK+
• CD19-
• CD20-

› Misc:

• Most are associated with the t(2;5) ALK1-NPM translocation