Abstract
Anaplastic large cell lymphoma (ALCL) represents a group of malignant T-cell lymphoproliferations that share morphological and immunophenotypical features, namely strong CD30 expression and variable loss of T-cell markers, but differ in clinical presentation and prognosis. The recognition of anaplastic lymphoma kinase (ALK) fusion proteins as a result of chromosomal translocations or inversions was the starting point for the distinction of different subgroups of ALCL. According to their distinct clinical settings and molecular findings, the 2016 revised World Health Organization (WHO) classification recognizes four different entities: systemic ALK-positive ALCL (ALK+ ALCL), systemic ALK-negative ALCL (ALK− ALCL), primary cutaneous ALCL (pC-ALCL), and breast implant-associated ALCL (BI-ALCL), the latter included as a provisional entity. ALK is rearranged in approximately 80% of systemic ALCL cases with one of its partner genes, most commonly NPM1, and is associated with favorable prognosis, whereas systemic ALK− ALCL shows heterogeneous clinical, phenotypical, and genetic features, underlining the different oncogenesis between these two entities. Recognition of the pathological spectrum of ALCL is crucial to understand its pathogenesis and its boundaries with other entities. In this review, we will focus on the morphological, immunophenotypical, and molecular features of systemic ALK+ and ALK− ALCL. In addition, BI-ALCL will be discussed.
Highlights
Anaplastic large cell lymphoma (ALCL) represents a group of malignant lymphoproliferations sharing morphological and immunophenotypic features, but exhibiting different clinical and genetic characteristics [1]
ALCL was recognized for the first time by Stein et al in 1985 as “anaplastic large cell Ki-1-positive lymphomas”; an aggressive non-Hodgkin’s lymphoma (NHL) exhibiting a morphology suggestive of “malignant histiocytosis” (MH), but with immunohistochemical features overlapping with those of classic Hodgkin’s lymphoma (CHL)
ALCL encompasses a spectrum of mature T-cell malignancies sharing certain features such as anaplastic cytology, strong CD30 expression, and variable loss of T-cell markers, but displaying different clinical presentations, molecular features, and oncogenic mechanisms
Summary
Anaplastic large cell lymphoma (ALCL) represents a group of malignant lymphoproliferations sharing morphological and immunophenotypic features, but exhibiting different clinical and genetic characteristics [1]. ALCL was recognized for the first time by Stein et al in 1985 as “anaplastic large cell Ki-1-positive lymphomas”; an aggressive non-Hodgkin’s lymphoma (NHL) exhibiting a morphology suggestive of “malignant histiocytosis” (MH), but with immunohistochemical features overlapping with those of classic Hodgkin’s lymphoma (CHL). This entity was defined by a proliferation of large lymphoid cells with a cohesive growth pattern with a tendency to invade lymph node sinuses and strong. The new insights about BI-ALCL will be discussed (Table 1)
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