Shao, Haipeng

BackgroundMycosis fungoides (MF) and Sézary Syndrome (SS) are clinically distinct cutaneous T‐cell lymphomas with strikingly similar morphologic and phenotypic features. Prior studies have suggested phenotypic differences based on markers of antigen experience, suggesting a different cell of origin.MethodsSeventy‐nine involved peripheral blood or bone marrow samples from 33 patients with SS and 19 patients with MF were studied by 10‐color flow cytometry, including CD62L, CD45RA, CCR4, and PD‐1. Gated tumor events were classified as naïve (TN), central memory (TCM), effector memory (TEM), or effector memory with reacquired CD45RA (TEMRA); based on CD62L+/CD45RA+, CD62L+/CD45RA−, CD62L−/CD45RA−, or CD62L−/CD45RA+ phenotype, respectively. Sequential specimens were compared to assess for phenotypic stability.ResultsThe naïve/memory phenotype of the neoplastic T‐cells was markedly heterogeneous, with a dominant TN, TCM, TEM, or TEMRA subset on 11 (14%), 32 (41%), 30 (38%), and 6 (8%) cases, respectively. There was no correlation between the diagnosis of MF or SS and putative cell of origin (P = 0.4). Overexpression of CCR4 and PD1 was observed in most cases, with higher intensity in SS compared to MF. The naïve/memory phenotype remained the same for 10 patients up to 273 days after the initial analysis; while on six patients, the naïve/memory phenotype was different from the original phenotype.ConclusionsBoth SS and MF can have phenotypic features of any of the major naïve/memory T‐cell subsets, which questions the current principle of “cell‐of‐origin” distinction between SS and MF. Phenotypic shifts within these subsets are common, suggesting a functional state rather than a cell‐of‐origin surrogate. © 2018 International Clinical Cytometry Society

Nonhepatosplenic/noncutaneous γδ peripheral T-cell lymphoma (NHNCγδ PTCL) represents a miscellaneous group of unrelated T-cell lymphomas of which only isolated cases have been reported. We describe two cases of transformation from T-lymphoblastic leukemia/lymphoma to NHNCγδ PTCL. Transformation into more aggressive disease is a rare event in T-cell lineage-derived hematologic malignancies compared to B-cell neoplasms. Nevertheless, both of our cases involved relapse as PTCL manifested with skin involvement and an overt shift from blastic morphology to large granular leukemia-like mature T cells. Among other notable molecular characteristics, expression of immature markers such as TdT was lost in both cases. Based on cytogenetics, phenotype, and morphology, both patients represent a novel phenomenon of clonal transformation from T-ALL to PTCL which has rarely been reported in the literature. Such transformation may carry important diagnostic and biological implications.

Indeterminate dendritic cell neoplasm (IDCN) is an exceedingly rare and mostly cutaneous histiocytosis, frequently associated with other hematopoietic malignancies. We report 2 cases of multilesional cutaneous IDCN. A 55‐year‐old male with no associated malignancy and complete response to ultraviolet phototherapy; and a 72‐year‐old male with chronic myelomonocytic leukemia (CMML). Both cases showed histiocytoid cytology, positivity for CD1a and no expression of langerin or BRAFV600E. With our patients, the literature describes 79 cases of IDCNs, including 65 (82%) with only skin involvement, 7 cases (9%) with involvement of skin and a second site, 5 cases (6%) involving lymph nodes only, 1 splenic lesion and 1 systemic disease. Seventeen cases (22%) were associated with other hematopoietic malignancies, most commonly CMML (6 cases), follicular lymphoma (4 cases) and acute myeloid leukemia (3 cases). All IDCNs associated with myeloid malignancies were limited to the skin, while most cases associated with lymphoma were limited to lymph nodes. Reported responses of cutaneous lesions to ultraviolet phototherapy are encouraging, while systemic chemotherapy is appropriate for clinically aggressive cases and treatment of associated malignancies. Recognition of the clinico‐morphologic spectrum of IDCNs should prevent misdiagnoses and prompt investigation of possible associated neoplasms.