Mycosis fungoides, Sezary syndrome, Peripheral T-cell lymphoma

A) Peripheral T-Cell Lymphoma (PTCL)

Overview

• Heterogeneous and aggressive group of tumors with T-/NK cell phenotype
• Most patients are adults
• Usually extra-nodal manifestation, but nodal involvement also occurs

Clinical features

• B symptoms (common):
  • Fever with no obvious cause
  • Drenching night sweats
  • Unexplained weight loss
• Poor response to chemotherapy
• 5-year survival: ~30%

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B) Anaplastic Large Cell Lymphoma (ALCL)

Overview

• Aggressive type of T-/NK cell lymphoma
• Neoplastic cells are large, underdeveloped, and very abnormal (= “anaplastic”)

Types of ALCL

• ALK-positive ALCL: abnormal T-cells produce ALK (anaplastic lymphoma kinase) protein; high-grade; better prognosis
• ALK-negative ALCL: ALK protein absent; also high-grade; worse prognosis
• Breast implant-associated ALCL: rare; develops in breast tissue around implants; not a breast cancer
• Primary cutaneous ALCL: low-grade T-cell lymphoma; develops in skin

Clinical

• Painless lymphadenopathy: neck, armpit, groin
• B symptoms may occur

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C) Mycosis Fungoides & Sézary Syndrome

Overview

Both are cutaneous T-cell lymphomas composed of neoplastic CD4+ T-cells found in the skin.

• Indolent lymphoma with slow progression

Mycosis fungoides

Progresses through 3 stages on skin:

1. Patches → ill-defined; minimal lymphocytic infiltrate
2. Plaques → dense lymphoid infiltrate in upper dermis
3. Tumors → loss of epidermotropism; raised nodules

Histology:

• Infiltration of epidermis and upper dermis by neoplastic T-cells
• Cells: small to medium lymphocytes with cerebriform nuclei
• With progression: nodal and visceral dissemination

Sézary syndrome

• Less common; affects both skin and blood
• Characterized by: swollen lymph nodes + very red, itchy rash
• Sézary cells: cerebriform-shaped T-cells found in both skin and peripheral blood

💡 High-yield: PTCL = aggressive T-/NK tumors; poor chemo response; 5-yr survival ~30%; B symptoms. ALCL = large anaplastic T-cells; ALK+ = better prognosis. Mycosis fungoides = cutaneous CD4+ T-cell; stages: patch → plaque → tumor; cerebriform nuclei. Sézary = skin + blood involvement.