Early nail involvement in mycosis fungoides with rapid systemic progression: rethinking the role of Ki-67: a case report.

BACKGROUND: Mycosis fungoides, the most common cutaneous T-cell lymphoma, typically exhibits a gradual progression. However, aggressive forms with extracutaneous involvement and low proliferative indices may present diagnostic and prognostic challenges. Nail involvement appears to be infrequent and poorly understood, and is often considered a late-stage manifestation. The Ki-67 index, although frequently utilized as an indicator of tumor aggressiveness, may have limitations in specific mycosis fungoides subtypes that appear to be influenced by distinct molecular or immunological pathways.

CASE PRESENTATION: We present a 62-year-old Iranian woman with early stage mycosis fungoides, exhibiting erythematous abdominal plaques, pruritus, and early onset onychodystrophy. Within 4 months, the lesions rapidly progressed to painful plaques affecting the face and intertriginous areas. The initial biopsy revealed features consistent with plaque-stage mycosis fungoides, characterized by CD4 predominance, CD7 deficiency, and a low Ki-67 index (< 5%). Despite low proliferation indices, the disease progressed rapidly. Imaging revealed bilateral lymphadenopathy, and a subsequent biopsy confirmed ongoing disease, with limited CD8 expression, absent B-cell markers, and Ki-67 levels of 1-3%. The treatment regimen comprised methotrexate, interferon-alpha, and psoralen and ultraviolet A therapy. Partial cutaneous response was achieved; however, systemic progression occurred. Laboratory results revealed leukocytosis, elevated lactate dehydrogenase levels, and hepatic impairment. Bone marrow biopsies suggested early dissemination. Peripheral blood flow cytometry and nail biopsy were not conducted. The patient ultimately developed multiorgan failure and was transitioned to palliative care.

CONCLUSION: This case suggests the potential for aggressive mycosis fungoides behavior despite indolent histopathological characteristics. Initial nail involvement might serve as a clinical marker of atypical progression. The limitations of Ki-67 alone suggest the need for comprehensive prognostic models that incorporate molecular biomarkers, such as thymocyte selection-associated high mobility group box, CD30, and T-cell receptor clonality.