Tumour-like lesions with T-cell predominance

WHO 2022: Tumour-like lesions with T-cell predominance: a new class of tumour-like lesions.


The new family of tumour-like lesions with T-cell predominance in WHO-HAEM5 includes three distinct entities:

  • indolent T-lymphoblastic proliferation (ITLP)

  • Kikuchi-Fujimoto disease (KFD)

  • autoimmune lymphoproliferative syndrome (ALPS).


Indolent T-lymphoblastic proliferation (ITLP) may occur by itself or in association with benign and neoplastic follicular dendritic cell proliferations and other malignancies. It shows clusters or confluent sheets of lymphoid cells which can range in appearance from small lymphocytes to slightly larger cells with more open chromatin (morphologically consistent with thymocytes as seen in the normal thymus), which may be mistaken for T-lymphoblastic leukaemia/lymphoma due to TdT expression. However, ITLP may distort, but typically does not obliterate the architecture of the involved tissues, the TdT+ cells are not as atypical as those encountered in lymphoblastic leukaemia/lymphoma, and ITLP does not show monoclonal TCR gene rearrangement.


Kikuchi-Fujimoto disease (KFD) commonly shows large aggregates and sheets of T

immunoblasts and histiocytes, accompanied by prominent apoptosis in lymph nodes, mimicking peripheral T-cell lymphoma NOS. Clues to the correct diagnosis include the typical clinical scenario of cervical lymphadenopathy in a young woman, the

circumscribed and non-expansile nature of the nodal infiltrate, presence of a significant component of plasmacytoid dendritic cells (CD123+) and presence of many histiocytes that express myeloperoxidase.


Autoimmune lymphoproliferative syndrome (ALPS), which is associated with autoimmunity and germline or somatic pathogenetic changes in genes involved in FAS-mediated apoptosis, has nodal or extranodal infiltrates of CD4-, CD8-T cells, which may appear as atypical medium-sized cells with clear cytoplasm that may mimic lymphoma. The clinical setting (young patient age) and lack of destructive infiltrate may provide clues to its benign nature.