ABSTRACT
Anaplastic large cell lymphoma (ALCL) is a T-cell lymphoma composed of large pleomorphic cells, which have irregular kidney-shaped nuclei and are positive for CD30, and in majority of cases anaplastic lymphoma kinase (ALK) protein. ALCL involves the lymph nodes and extranodal sites, including the skin, soft tissues, lung, and bone, and less often gastrointestinal tract. ALK± ALCL is a T-cell lymphoma usually composed of large cells with abundant cytoplasm and pleomorphic, often horseshoe-shaped nuclei, with a translocation involving the ALK gene and the expression of ALK protein. Giant-cell variant of ALCL shows large cells with irregular often bizarre nuclei. ALCL often involves extranodal sites, including the cerebrospinal fluid, liver, skin, spleen, lungs, and bone/bone marrow, body cavities, and soft tissues. The ALK expression in ALCL may be nuclear, nucleolar, and cytoplasmic. Correlation with clinical data is necessary to differentiate lymphatic drainage from cutaneous ALCL or lymphomatoid papulosis and systemic ALCL.
