CD20+ Mycosis Fungoides

Aberrant expression in lymphoma, a diagnostic pitfall

One of the major difficulties in practical hematopathology is to accurately assign cell lineage and thus ensure proper classification of lymphomas. The lineage-specific markers of lymphoma are detected by immunohistochemistry or flow cytometry immunophenotypic methods. However, aberrant gain or loss of these markers is occasionally encountered during daily practice, which often creates diagnostic challenges. In addition, lymphoma may aberrantly express non-hematopoietic markers, and vice versa. This review article provides an overview of aberrant gain of expression of lineage-associated antigens in mature lymphoid neoplasms, including recommendations to avoid diagnostic pitfalls and ultimately to reach accurate diagnoses.

A comprehensive study on aberrant CD20+ mycosis fungoides: clinical and prognostic insights

BACKGROUND

As the majority of T-cell lymphomas lack CD20 expression, cases of mycosis fungoides (MF) exhibiting aberrant CD20 expression are exceedingly uncommon.

OBJECTIVES

To comprehensively evaluate the clinical, histopathological and prognostic features of seven patients diagnosed with CD20+ MF.

METHODS

This retrospective study involved seven cases of MF with aberrant CD20 expression. The study provides details of demographics, clinical features, histopathology and treatment outcomes. Key timepoints include initial diagnosis of MF, detection of CD20 expression and follow-up, with a mean follow-up of 46 months.

RESULTS

Aberrant CD20+ MF was diagnosed at an average age of 58.6 years, approximately 5.6 years after the first MF diagnosis. Following CD20 detection, patients presented with advanced disease stages, requiring treatments such as chemotherapy, brentuximab vedotin and allogeneic haematopoietic stem cell transplantation. Four patients died from lymphoma, with an average survival time of 52 months.

CONCLUSIONS

Aberrant CD20 expression in MF is rare but indicates a progressive course associated with poor prognosis. This often requires systemic chemotherapy and, in certain instances, allogeneic haematopoietic stem cell transplantation. This study provides important insights into the clinical attributes, disease progression and treatment options for patients with MF with aberrant CD20 expression. Further research is necessary to validate the effectiveness of emerging therapies and enhance our understanding of the underlying mechanisms and prognostic determinants specific to this unique MF subgroup.

Primary Cutaneous Anaplastic Large-Cell Lymphoma With Aberrant CD20 Expression: Case Report and Review of the Literature

ABSTRACT

Cutaneous CD20 + T-cell lymphomas are exceedingly rare. Differentiating cases of T-cell lymphoma with aberrant expression of the B-cell marker CD20 from B-cell lymphoma may be associated with misdiagnosis or delays in diagnosis. We report, to the authors' knowledge, the first case of CD20 + primary cutaneous anaplastic large-cell lymphoma and review the literature to characterize published cases of CD20 + cutaneous T-cell lymphoma (n = 40). There is no accepted explanation for this phenomenon; however, it is suspected that these cases may be due to neoplastic transformation of CD20 + T cells or that CD20 may represent a T-cell activation marker. Expression of CD20 may have clinical significance in prognostication and consideration of treatment options with anti-CD20 therapies such as rituximab.

Gamma-Delta and CD20 Mycosis Fungoides: Two Cases Uncovered by Broad-Spectrum Immunostaining

ABSTRACT

Mycosis fungoides (MF) expresses T-cell markers and the alpha-beta T-cell receptor (TCR) complex. Here, we describe a case of MF with dual expression of TCR delta and TCR beta and a case of MF expressing the B-cell marker CD20. Both anomalies were detected after we instituted a broad-spectrum immunostaining panel for cutaneous T-cell lymphomas. These findings suggest anomalous immunophenotypes may be more common in MF than previously appreciated. Histopathologists should be aware of unexpected malleability in the immunophenotype of MF to avoid confusion with other subtypes of cutaneous lymphoma. Further research into the prevalence and significance of CD20 and TCR-delta expression in MF is encouraged.

Outcomes and prognostic factors in canine epitheliotropic and nonepitheliotropic cutaneous T-cell lymphomas

Canine cutaneous lymphoma is an uncommon lymphoma in dogs. Most canine cutaneous lymphoma cases have a T-cell origin. Canine cutaneous T-cell lymphoma (CTCL) is classified into epitheliotropic and nonepitheliotropic cutaneous lymphomas, and each type of lymphoma is subclassified into several histological subtypes. Limited information is available regarding the prognostic significance of clinical variables and histopathological subtypes in dogs with CTCL. This retrospective study aimed to investigate the influence of clinical variables and histopathological subtypes on the prognosis of dogs with CTCL. Forty-six dogs diagnosed with CTCL by histopathological examination were included. Histopathological specimens were reexamined and classified into CTCL subtypes. The influence of the type of skin lesion, histopathological subtype, haematological examination results and treatment response on the overall survival time (OS) was examined. Thirty-one dogs were diagnosed with epitheliotropic CTCL (mycosis fungoides in 28 dogs; pagetoid reticulosis in 3 dogs) and 15 dogs were diagnosed with nonepitheliotropic CTCL (anaplastic large T-cell lymphoma in 6 dogs; peripheral T-cell lymphoma, not otherwise specified, in 9 dogs). The OS of dogs diagnosed with epitheliotropic CTCL (141 days) was significantly shorter than that of dogs diagnosed with nonepitheliotropic CTCL (374 days). As clinical variables, the presence of neoplastic lymphocytes in peripheral blood, thrombocytopenia and initial chemotherapeutic response was related to prognosis. Our results demonstrated that histopathological subtype and several clinical variables were found to influence the prognosis of dogs with CTCL.

Prevalence of CD20+ cutaneous epitheliotropic T-cell lymphoma in dogs: a retrospective analysis of 24 cases (2011-2018) in the USA

BACKGROUND

Limited information is known about the baseline frequency of canine CD20 positive (⁺ ) cutaneous epitheliotropic T-cell lymphoma. A single canine case report has been published.

OBJECTIVES

To characterize the baseline frequency of CD20⁺ staining in cases of canine cutaneous epitheliotropic T-cell lymphoma; to assess its values as a prognostic indicator.

ANIMALS

Skin biopsies from 24 client-owned animals diagnosed with cutaneous epitheliotropic lymphoma were assessed.

METHODS AND MATERIALS

A retrospective review of medical records from 2011 to 2018. Clinical histories and previous histological and immunohistochemical slides were collected from 24 dogs and additional immunohistochemical staining was performed as needed to assess cases of cutaneous epitheliotropic T-cell lymphoma for CD3, CD20, CD79a and PAX5 staining characteristics. Staining characteristics were assessed for their statistical relationship to median survival time.

RESULTS

Overall median survival time was 189 days following the onset of clinical signs and 99 days following definitive diagnosis; 54% of cases had CD20⁺ staining. There was no statistically significant correlation between staining characteristics and median survival time from onset of signs (P = 0.54) or from diagnosis (P = 0.61).

CONCLUSIONS AND CLINICAL SIGNIFICANCE

Canine cutaneous epitheliotropic lymphoma has a higher instance of CD20 positivity than documented previously. This indicates that CD20 staining may be unsuitable to differentiate T-cell and B-cell cutaneous epitheliotropic lymphoma. This also may have therapeutic implications with the advent of canine CD20 monoclonal antibody therapies.

Multispectral Imaging Approach to the Diagnosis of a CD20+ Cutaneous T-cell Lymphoproliferative Disorder: A Case Report

Expression of the pan B-cell marker CD20 by T-cell lymphoproliferative disorders is exceedingly rare. We present a 52-year-old man with a unilesional cutaneous CD20 T-cell lymphoproliferative disorder. Multispectral imaging analysis of CD3-CD20 double-stained lesional tissue sections allowed (1) the visualization of double-positive T lymphocytes in situ with sensitivity superior to that of conventional immunohistochemistry and (2) the quantitative assessment of marker coexpression. Here, 23% of CD3 signals in the patient's lesion were also CD20, whereas 38% of CD20 signals were also CD3. In contrast, both parameters were below 1% in the tonsil control. Overall, the percentage of double-positive cells in lesional skin was 35%, although only 0.4% of such cells were detected in the tonsil. This is the first demonstration of aberrant CD20 expression by skin-infiltrating T cells using multispectral imaging.

CD3 and CD20 Coexpression in a Case of Canine Cutaneous Epitheliotropic T-Cell Lymphoma (Mycosis Fungoides)

A 14-year-old female spayed Dachshund was presented with generalized scaling, erythema, pruritus, poor quality of hair coat, and progressive weight loss. Cutaneous epitheliotropic T-cell lymphoma (CETCL) was suspected. Skin biopsies were suggestive of CETCL. However, immunohistochemistry revealed the presence of numerous CD20+ and CD3+ cells. Clonality assay demonstrated a clonal T-cell receptor gamma rearrangement and a polyclonal IgH gene rearrangement. Double-label immunofluorescence confirmed coexpression of CD3 and CD20 by neoplastic cells. By double immunohistochemistry, neoplastic cells were CD3+ and PAX5–. The results are compatible with a CD3+, CD20+ CETCL. Coexpression of CD20 and CD3 has been recognized in peripheral T-cell lymphomas. Although documented in human CETCL, it has not been reported in canine CETCL. The pathogenetic basis of CD20 expression in mycosis fungoides is explored.

CD8-positive peripheral T-cell lymphoma with aberrant expression of CD20 and concurrent in situ follicular lymphoma

A case of a 78-year-old woman with a CD8-positive peripheral T-cell lymphoma with aberrant expression of CD20 associated with follicular lymphoma in situ (FLIS) is reported. The neoplasm presented initially as cutaneous macules, papules, plaques and nodules. A skin biopsy was performed and the diagnosis of peripheral T-cell lymphoma (PTCl) with aberrant expression of CD20 was made. The staging procedures included an excisional inguinal lymph node biopsy that showed findings similar to those of the previous diagnosis. In addition, FLIS was identified. The clinicopathologic features of PTCLs with aberrant CD20 expression involving the skin as well as this uncommon association are reviewed.