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Skin - Nonmelanocytic tumors

Lymphoma and related disorders

Mycosis fungoides

Reviewer: Christopher Hale, M.D. (see Reviewers page)
Revised: 16 July 2012, last major update July 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.

General
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● Most common primary cutaneous T cell lymphoma
● Usually elderly or other adults
● May arise from progression of large plaque psoriasis
● Usually protracted clinical course over years
● By definition, are negative for HIV1, HIV2, HTLV

Sézary syndrome:
● Peripheral blood involvement by cerebroid cells with PAS+ granules, lymphadenopathy, diffuse erythema and scaling of entire body surface
● Usually less epidermotropism
● Lymph nodes may have tumor cells or dermatopathic lymphadenitis (no atypical T cells, normal architecture, no clonality)

Poor prognostic factors:
● Generalized plaques/tumors, diffuse erythema, lymphadenopathy
● 50% have nodal or visceral involvement that may resemble large cell lymphoma
● Sepsis is a common terminal complication

Treatment for skin limited disease:
● Total skin electron beam irradiation, topical chemotherapy, PUVA

Case reports
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● 52 year old man with psoriasiform acral plaques (Case Rep Dermatol. 2009 Oct 27;1:60)
● 68 year old Caucasian man with erythematous plaques and bullae (J Med Case Reports 2010;4:78)

Clinical images
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Various images

Micro images
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Various images

Molecular
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● Clonal proliferation of mature CD4+ epidermotropic lymphocytes
● Low CD8/CD3 ratio in epidermal tumor cells (Mod Pathol 2003;16:857)

Differential diagnosis
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● Drug reaction
● Inflammatory dermatoses (resemble early mycosis fungoides)

Premycotic (patch) stage

General
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● Usually indolent course

Gross description
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● Erythematous, scaly and pruritic skin

Micro description
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● Chronic non-specific dermatitis with psoriasiform changes in epidermis: often associated changes of lichen simplex chronicus due to repeated rubbing

Mycotic stage

Gross description
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● Infiltrative plaques

Micro description
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● Dermal polymorphous infiltrate of atypical lymphocytes with cerebriform nuclei alone or clustered in epidermis and in small sheets in dermis
● Also Pautrier microabscesses, palisading along epidermal basal layer, tumor infiltrates around hair follicles, variable follicular mucinosis

Micro images
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Low CD8 expression (B) compared to inflammatory dermatoses (D)

Tumorous stage

General
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Treatment:
● Systemic chemotherapy

Micro description
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● Dense dermal infiltrates of atypical T cells with cerebroid nuclei (with thin sections)
● May have reactive B cell component also

Positive stains
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● CD4 (usually)

Negative stains
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● CD2, CD3, CD5, CD7

Molecular
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● T cell receptor gene clonality

Differential diagnosis
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● Acute or chronic dermatitis with cerebroid cells

End of Skin - Nonmelanocytic tumors > Lymphoma and related disorders > Mycosis fungoides

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