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Pathological Anatomy · Hematopoietic System Diseases

Cutaneous lymphomas

Lymphomata cutis

Primary cutaneous lymphomas are a group of malignant lymphoid neoplasms that develop primarily in the skin without evidence of extracutaneous involvement at the time of diagnosis. In the majority of cases (approximately 60–65%), they are of T-cell origin.

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T-cell frequency:60–65% of all primary cutaneous lymphomas are of T-cell origin.
Mycosis fungoidesThe most common form, accounting for 50% of all primary cutaneous lymphomas.
B-cell lymphomasAccount for 20–25% of all cutaneous lymphoproliferative disorders.
Sézary syndromeA leukemic form of T-cell lymphoma characterized by a classic triad of features.
3 min readFor medical studentsUpdated Sep 25, 2026
Material prepared by WhiteCoat Pro editorial team based on platform study guidesReviewed by medical editor: Aulov A. A., general practitioner · 09/24/2026

T-cell lymphomas

This is the most significant group of skin neoplasms. The most frequent is Mycosis fungoides. As the disease progresses, the infiltrate becomes diffuse and can invade the subcutaneous adipose tissue. A characteristic morphological feature is cerebriform lymphocytes — cells with convoluted nuclei resembling the surface of the brain.

Transformation and prognosis

In late stages, mycosis fungoides may undergo large-cell transformation. This is a critical point in pathogenesis, as transition to large-cell lymphoma significantly worsens the patient's prognosis.

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Sézary syndrome

This is a specific leukemic variant of T-cell lymphoma. Diagnosis requires the presence of the classic triad:

  1. Erythroderma (generalized skin redness).
  2. Lymphadenopathy (enlarged lymph nodes).
  3. The presence of neoplastic T-lymphocytes, known as Sézary cells, in the skin and peripheral blood.

B-cell lymphomas

B-cell variants represent distinct clinicopathological subtypes of extranodal lymphomas. They are less common than T-cell lymphomas, accounting for approximately a quarter of all cutaneous lymphoproliferative processes.

Briefly: answers to topical questions

What are the three consecutive classical clinical stages of mycosis fungoides?

In the classic variant of mycosis fungoides (Mycosis fungoides), the disease sequentially passes through three clinical stages.

  • Patch — an erythematous stage characterized by epidermotropic superficial small-focal perivascular infiltrates.
  • Plaque — a stage characterized by an epidermotropic dense band-like infiltrate in the upper dermis.
  • Tumor — a stage featuring a dense focal or diffuse infiltrate that involves the entire dermis and penetrates into the subcutaneous adipose tissue.

What are Pautrier microabscesses and in which layer of the skin do they localize?

Pautrier microabscesses are intraepidermal accumulations of atypical lymphocytes. They localize in the epidermis of the skin. This feature is characteristic of the plaque stage of mycosis fungoides and is one of the main pathomorphological diagnostic criteria for the disease.

What is the exact immunophenotype (CD markers) of tumor cells in mycosis fungoides?

In the most frequent classic variant of mycosis fungoides, tumor cells have the immunophenotype of mature memory cells (α/β T-helper cells). The main immunophenotype of infiltrating cells includes the following markers: βF1+, CD2+, CD3+, CD4+, CD5+, CD7+, CD8-, CD45RO+. Furthermore, a loss of expression of the pan-T-cell marker CD7 by more than 10% of lymphocytes is characteristic. In late stages of the disease, complete or partial loss of expression of pan-T-cell antigens CD2, CD3, CD5, and CD7 can be observed, as well as an increased CD4/CD8 ratio of more than 8/1.

How to memorize

Sézary triad: E-L-C (Erythroderma, Lymphadenopathy, Circulating Sézary cells).

Class and exam questions

What are cerebriform lymphocytes?

These are pathological lymphocytes with convoluted nuclei, which constitute a key cellular component of the infiltrate in mycosis fungoides.

How does Sézary syndrome differ from conventional mycosis fungoides?

Sézary syndrome is a leukemic variant in which tumor cells enter the peripheral blood, accompanied by erythroderma and lymphadenopathy.

Which transformation is the most dangerous in mycosis fungoides?

Transition to large-cell lymphoma, which significantly worsens the prognosis of the disease.

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What else to study on this topic

  • Differential diagnosis between T- and B-cell cutaneous lymphomas.
  • Staging of mycosis fungoides using the TNM system.
  • Morphological features of Sézary cells on electron microscopy.
  • The role of immunohistochemical examination in typing cutaneous lymphomas.
  • Histiocytic and dendritic cell neoplasms as rare forms of lymphoproliferative disorders.

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