Management of the Cutaneous Peripheral T-Cell Lymphomas: When Subtypes Matter

Primary Cutaneous Peripheral T-Cell Lymphoma Not Otherwise Specified: A Rapidly Progressive Variant of Cutaneous T-Cell Lymphoma

Primary Cutaneous Peripheral T-Cell Lymphoma NOS (PTL-NOS) is a rare, progressive, fatal dermatologic disease that presents with features similar to many common benign plaque-like skin conditions, making recognition of its distinguishing features critical for early diagnosis and treatment (Bolognia et al., 2008). A 78-year-old woman presented to ambulatory care with a single 5 cm nodule on her shoulder that had developed rapidly over 1-2 weeks. Examination was suspicious for malignancy and a biopsy was performed. Biopsy results demonstrated CD4 positivity, consistent with Mycosis Fungoides with coexpression of CD5, CD47, and CD7. Within three months her cancer had progressed into diffuse lesions spanning her entire body. As rapid progression is usually uncharacteristic of Mycosis Fungoides, her diagnosis was amended to PTL-NOS. Cutaneous T-Cell Lymphoma (CTCL) should be suspected in patients with patches, plaques, erythroderma, or papules that persist or multiply despite conservative treatment. Singular biopsies are often nondiagnostic, requiring a high degree of suspicion if there is deviation from the anticipated clinical course. Multiple biopsies are often necessary to make the diagnosis. Physicians caring for patients with rapidly progressive, nonspecific dermatoses with features described above should keep more uncommon forms of CTCL in mind and refer for early biopsy.

CD68 expression is a discriminative feature of indolent cutaneous CD8-positive lymphoid proliferation and distinguishes this lymphoma subtype from other CD8-positive cutaneous lymphomas

BACKGROUND

Indolent cutaneous CD8+ lymphoid proliferation is a recently described rare entity among cutaneous T-cell lymphomas that typically presents with solitary skin lesions at acral sites. Separation from otherwise aggressive T-cell lymphomas bearing a cytotoxic CD8+ phenotype is fundamental to avoid unnecessary harmful treatment. However, up to now, no reliable discriminative marker has been identified.

OBJECTIVES

Motivated by these diagnostic quandaries, we have analyzed a large series of archived formalin-fixed paraffin-embedded (FFPE) specimens of atypical CD8+ cutaneous infiltrates with clear-cut diagnosis and clinical follow-up (n = 44) including five cases of indolent CD8+ lymphoid proliferation by using immunohistochemistry with the aim of obtaining markers predictive of subtype assignment.

RESULTS

We identified exclusive expression of CD68 by lymphoma cells within the subgroup of indolent CD8+ lymphoid proliferation (5/5 cases). Specific CD68 expression in this entity was confirmed by the application of several monoclonal antibodies (KP1, PG-M1, KiM1P) against the CD68 molecule available for FFPE tissue. In contrast, none of the infiltrates of the other CD8+ cutaneous lymphoma entities stained positive for CD68 (0/39).

CONCLUSIONS

Based on these observations, we suggest CD68 as a new discriminative marker which is helpful in distinguishing indolent CD8+ lymphoid proliferation from other CD8+ cutaneous lymphomas in ambiguous cases.

Pathology of T-cell lymphomas: diagnosis and biomarker discovery

T-cell lymphomas are a group of predominantly rare hematologic malignancies that tend to recapitulate different stages of T-cell development, in a similar way that B-cell lymphomas do. As opposed to B-cell lymphomas, the understanding of the biology and the classification of T-cell lymphomas are somewhat rudimentary, and numerous entities are still included as 'provisional categories' in the World Health Classification of hematolopoietic malignancies. A relevant and useful classification of these disorders have been difficult to accomplish because of the rarity nature of them, the relative lack of understanding of the molecular pathogenesis, and their morphological and immunophenotypical complexity. Overall, T-cell lymphomas represent only 15 % of all non-Hodgkin lymphomas. This review is focused on addressing the current status of the categories of mature T-cell leukemias and lymphomas (nodal and extranodal) using an approach that incorporates histopathology, immunophenotype, and molecular understanding of the nature of these disorders, using the same philosophy of the most recent revised WHO classification of hematopoietic malignancies.

Extrafacial indolent CD8-positive cutaneous lymphoid proliferation with unusual symmetrical presentation involving both feet

Indolent CD8+ cutaneous lymphoid proliferation represents a recently described entity among cutaneous T-cell lymphomas that typically presents with solitary skin lesions on the face or at acral sites and usually follows an indolent clinical course. Histopathologically, this entity is characterized by a dense dermal infiltrate of non-epidermotropic, small- to medium-sized pleomorphic CD8+ T-cells of the non-activated cytotoxic phenotype showing a clear-cut grenz zone and a low proliferation index. Distinction from otherwise aggressive T-cell lymphomas bearing a cytotoxic CD8+ phenotype is fundamental. We herein present an unusual case of indolent CD8+ cutaneous lymphoid proliferation presenting in bilateral symmetrical distribution on both feet and lacking the otherwise described grenz zone. Our case widens the spectrum of possible clinical and histomorphological variations of this entity. Taking into account the distinctive and unique clinical and microscopic features of all hitherto published cases of indolent CD8+ cutaneous lymphoid proliferation we suppose that this lymphoma subtype has to be included as a new and distinct entity in the World Health Organisation (WHO)-/European Organisation for Research and Treatment of Cancer (EORTC)-classification of cutaneous lymphomas.