Does a subset of mature T-cell leukemias with features akin to T-cell prolymphocytic leukemia but lacking rearrangement of the TCL1 represent peripheral T-cell lymphoma, NOS in a leukemic phase?

In the current WHO classification, a T-cell prolymphocytic leukemia (T-PLL) diagnosis requires lymphocytosis of >5 × 109/L, evidence of monoclonality, and TCL1A or MTCP1 rearrangement. However, the 2019 consensus document suggested that in the absence of rearrangement of TCL1 -family, the presence of abnormalities involving chromosome 11 (11q22.3; ATM), chromosome 8 (idic(8)(p11), t(8;8), trisomy 8q), 5, 12, 13, 22, or a complex karyotype, as well as involvement specific sites (e.g., splenomegaly, effusions) would suffice for a diagnosis of T-PLL. We present a patient diagnosed with T-PLL with MTCP1 rearrangement who was successfully treated with alemtuzumab followed by consolidative allogeneic unrelated donor stem cell transplantation. Eight years later, the patient presented with inguinal lymphadenopathy with features more akin to peripheral T-cell lymphoma, NOS (PTCL, NOS) of the GATA3 subtype, and there was no evidence of peripheral blood involvement. However, the lymphoma cells were clonally related to those at presentation. Currently, literature on T-PLL-like cases lacking the rearrangement of TCL1A is limited, and the possibility of whether a proportion of such cases could represent PTCL, NOS (with leukemic involvement) needs consideration.