Commentary

Large-cell transformation of mycosis fungoides–differential diagnosis with implications for clinical management: A consensus statement of the US Cutaneous Lymphoma Consortium

Mycosis fungoides with large-cell transformation (MF-LCT) occurs in a minor proportion of aggressive lesions, which express CD30 similar to primary cutaneous anaplastic large-cell lymphoma (pcALCL). We investigated the differences in spatially resolved transcriptome profiles of MF-LCT and pcALCL using CD30 morphology markers and 28 and 24 regions of interest (ROIs) in MF-LCT and pcALCL, respectively. Differentially expressed genes, pathway analysis, and immune-cell deconvolution by selective analysis of CD30-positive tumor cells and CD30-negative extratumoral areas were undertaken. In CD30-positive ROIs of MF-LCT, 190 differentially expressed genes were upregulated (29 were directly or indirectly associated with extracellular matrix remodeling), whereas 255 differentially expressed genes were downregulated, compared with those of pcALCL. Except for cornified envelope formation and keratinization, all six pathways enriched in CD30-positive ROIs of MF-LCT were associated with extracellular matrix remodeling. In CD30-positive ROIs in MF-LCT compared with those in pcALCL, immune-cell deconvolution revealed significantly increased fibroblasts and M2 macrophages (P = 0.012 and P = 0.023, respectively) but decreased M1 macrophages (P = 0.031). In CD30-negative ROIs in MF-LCT compared with those in pcALCL, memory B (P = 0.021), plasma (P = 0.023), and CD8 memory T (P = 0.001) cells significantly decreased, whereas regulatory T cells (P = 0.024) increased. Predomination of extracellular matrix remodeling pathways and immunosuppressive microenvironment in MF-LCT indicates pathophysiological differences between MF-LCT and pcALCL.

The emergence of a common progenitor cell has been postulated for the association of CD30-positive lymphoproliferative disease (LPD) and mycosis fungoides (MF) within the same patient. Up to now, no comprehensive analysis has yet addressed the genetic profiles of such concurrent lymphoma subtypes. We aimed to delineate the molecular alterations of clonally related CD30-positive LPD and MF occurring in the same two patients. We analyzed the molecular profile of 16 samples of two patients suffering both from CD30-positive LPD and MF being obtained over a time course of at least 5 years. To detect oncogenic mutations, we applied targeted sequencing technologies with a hybrid capture-based DNA library preparation approach, and for the identification of fusion transcripts, an anchored multiplex PCR enrichment kit was used. In all samples of CD30-positive LPD and MF, oncogenic fusions afflicting the Jak/signal transducer and activator of transcription signaling pathway were present, namely NPM1‒TYK2 in patient 1 and ILF3‒JAK2 in patient 2. Additional signal transducer and activator of transcription 5A gene STAT5A mutations exclusively occurred in lesions of CD30-positive LPD in one patient. CD30-positive LPD and MF may share genetic events when occurring within the same patients. Constitutive activation of the Jak/signal transducer and activator of transcription signaling pathway may play a central role in the molecular pathogenesis of both entities.

Cutaneous T-cell lymphomas are a heterogeneous group of lymphoproliferative disorders, characterized by infiltration of the skin by mature malignant T cells. Mycosis fungoides is the most common form of cutaneous T-cell lymphoma, accounting for more than 60% of cases. Mycosis fungoides in the early-stage is generally an indolent disease, progressing slowly from some patches or plaques to more widespread skin involvement. However, 20% to 25% of patients progress to advanced stages, with the development of skin tumors, extracutaneous spread and poor prognosis. Treatment modalities can be divided into two groups: skin-directed therapies and systemic therapies. Therapies targeting the skin include topical agents, phototherapy and radiotherapy. Systemic therapies include biological response modifiers, immunotherapies and chemotherapeutic agents. For early-stage mycosis fungoides, skin-directed therapies are preferred, to control the disease, improve symptoms and quality of life. When refractory or in advanced-stage disease, systemic treatment is necessary. In this article, the authors present a compilation of current treatment options for mycosis fungoides and Sézary syndrome.

SATB1 is an important T-cell specific chromatin organizer in cutaneous T-cell lymphoma, whereas its expression and function in mycosis fungoides (MF) remain ambiguous. Our study aimed to investigate the clinicopathological significance of SATB1 in a cohort of 170 patients with MF. SATB1 expression was heterogeneous among the patients with MF in each clinical stage. High SATB1 expression was associated with epidermal hyperplasia, eosinophil infiltration, less large-cell transformation, and favorable prognosis in MF cases. SATB1 and CD30 coexpression distinguished cutaneous CD30⁺ lymphoproliferative disorders from MF large-cell transformation. SATB1 silencing in MF lines showed that SATB1 upregulated the genes involved in eosinophil recruitment, including signal transducer and activator of transcription 3 and IL13, and downregulated the genes in cell-cycle progression, which may explain the inferior prognosis for low SATB1-expressing cases. Moreover, SATB1 was inversely correlated with PD-1 expression, indicating an exhausted status of SATB1-negative malignant T cells. SATB1 was positively correlated with toll-like receptors expression, suggesting innate immune activation in high SATB1-expressing MF cases. Therefore, variable SATB1 expression promotes heterogeneity in pathology and clinical outcome of patients with MF.

We examined patient characteristics, treatments, and outcomes of patients with transformed mycosis fungoides (tMF) from COMPLETE: a large, multicenter, prospective cohort study of peripheral T-cell lymphoma patients in the United States.

Patients with tMF were enrolled in COMPLETE at the time of transformation. For this analysis, we identified patients with tMF with completed baseline, treatment, and follow-up records. Median survival was assessed using Kaplan-Meier methodology.

Of the 499 patients enrolled in COMPLETE, 17 had tMF. Median age was 61; 53% were male, 9 had elevated lactate dehydrogenase, and 9 had lymph node involvement. Approximately one-quarter of the patients were African American and 47% had CD30+ disease. Median time to transformation was 53 months. All patients received systemic therapy, with 19% receiving concomitant radiotherapy. Most patients (87%) received single agents, including liposomal doxorubicin, pralatrexate, and gemcitabine. Eight patients (50%) had reported responses to therapy. Median survival was 18 months. One- and 2-year survival rates were 56% and 44%, respectively.

tMF often expresses CD30 and presents with lymph node involvement. Responses have been seen with single agents, but survival remains poor. Novel treatment approaches are urgently needed to improve outcomes.