Ten Years of Mycosis Fungoides Data Reveal the Cost of Delayed Diagnosis

Mycosis fungoides is the most common form of cutaneous T-cell lymphoma, a rare cancer in which malignant T lymphocytes accumulate in the skin before, in some patients, spreading to lymph nodes and blood. Because its earliest lesions resemble eczema, psoriasis and other inflammatory dermatoses, patients routinely wait years for a definitive answer. A new research letter published in the Archives of Dermatological Research by Burhan Engin of Istanbul University-Cerrahpaşa, Gurbuz Yildirim of Bağcılar Training and Research Hospital, and Yusuf Can Erkoc adds a decade of single-centre clinical experience to the limited real-world evidence base for this disease, documenting how patients present, how they are staged and treated, and how they fare over long-term follow-up.

The study, conducted at Cerrahpaşa Medical Faculty in Istanbul and approved by the institutional review board there, retrospectively evaluated the clinical and follow-up records of patients diagnosed and managed at the centre over a ten-year period. Engin performed the skin biopsies, diagnosed and treated the patients, and led the manuscript; Yildirim assisted with follow-up and drafted the text; Erkoc classified treatments and staging and analysed the data. The work was carried out in accordance with the Declaration of Helsinki, and the authors report no conflicts of interest. As is typical for retrospective cohort analyses of rare lymphomas, the value of the dataset lies less in dramatic new findings than in the granular picture it paints of how one busy dermatology service handles a diagnostically treacherous disease over time.

Technically, mycosis fungoides belongs to the primary cutaneous lymphomas, a family of extranodal non-Hodgkin lymphomas that arise in the skin rather than in lymphoid organs. The current diagnostic framework is anchored by the 2018 update of the WHO-EORTC classification, which separates indolent entities such as early-stage mycosis fungoides from aggressive ones such as Sézary syndrome, the leukemic variant characterised by widespread erythroderma, circulating malignant T cells and a markedly worse prognosis. The International Consensus Classification of mature lymphoid neoplasms, published in 2022, further refined this landscape. Within that framework, mycosis fungoides follows a characteristic clinical course: patch-stage lesions progress to plaques, then potentially to tumours, and in a minority of patients to visceral involvement. Most patients, however, never advance beyond the early stages, which is why accurate staging at diagnosis is the single most important prognostic exercise.

That staging depends on a synthesis of clinical, histopathological and, where indicated, molecular data. Skin biopsies are examined for epidermotropism, the migration of atypical T lymphocytes into the epidermis, and for the formation of Pautrier microabscesses, small clusters of these cells that are highly characteristic though not always present. T-cell receptor gene rearrangement studies can demonstrate clonality, distinguishing a malignant population from a reactive infiltrate, but early lesions may lack convincing clonal evidence, forcing clinicians to repeat biopsies over months or years. Blood tests assess for Sézary cells, and in advanced cases, imaging and lymph node biopsy complete the tumour-node-metastasis-blood staging algorithm. The Istanbul study reflects this layered diagnostic process, with the corresponding author personally performing and interpreting the skin biopsies that anchored each patient’s diagnosis.

One of the best-documented problems in the field is diagnostic delay. A frequently cited Danish study by Skov and Gniadecki found that the histopathological diagnosis of mycosis fungoides is often delayed, with patients carrying the disease for years before a biopsy confirms it, partly because early histology is subtle and mimics spongiotic or psoriasiform dermatitis. Every additional year of misdiagnosis represents deferred access to skin-directed therapy and prolonged uncertainty for the patient. A ten-year single-centre dataset is precisely the kind of evidence that quantifies this burden in a specific population, and the Turkish authors frame their work explicitly as an evaluation of clinical and follow-up data, the raw material from which such delays and their consequences can be measured.

Treatment for mycosis fungoides is stage-adapted, and the European Organisation for Research and Treatment of Cancer issued updated consensus recommendations in 2023 that codify the current hierarchy. Early-stage disease is managed with skin-directed therapies: topical corticosteroids and retinoids, phototherapy with narrowband UVB for patches and thin plaques, psoralen plus ultraviolet A for thicker lesions, and localised radiotherapy or total skin electron beam therapy for more extensive or refractory cutaneous involvement. Advanced disease adds systemic options, including interferon-alpha, retinoids such as bexarotene, histone deacetylase inhibitors, antibody-based therapies and, in selected cases, allogeneic stem cell transplantation, the only treatment with potential for durable cure. Combination approaches, pairing a skin-directed modality with a systemic agent, are common in tumour-stage disease. The Istanbul team’s classification of treatments and staging across their cohort maps directly onto this algorithm and illustrates how a high-volume centre deploys it in practice.

Single-centre cohort studies of this kind occupy an important niche in rare-disease research. Randomised trials in mycosis fungoides are difficult to power because the disease is uncommon and its early stages progress slowly, so much of what is known about natural history, treatment patterns and outcomes comes from institutional series accumulated over years or decades. Previous examples include the retrospective analysis of 133 cutaneous lymphoma patients from a single Japanese centre published by Fujita and colleagues, which similarly documented presentation patterns and outcomes over a multi-year window. The Turkish dataset joins this tradition, offering a Mediterranean and Middle Eastern patient population whose demographic profile, referral pathways and treatment access may differ meaningfully from the Northern European and Japanese cohorts that dominate the literature.

The follow-up dimension of the study deserves particular emphasis. Mycosis fungoides can smoulder for decades, and late relapse or transformation to a more aggressive large-cell phenotype can occur years after apparent stability. Longitudinal data from a single centre, where patients are followed by the same diagnostic and therapeutic team, reduce the heterogeneity that plagues multi-site registries, though they also introduce the limitations inherent to retrospective design: reliance on recorded notes, potential loss of patients to follow-up, and the absence of a standardised prospective protocol. The authors’ explicit contribution statement, detailing who diagnosed, biopsied, treated, staged and analysed, underscores the continuity of care that gives such datasets their internal consistency.

For the wider scientific audience, the significance of this research letter lies in what it represents rather than in any single headline number. It demonstrates that cutaneous lymphoma care in Turkey is organised around internationally recognised classification and treatment frameworks, that long-term follow-up is feasible in a public hospital dermatology service, and that the diagnostic bottleneck remains the central challenge of the disease. It also reinforces a message that dermatologists have been repeating for years: persistent, treatment-resistant or unusually distributed skin lesions in adults warrant a low threshold for biopsy and, when histology is equivocal, serial re-biopsy and specialist referral. Earlier recognition will not change the biology of mycosis fungoides, but it moves patients into appropriate surveillance and stage-appropriate therapy sooner, which matters for quality of life and, in the minority who progress, for survival.

The study is available as a research letter in volume 318 of the Archives of Dermatological Research, and its full clinical tables and figures are accessible through the journal. As genomic profiling, targeted immunotherapies and biomarker-driven risk stratification enter the cutaneous lymphoma field, datasets like this one, grounded in a decade of unbroken clinical contact with patients, will serve as the historical baseline against which the next generation of diagnostics and treatments is judged. For now, the Istanbul experience stands as a reminder that in rare lymphomas of the skin, the most powerful clinical instrument remains the patient chart kept faithfully over many years.

Subject of Research: A 10-year single-centre retrospective evaluation of clinical presentation, staging, treatment and follow-up in patients with mycosis fungoides, the most common cutaneous T-cell lymphoma.

Article Title: Evaluation of clinical and follow-up data in patients with mycosis fungoides: a 10-year single-centre experience

Article References: Engin, B., Yildirim, G., & Erkoc, Y. C. (2026). Evaluation of clinical and follow-up data in patients with mycosis fungoides: a 10-year single-centre experience. Archives of Dermatological Research, 318(1), Article 449. https://doi.org/10.1007/s00403-026-04943-7

Image Credits: AI Generated

DOI: 10.1007/s00403-026-04943-7

Keywords: mycosis fungoides, cutaneous T-cell lymphoma, dermatology, WHO-EORTC classification, diagnostic delay, skin biopsy, staging, skin-directed therapy, Sézary syndrome, retrospective cohort study, Istanbul, long-term follow-up