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Anaplastic large cell lymphoma, small cell variant
Anaplastic large cell lymphoma, T cell and Null cell type
Large cell (Ki1+) lymphoma [OBS]
ALCL is a T-cell lymphoma consisting of lymphoid cells that are usually large with abundant cytoplasm and pleomorphic, often horseshoe-shaped nuclei. Most cases express cytotoxic granule-associated proteins. The majority are positive for the Anaplastic large cell lymphoma kinase (ALK) protein.
Grade is T-cell (5) unless pathologist specifically designates as a B-cell (see G2 rule)
Note: This neoplasm has a small cell variant. (See below.) Anaplastic large cell lymphoma, ALK-positive (ALCL, ALK+) frequently involves both lymph nodes and extranodal sites. The most commonly involved extranodal sites include skin, bone, soft tissue, lung, and liver. Involvement of the GI system and CNS is rare. Mediastinal disease is less frequent than in Classical Hodgkin lymphoma. The evidence of bone marrow involvement is approximately 10%. The small cell variant may have a leukemic presentation with peripheral blood involvement. The majority of patients present with stage III-IV disease with peripheral blood and/or abdominal lymphadenopathy often associated with infiltrates and involvement of bone marrow. Patients often have B-symptoms, especially high fever. The immunophenotyping is vital in differentiating this neoplasm from large B-cell lymphoma with immunoblastic/plasmablastic features expressing ALK protein, rhabdomyosarcoma, and inflammatory myofibroblastic tumors.
Definitive Diagnostic Methods
Bone marrow biopsy
T-cell receptor (TCR) genes are clonally rearranged
t (2;5) (p23;q35)
Positive: ALK, CD2, CD4, CD5, CD30
Positive/Negative: CD45, CD56, EMA, granzyme B, perforin, TIA-1