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Lymphoma - Non B cell neoplasms

T/NK cell disorders

Primary cutaneous CD4+ small/medium T cell lymphoma


Reviewer: Dragos Luca, M.D. (see Reviewers page)
Revised: 31 October 2011, last major update August 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Definition
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● A cutaneous T cell lymphoma characterized by a predominance of small to medium-sized CD4+ pleomorphic T cells without evidence of patches and plaques typical of mycosis fungoides (provisional entity, WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 4th Edition, Lyon 2008)

Terminology
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● Cutaneous nodular proliferation of pleomorphic T-lymphocytes of undetermined significance

Epidemiology
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● Rare, 2% of all cutaneous T cell lymphomas

Sites
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● Solitary plaque or nodule on face, neck, upper trunk
● Lower extremity involvement is rare

Clinical features
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● Usually asymptomatic; only clinical feature is a solitary skin lesion
● Rarely large tumors or multiple skin lesions

Case reports
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● Associated with annular elastolytic giant cell granuloma (Br J Dermatol 2009;160:1126)
● Coexisting with myelodysplastic syndrome (Dermatol Ther 2010;23:676)

Treatment and prognosis
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● Favorable prognosis, 80% 5-year survival
● Solitary skin lesions have an excellent prognosis (surgical excision or radiotherapy), multiple/large lesions may be more aggressive

Postulated normal counterpart
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● Skin homing CD4+ T cell

Gross description
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● Solitary plaque or nodule (more favorable) or multiple or large lesions (more aggressive)

Gross images
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Various images

Micro description
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● Dense, diffuse or nodular dermal infiltrate with tendency to subcutaneous involvement
● May have focal epidermotropism but if more than that, consider mycosis fungoides
● Predominantly small/medium-sized pleomorphic T cells sometimes with a small proportion (<30%) of large pleomorphic cells
● May have admixed reactive lymphocytes, histiocytes, eosinophils, plasma cells

Micro images
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Various images

Positive stains
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● CD3, CD4

Negative stains
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● CD8, CD30, cytotoxic markers, loss of a pan-T cell marker, EBV

Genetics and Molecular
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● Clonal rearrangements of the TCR genes
● No specific cytogenetic abnormality

Molecular images
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Various images

Differential diagnosis
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● Reactive lymphoid infiltrate of the skin: also called pseudolymphoma or cutaneous lymphoid hyperplasia; no clonal TCR gene rearrangements, no loss of a pan-T cell marker

Additional references
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● Review articles: Mod Pathol 2008;21:708, J Clin Oncol 2008;26:3364, Am J Dermatopathol 2009;31:317, Am J Surg Pathol 2004;28:719

End of Lymphoma - Non B cell neoplasms > T/NK cell disorders > Primary cutaneous CD4+ small/medium T cell lymphoma


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