What are the morphological patterns of anaplastic large cell lymphoma (ALCL)?

Updated: May 08, 2020
  • Author: Delong Liu, MD, PhD; Chief Editor: Emmanuel C Besa, MD  more...
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Histologically, ALCL is characterized by sheets of large pleomorphic cells with abundant cytoplasm, horseshoe- or wreath-shaped nuclei, and multiple prominent nucleoli. These hallmark tumor cells may be multinucleated and can be similar to Reed-Sternberg cells in appearance

In ALK-positive systemic ALCL, the following 5 morphological patterns can be recognized [15] :

  • Common pattern (60%) - Neoplastic lymphocytes exclusively consist of large cells, frequently with hallmark appearance and at times resembling Reed-Sternberg cells

  • Lymphohistiocytic pattern (10%) - Characterized by tumor cells admixed with a large number of reactive histiocytes; the latter may mask the malignant cells, which are often smaller than in the common pattern and cluster around blood vessels

  • Small cell pattern (5–10%) - Shows a predominant population of small to medium-sized neoplastic cells with irregular nuclei; hallmark cells are always present and are often concentrated around blood vessels

  • Hodgkinlike pattern (3%) - Characterized by morphological features mimicking nodular sclerosing Hodgkin lymphoma

  • Composite pattern (15%) - More than one pattern may be seen in a single lymph node biopsy

In ALK-negative systemic ALCL, the small cell pattern is not recognized. Otherwise, it has similar morphological patterns.

In the WHO-European Organization for Research and Treatment of Cancer (EORTC) classification, PC-ALCL is described as having anaplastic, pleomorphic, and immunoblastic morphology. However, an inflammatory pattern has also been recognized and divided into a neutrophil-rich or a lymphohistiocytic pattern depending on the type of inflammatory cells. [16, 17]

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