Cutaneous T-cell lymphoma, NK-cell lymphoma, and myeloid leukemia

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Cutaneous T-cell lymphoma, NK-cell lymphoma, and myeloid leukemia

David J. DiCaudo

Cutaneous T-cell lymphoma and NK-cell lymphoma

Mycosis fungoides

Patch stage

• Lymphocytes “line up” along the dermal–epidermal junction (simulates vacuolar interface dermatitis, with a “lymphocyte in every hole”)

• Large dark lymphocytes with irregular nuclear contours and perinuclear haloes (“lump of coal on a pillow”)

• Pautrier’s microabscesses (intraepidermal clusters of atypical lymphocytes, larger than the benign recruited dermal lymphocytes)

• Mild band-like infiltrate in superficial dermis

• Sclerosis of the papillary dermis

• Eosinophils and necrotic keratinocytes are rarely present

Table 24-1

Primary cutaneous T-cell lymphomas, NK-cell lymphomas, and precursor hematologic neoplasm in the 2008 WHO classification

Mature T-cell and NK-cell neoplasms

Mycosis fungoides

Mycosis fungoides variants and subtypes

Pagetoid reticulosis

Folliculotropic mycosis fungoides

Granulomatous slack skin

Sézary syndrome

Adult T-cell leukemia/lymphoma

Primary cutaneous CD30+ T-cell lymphoproliferative disorders

Lymphomatoid papulosis

Primary cutaneous anaplastic large cell lymphoma

Subcutaneous panniculitis-like T-cell lymphoma

Extranodal NK/T-cell lymphoma, nasal type

Primary cutaneous peripheral T-cell lymphoma, rare subtypes

Primary cutaneous aggressive epidermotropic CD8+ cytotoxic T-cell lymphoma ^a

Primary cutaneous gamma–delta T-cell lymphoma

Primary cutaneous CD4+ small/medium T-cell lymphoma ^a

Hydroa vacciniforme-like lymphoma

Precursor hematologic neoplasm

Blastic plasmacytoid dendritic cell neoplasm (CD4+/CD56+ hematodermic neoplasm)

^a Provisional entities.

Adapted from WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 4th edn. Lyon, France: IARC; 2008.

Mycosis fungoides (MF) is the most common type of cutaneous lymphoma. In most cases, the disease is indolent and slowly progressive over a period of years or decades. Three main stages of the lymphoma are recognized: patch, plaque, and tumor stages. In the patch stage of mycosis fungoides, patients typically present with broad pink or tan oval-shaped patches with a predilection for the bathing trunk area. The patches may be asymptomatic or pruritic. Both clinically and histopathologically, distinction from eczematous dermatitis is sometimes difficult in the earliest stages of the lymphoma. In the evaluation of patch stage mycosis fungoides, multiple shave biopsies are often helpful, since the shave technique provides a broad area of epidermis for examination. The typical immunophenotype is CD3+, CD4+, CD8−, CD30−. Aberrant immunophenotypes (with loss of normal T-cell markers, such as CD7) can frequently be demonstrated. Clonal rearrangement of the T-cell receptor gene is helpful in supporting the diagnosis, although the earliest cases may sometimes not have a detectable clone.

Differential Diagnosis

• Dermatitis generally has more spongiosis and fewer intraepidermal lymphocytes

• Lichenoid drug eruption typically has more apoptotic keratinocytes

• Lymphomatoid drug eruption may look nearly identical. Pautrier’s microabscesses favor mycosis fungoides

Fig 24-1 Patch stage mycosis fungoides

Fig 24-2 Patch stage mycosis fungoides

Plaque stage

• Like patch stage, but with a denser, band-like infiltrate in the upper dermis

• Atypical lymphocytes present in the dermal band

Fig 24-3 Plaque stage mycosis fungoides

Tumor stage

• Dense, nodular lymphocytic infiltrate in the superficial and deep dermis

• Many atypical lymphocytes present in the dermal infiltrate

• Transformation to large-sized lymphocytes in some cases

• Acquisition of CD30 expression in some cases

• Loss of epidermotropism with progression

Over time, patients with mycosis fungoides may progress to develop thicker plaques and tumors. Whereas patch stage mycosis fungoides is usually associated with long survival, the prognosis is poor for those patients who progress to tumor stage.

Fig 24-4 Tumor stage mycosis fungoides

Fig 24-5 Tumor stage mycosis fungoides

Fig 24-6 Tumor stage mycosis fungoides

Pagetoid reticulosis variant

• Solitary or multiple patches or plaques on distal extremities

• Atypical large lymphocytes extensively infiltrating the epidermis

• CD4+ CD8− or CD4− CD8+

• Small reactive lymphocytes in papillary dermis

The term pagetoid reticulosis is now limited to the Woringer–Kolopp type, which presents as one or several patches or plaques on the distal extremities. This type of lymphoma is associated with an excellent prognosis. The disseminated Ketron–Goodman type of pagetoid reticulosis has been reclassified into several other types of cutaneous T-cell lymphoma.

Fig 24-7 Pagetoid reticulosis variant of mycosis fungoides

Folliculotropic variant

• Atypical lymphocytes infiltrate the follicular epithelium

• Basaloid induction and hyperplasia of follicular epithelium

• Eosinophils common

• Follicular mucinosis (pools of mucin in the follicular epithelium)

• Epidermis usually spared

• CD3+ CD4+ CD8− in most cases

The folliculotropic variant of mycosis fungoides presents with follicular papules and boggy plaques, most frequently involving the head and neck. Follicular mucinosis is often associated. This variant of mycosis fungoides is sometimes associated with a more rapidly progressive clinical course.

Fig 24-8 Folliculotropic variant of mycosis fungoides

Granulomatous slack skin

Granulomatous slack skin syndrome is an extremely rare variant of mycosis fungoides with a slowly progressive clinical course. The clinical presentation is striking. In fully developed cases, massive folds of skin extend from flexural areas, such as the axillae or groin. An association with nodal Hodgkin lymphoma has been documented in multiple cases.

Fig 24-9 Granulomatous slack skin variant of mycosis fungoides

Fig 24-10 Granulomatous slack skin variant of mycosis fungoides

Sézary syndrome

Although previously believed to be a leukemic variant of mycosis fungoides, Sézary syndrome is now considered to originate from a different subset of T cells (central memory T cell in Sézary syndrome versus skin resident memory T cell in mycosis fungoides). In contrast to mycosis fungoides, Sézary syndrome has a rapidly progressive clinical course and a poor prognosis. The diagnosis is confirmed by evaluation of the peripheral blood. Skin biopsy is sometimes useful in demonstrating a histopathologic pattern similar to mycosis fungoides. It should be recognized, however, that skin biopsy findings may be non-diagnostic in some cases of Sézary syndrome. In an erythrodermic patient, non-specific biopsy findings (such as spongiotic dermatitis) do not exclude the diagnosis. It is important to evaluate the peripheral blood if there is clinical suspicion for Sézary syndrome.

Fig 24-11 Sézary syndrome

Adult T-cell leukemia/lymphoma (ATCLL)

Adult T-cell leukemia/lymphoma is remarkable for its well-established viral etiology, i.e. human T-cell leukemia virus type 1 (HTLV-1

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