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PD-L1/PD-1 Check Point in Anaplastic Large Cell Lymphoma, ALK+: A Case Report with Immunohistochemical and Molecular Study

Antonella Bianchi, Silvia Vallese, Ombretta Annibali

Anaplastic large cell lymphoma, ALK+ (ALK+ ALCL) is a T-cell lymphoma consisting of large and pleomorphic lymphoid cells, often with horseshoe-shaped nuclei, with a chromosomal translocation involving the ALK gene and expression of ALK protein and CD30. ALK+ ALCL must be distinguished from primary cutaneous ALCL and from other subtype of T-cell or B-cell lymphoma with anaplastic features and/or CD30 expression. PD-L1/PD-1 check point physiologically plays a key role in induction and maintenance of immune tolerance to self-antigens and limits normal immune response against microorganisms. PD-L1 has been demonstrated in the whole spectrum of normal hematopoietic and non-hematopoietic cells, as well as in a large variety of epithelial cells. Moreover, it is also very commonly expressed by a large number of malignant cell types of epithelial and hematopoietic cell origin, and its activation is one of the major mechanisms exerted by neoplastic cells to evade elimination by the host immune system. Here we report a case of an ALK+ ALCL, with confirmed FISH rearrangement of ALK gene, PD-L1-positive and discuss the molecular mechanism involved in its immunohistochemical profile.