Fatal Case of Primary Cutaneous Aggressive T-Cell Lymphoma Switching From a CD4+ to a CD8+ Phenotype: Progressive Disease With Bexarotene and Romidepsin Treatment

Spatially Guided and Single Cell Tools to Map the Microenvironment in Cutaneous T-Cell Lymphoma

Mycosis fungoides (MF) and Sézary syndrome (SS) are two closely related clinical variants of cutaneous T-cell lymphomas (CTCL). Previously demonstrated large patient-to-patient and intra-patient disease heterogeneity underpins the importance of personalized medicine in CTCL. Advanced stages of CTCL are characterized by dismal prognosis, and the early identification of patients who will progress remains a clinical unmet need. While the exact molecular events underlying disease progression are poorly resolved, the tumor microenvironment (TME) has emerged as an important driver. In particular, the Th1-to-Th2 shift in the immune response is now commonly identified across advanced-stage CTCL patients. Herein, we summarize the role of the TME in CTCL evolution and the latest studies in deciphering inter- and intra-patient heterogeneity. We introduce spatially resolved omics as a promising technology to advance immune-oncology efforts in CTCL. We propose the combined implementation of spatially guided and single-cell omics technologies in paired skin and blood samples. Such an approach will mediate in-depth profiling of phenotypic and molecular changes in reactive immune subpopulations and malignant T cells preceding the Th1-to-Th2 shift and reveal mechanisms underlying disease progression from skin-limited to systemic disease that collectively will lead to the discovery of novel biomarkers to improve patient prognostication and the design of personalized treatment strategies.

Immunophenotypic switch in cutaneous T-cell lymphoma: A series of three cases and review of the literature

Primary cutaneous T-cell lymphoma (CTCL) comprises a heterogeneous group of neoplasms with variable clinical behavior. Immunophenotypic switch (IS) is a phenomenon that occurs during lymphoma progression and is defined by an alteration in the immunophenotypic expression of a tumor with retention of its genotypic signature. This has been well-recognized in hematopoietic neoplasms; however, it has been rarely reported in CTCL and its clinical implications are not well understood. We present the clinical, histopathologic, immunophenotypic, and genetic findings of three cases of CTCL that demonstrated IS post treatment with variable outcomes. We add our cases to the small number previously reported to increase awareness of this phenomenon and its diagnostic challenge.

Atypical Presentation of Primary Cutaneous CD8 Positive Aggressive Epidermotropic Cytotoxic T-Cell Lymphoma

Primary cutaneous CD8 positive aggressive epidermotropic cytotoxic T-cell lymphoma (PCAT) is a rare and heterogeneous entity with less than 100 published cases to date. A 68-year-old man was following up for an inflammatory lichen–lupus overlap dermatosis of 3 years duration. Treatment with methotrexate was started, observing a dramatic change in the skin lesions that became infiltrated plaques and generalized ulcerated tumours distributed over trunk and extremities. Histological study showed marked epidermotropism of CD8 positive cells and monoclonality was demonstrated by the polymerase chain reaction. Diagnosis of PCAT was concluded. Treatment with polychemotherapy was indicated. The PCAT is characterized by a rapid clinical history of generalized papules, plaques, nodules and tumours with frequent ulceration and necrosis. Although it has no pathognomonic clinical features, there are clinical, histological and prognostic data that define them as a group and differentiate them from other lymphomas. Exceptionally, there are cases reported which have been triggered following treatment with immunosuppressive drugs. In our patient we think that PCAT was triggered by the transformation of a pre-existing dermatosis, which had never showed a lymphoproliferative profile in biopsies before. A possible pathogenic mechanism is that in some inflammatory dermatoses, chronic antigenic stimulation in a situation of iatrogenic immunosuppression may favour the development of a malignant clonal T cell.