Immunophenotypic shift of CD4 and CD8 antigen expression in primary cutaneous T-cell lymphomas: a clinicopathologic study of three cases

Phenotypic switch in mycosis fungoides: A tertiary cancer center experience

BACKGROUND

Changes in immunophenotype in mycosis fungoides (MF) are rarely reported, making this phenomenon a diagnostic challenge with unclear significance for the disease's biological behavior. This study examines a large series of MF patients who exhibited a phenotype switch (PS) and analyzes their clinical and histopathologic characteristics.

DESIGN

Institutional files were searched for MF cases exhibiting PS between 2010 and 2020. Clinical, follow-up, and histopathological data were collected.

RESULTS

Forty-two biopsies from 32 patients (13 women and 19 men, median age 67.5) showed PS. Eight patients (25 %) experienced multiple PS during their disease course. The median time for PS was 22 months from the initial diagnosis. In 5 cases tested, identical TCR clone peaks were detected in the immunophenotypically distinct lesions. Median follow-up was 14.5 months. Among deceased patients, median time from MF diagnosis to PS was 20.6 months, while among the patients who were still alive, median time was 44.1 months.

CONCLUSION

MF biopsies can show PS during the course of the disease and may indicate a change in clinical behavior. 28.1 % of patients displayed more than one PS, further indicating high plasticity of MF cells. No obvious association was found between PS and therapy initiation or response. Features that appeared to portend a worse clinical course were earlier PS in the course of the disease and PS from CD4-/CD8-to CD8+, and CD8+ to CD4-/CD8-. Awareness of this phenomenon is crucial to avoid misdiagnosing phenotypically distinct lymphomas as second primaries and to alert clinicians about potential changes in the disease's clinical course.

Read the clonotype: Next-generation sequencing-based lymphocyte clonality analysis and perspectives for application in pathology

Clonality assessment using the unique rearrangements of immunoglobulin (IG) and T-cell receptor (TR) genes in lymphocytes is a widely applied supplementary test for the diagnosis of B-cell and T-cell lymphoma. To enable a more sensitive detection and a more precise comparison of clones compared with conventional clonality analysis based on fragment analysis, the EuroClonality NGS Working Group developed and validated a next-generation sequencing (NGS)-based clonality assay for detection of the IG heavy and kappa light chain and TR gene rearrangements for formalin-fixed and paraffin-embedded tissues. We outline the features and advantages of NGS-based clonality detection and discuss potential applications for NGS-based clonality testing in pathology, including site specific lymphoproliferations, immunodeficiency and autoimmune disease and primary and relapsed lymphomas. Also, we briefly discuss the role of T-cell repertoire of reactive lymphocytic infiltrations in solid tumors and B-lymphoma.

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.

Histopathologic Characterization of Mogamulizumab-associated Rash

Rash is one of the most common adverse events observed with mogamulizumab, an anti-C-C chemokine receptor 4 monoclonal antibody approved for previously treated mycosis fungoides (MF) and Sezary syndrome (SS). Given the nonspecific clinical presentations of this rash, histopathologic distinction from MF/SS is critical for informing clinical management. We performed a comprehensive characterization of the histopathologic findings in mogamulizumab-associated rash (MAR) with the integration of high-throughput sequencing of T-cell receptor (TCR) genes. Fifty-two biopsy specimens from 19 patients were evaluated retrospectively. Three major histologic reaction patterns were identified: spongiotic/psoriasiform dermatitis (33/52), interface dermatitis (11/52), and granulomatous dermatitis (8/52). Almost half of the specimens (21/52) showed at least 2 of these reaction patterns concurrently. Dermal eosinophils were not a consistent feature, being present in only half (27/52) of specimens and prominent in only 3. Features mimicking MF/SS, including lymphocyte exocytosis, lamellar fibroplasia, and adnexal involvement, were commonly seen but tended to be focal and mild. In 38/43 specimens with available immunohistochemistry, intraepidermal lymphocytes demonstrated a CD4:CD8 ratio ≤1 : 1. Low background levels of the patient's previously identified MF/SS-associated TCR sequence(s) were demonstrated in 20/46 specimens analyzed by high-throughput sequencing of TCR. We conclude that MAR may demonstrate diverse histologic features. Findings that may distinguish MAR from MF/SS include the inverted or normalized CD4:CD8 ratio within intraepidermal lymphocytes and demonstration of absent or nondominant levels of disease-associated TCR sequences. Correlation with the clinical findings and immunohistochemical and molecular characterization of the patient's MF/SS before mogamulizumab, when possible, may facilitate recognition of MAR.

Diagnosis of T-cell lymphoid proliferations of the skin: putting all the pieces together

The spectrum of T-cell lymphoid proliferations of the skin varies from indolent to highly aggressive diseases and therefore an accurate pathological diagnosis is paramount. Integration of clinical, histopathological, immunohistochemical, and molecular findings is of crucial importance in the evaluation of these processes. In this article, we discuss selected situations where difficulty may arise for the pathologist evaluating this type of skin biopsies, such as: the diagnosis of early (patch stage) mycosis fungoides, the distinction of mycosis fungoides with large cell transformation from primary cutaneous anaplastic large cell lymphoma, the recognition of new histopathological patterns of lymphomatoid papulosis and the entities they mimic, the evaluation of primary cutaneous anaplastic large cell lymphoma with expression of markers suggestive of systemic origin (such as ALK), the awareness of the wide range of clinical and pathological presentations of hydroa vacciniforme-like EBV-positive T-cell lymphoproliferative disorders, the evaluation of cases of primary cutaneous γδ T-cell lymphoma showing predominantly epidermotropic pattern of growth, and the correct interpretation of findings seen in indolent proliferations such as primary cutaneous acral CD8-positive T-cell lymphoma and primary cutaneous small/medium size CD4 + T-cell lymphoproliferative disorder.

Cutaneous Lymphomas with Cytotoxic Phenotype

Primary cutaneous cytotoxic lymphomas are T-cell or natural killer-cell lymphomas that express 1 or more cytotoxic markers. These neoplasms constitute a spectrum of diseases. In this review, an overview of clinical, morphologic, and phenotypical features of each subtype is provided. Differential diagnosis is discussed with attention to scenarios in which diagnostic difficulties are most frequently encountered.

Primary cutaneous T-cell lymphoma presenting as mycosis fungoides with a T-/null-cell phenotype: report of two cases

Variations in the clinical and histological presentation of cutaneous T-cell lymphoma (CTCL) can hamper diagnosis. We report two cases of a novel presentation of CTCL characterized by an aberrant immunophenotype with complete loss of pan T-cell antigens including T-cell receptor β chain and showing the clinical and histopathological appearance of erythrodermic and plaque-stage mycosis fungoides.

Cytotoxic T-cell and NK-cell lymphomas: current questions and controversies

The cytotoxic T-cell and natural killer (NK)-cell lymphomas and related disorders are important but relatively rare lymphoid neoplasms that frequently are a challenge for practicing pathologists. This selective review, based on a meeting of the International Lymphoma Study Group, briefly reviews T-cell and NK-cell development and addresses questions related to the importance of precise cell lineage (αβ-type T cell, γδ T cell, or NK cell), the implications of Epstein-Barr virus infection, the significance of anatomic location including nodal disease, and the question of further categorization of enteropathy-associated T-cell lymphomas. Finally, developments subsequent to the 2008 World Health Organization Classification, including the recognition of indolent NK-cell and T-cell disorders of the gastrointestinal tract are presented.