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Myeloid neoplasms and acute leukemias include different entities that have been recently re-classified taking into account molecular and clinicopathological features. The myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) category comprises a heterogeneous group of hybrid neoplastic myeloid diseases characterized by the co-occurrence of clinical and pathological features of both myelodysplastic and myeloproliferative neoplasms. The most frequent entity in this category is chronic myelomonocytic leukemia (CMML) which is, after acute myeloid leukemia (AML), the main myeloid disorder prone to develop cutaneous manifestations. Skin lesions associated with myelodysplastic and myeloproliferative neoplasms include a broad clinical, histopathological and molecular spectrum of lesions, poorly understood and without a clear-cut classification in the current medical literature. The aim of this review is to describe and classify the main clinical, histopathological and molecular patterns of cutaneous lesions in the setting of MDS/MPN in order to improve the diagnostic skills of the dermatologists, hematologists and pathologists who deal with these patients.

Anaplastic large cell lymphoma (ALCL) is a mature T-cell lymphoma that can present as a systemic or primary cutaneous disease. Systemic ALCL represents 2% to 5% of adult lymphoma but up to 30% of all pediatric cases. Two subtypes of systemic ALCL are currently recognized on the basis of the presence of a translocation involving the anaplastic lymphoma kinase ALK gene. Despite considerable progress, several questions remain open regarding the pathogenesis of both ALCL subtypes. To investigate the molecular pathogenesis and to assess the relationship between the ALK(+) and ALK(-) ALCL subtypes, we performed a genome-wide DNA profiling using high-density, single nucleotide polymorphism arrays on a series of 64 cases and 7 cell lines. The commonest lesions were losses at 17p13 and at 6q21, encompassing the TP53 and PRDM1 genes, respectively. The latter gene, coding for BLIMP1, was inactivated by multiple mechanisms, more frequently, but not exclusively, in ALK(-)ALCL. In vitro and in vivo experiments showed that that PRDM1 is a tumor suppressor gene in ALCL models, likely acting as an antiapoptotic agent. Losses of TP53 and/or PRDM1 were present in 52% of ALK(-)ALCL, and in 29% of all ALCL cases with a clinical implication.

Primary cutaneous γδ T-cell lymphomas (PCGD-TCLs) are considered a subgroup of aggressive cytotoxic T-cell lymphomas (CTCLs). We have taken advantage of a new, commercially available antibody that recognizes the T-cell receptor-γ (TCR-γ) subunit of the TCR in paraffin-embedded tissue. We have analyzed a series of 146 primary cutaneous T-cell lymphomas received for consultation or a second opinion in the CNIO Pathology Department. Cases were classified according to the World Health Organization 2008 classification as mycosis fungoides (MF; n=96), PCGD-TCLs (n=5), pagetoid reticulosis (n=6), CD30(+) primary cutaneous anaplastic large cell lymphomas (n=5), primary cutaneous CD8 aggressive epidermotropic CTCLs (n=3), primary cutaneous CTCL, not otherwise specified (n=4), and extranodal nasal-type NK/T-cell lymphomas primarily affecting the skin or subcutaneous tissue (n=11). Sixteen cases of the newly named lymphomatoid papulosis type D (LyP-D; n=16) were also included. In those cases positive for TCR-γ, a further panel of 13 antibodies was used for analysis, including TIA-1, granzyme B, and perforin. Clinical and follow-up data were recorded in all cases. Twelve cases (8.2%) were positive for TCR-γ, including 5 PCGD-TCLs, 2 MFs, and 5 LyP-Ds. All 5 PCGD-TCL patients and 1 MF patient died of the disease, whereas the other MF patient and all those with LyP-D were alive. All cases expressed cytotoxic markers, were frequently CD3(+)/CD8(+), and tended to lose CD5 and CD7 expressions. Eight of 12 and 5 of 11 cases were CD30(+) and CD56(+), respectively. Interestingly, 5/12 TCR-γ-positive cases also expressed TCR-BF1. All cases analyzed were negative for Epstein-Barr virus-encoded RNA. In conclusion, TCR-γ expression seems to be rare and is confined to cytotoxic primary cutaneous TCLs. Nevertheless, its expression is not exclusive to PCGD-TCLs, as TCR-γ protein can be found in other CTCLs. Moreover, its expression does not seem to be associated with bad prognosis by itself, as it can be found in cases with good and bad outcomes.

We have reviewed clinically, morphologically, and immunophenotypically a series of 14 Epstein-Bar virus (EBV)+ cutaneous natural killer cell (NK)/T-cell lymphoma from Peru. Most (11 out of 14) of these cases fit well into the category of Hydroa vacciniforme-like lymphoma (HVLL), but 3 have a different clinical presentation, without facial involvement. In all 14 cases, skin lesions present in both the sun-exposed and nonexposed areas exhibited a slowly progressive relapsing course, changing from edema, to blistering, ulceration, and final scarring. The immunophenotype had a cytotoxic T or NK-cell lineage. The mean time of disease before admission to hospital was 69 months (range, 6 mo to 31 y). Only 2 patients had fever, hepatosplenomegaly, systemic lymphadenopathy, and a high lactate dehydrodenage (LDH) level at the time of diagnosis, whereas 10 had facial swelling. After treatment, only 4 patients remain alive, although with persistent disease. Ten patients died after a mean follow-up of 11.6 months after the initial diagnosis (range, 1 to 32 mo), because of concurrent infections (4 cases), disease progression (4 patients) or both (2 patients). Endemic Epstein-Bar virus (EBV)-positive cutaneous NK/T-cell lymphoproliferative disorders in childhood and early adulthood are characterized by a protracted clinical course, eventually leading to an aggressive phase characterized by concurrent infections and disease progression.

Cutaneous CD4 small/medium-sized pleomorphic T-cell lymphoma (CSTCL) is a cutaneous T-cell lymphoma defined by a predominance of small-to-medium-sized CD4 pleomorphic T cells, with a favorable clinical course. Cases are also characterized by the presence of a rich infiltrate of reactive B cells. Recently, it has been reported that follicular helper T cells (TFH cells) display a distinct gene expression profile, positive for PD-1, CXCL13, and BCL-6. We report for the first time the expression of PD-1 and other TFH cell markers in CSTCLs and discuss its biologic significance. Sixteen CSTCLs were included in this study, and also 20 reactive inflammatory conditions, 10 primary cutaneous marginal zone, 10 follicular center lymphomas, and 5 primary CD30 cutaneous lymphomas. They were immunohistochemically analyzed for a large panel of markers. Double immunoperoxidase labeling of paraffin sections was performed for PD-1, OCT-2, and BCL-6. Clonal Ig and T-cell receptor rearrangements and Epstein-Barr virus-encoded RNA expression were also evaluated. Morphologic and clinical data were reviewed. Histologic examination showed a dense polymorphic lymphoid infiltrate throughout the dermis. Atypical large CD4 cells were positive for PD-1, CXCL13, and BCL-6 in all cases, and were attached in small clusters, or formed rosettes around CD30/OCT-2+ B blast cells. Epstein-Barr virus was not apparent in any of the cases. A dominant T-cell clone was identified in 14 cases, whereas polymerase chain reaction IgH gene rearrangement studies showed that all cases were polyclonal. None of the patients had lymphadenopathy or showed any evidence of systemic disease, nor did they have any previous history of mycosis fungoides or drug reactions. FTH cell markers are not exclusive to angioimmunoblastic lymphadenopathy but may also be seen in neoplastic cells of CSTCLs. Moreover, these findings suggest that B-cell stimulation by FTH could also take place in some cutaneous T-cell lymphomas.