The Histopathological Spectrum of Pseudolymphomatous Infiltrates in Cutaneous Lupus Erythematosus

Kappa and lambda immunohistochemistry and in situ hybridization in the evaluation of atypical cutaneous lymphoid infiltrates

BACKGROUND

Atypical cutaneous lymphoid infiltrates are challenging lesions in dermatopathology. We present a summary of the literature regarding kappa and lambda immunohistochemistry (IHC) and in situ hybridization (ISH) in the evaluation of atypical cutaneous or mucosal lymphoid infiltrates.

METHODS

Relevant articles from 1967 to 2018 in the English language were identified and summarized. In the absence of larger studies, case series of n ≥ 3 were included.

RESULTS

Sixty-three articles assessing kappa and lambda IHC and/or ISH were identified. Most focused on marginal zone lymphomas. Other lymphomas included follicle center lymphoma, diffuse large B-cell lymphoma, chronic lymphocytic leukemia/small lymphocytic lymphoma, mantle cell lymphoma, lymphoplasmacytic lymphoma, plasmablastic lymphoma, multiple myeloma, monoclonal gammopathy of undetermined significance, and polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, skin changes (POEMS). Non-neoplastic lesions included reactive lymphoid hyperplasia, cutaneous plasmacytosis, connective tissue disease, IgG4-related disease, acrodermatitis chronic atrophicans, Zoon balanitis, dermatitides, and infiltrates around epithelial dysplasias/neoplasias.

CONCLUSION

Kappa and lambda IHC and ISH are useful tools in the evaluation of cutaneous B-cell lymphomas and plasma cell neoplasms. The literature supports that the detection of light-chain restriction by IHC and ISH is one of the most useful findings in the differential diagnosis of reactive lymphoid hyperplasia vs B-cell lymphoma with plasmacytic differentiation.

Lupus Erythematosus Tumidus with Pseudolymphomatous Infiltrates: A Case Report

A 39-year-old Japanese woman presented with a pruritic infiltrated erythematous plaque on the right cheek. Histopathologic analysis of the erythema showed dermal edema, separation of collagen bundles, and nodular perivascular and periadnexal infiltration of lymphocytes in the whole dermis, without epidermal changes. Alcian blue staining intensity was elevated between the collagen bundles, indicating dermal mucinosis. The nodular infiltrates consisted of CD3+ T cell clusters and CD20+ B cell clusters (ratio, approximately 3:1) and included numerous CD123+ cells, indicative of plasmacytoid dendritic cells. Blood analysis revealed serum antinuclear antibody at a titer of 1:160 (homogeneous, speckled pattern). Lupus erythematosus tumidus with pseudolymphomatous infiltrates was diagnosed. Hydroxychloroquine treatment partially improved symptoms; however, the addition of prednisolone was required for complete resolution. Lupus erythematosus tumidus is sometimes accompanied by pseudolymphomatous infiltrates. Dermal mucinosis and the presence of numerous plasmacytoid dendritic cells are useful in differentiating lupus erythematosus tumidus from pseudolymphoma.

Lupus erythematosus tumidus: clinical perspectives

Lupus erythematosus tumidus (LET) is an uncommon and photosensitive inflammatory skin disorder which is characterised by erythematous urticarial plaques. In the last 20 years, extensive research on clinical and histological aspects of the disease have led to a better characterization of this nosological entity and to differentiate it from other similar or related diseases. Today, LET is considered as a separate subtype of cutaneous lupus erythematosus (CLE) with a benign, intermittent clinical course (intermittent CLE, ICLE) and only rarely associated with systemic lupus erythematosus (SLE).

Plasmacytoid dendritic cells in granulomatous variant of mycosis fungoides

INTRODUCTION

Granulomatous mycosis fungoides (MF) is a rare variant in which granulomas are associated with other typical signs of MF. Its prognosis is worse than that of classical MF. Plasmacytoid dendritic cells (PDCs) are a subset of interferon-producing dendritic cells that link the innate and the adaptative immune responses. They have also been related to tolerance to certain tumors such as melanoma.

MATERIALS AND METHODS

In this article, we examined for the presence of CD123+ PDC in six cases of granulomatous MF from our archives.

RESULTS

We found clusters of 10 or more positive cells in three of six cases of granulomatous MF (two women and a man, in their sixth and seventh decade). Although in two of these three cases the granulomatous response was extensive, in the other, it only represented 10% of the infiltrate of the biopsy. In all three cases, the granulomas were epithelioid, sarcoidal type.

CONCLUSIONS

CD123+ PDC can be identified in granulomatous MF. The pathogenic and prognostic role of this finding requires further clarification.

Loss of 5-Hydroxymethylcytosine Is an Epigenetic Biomarker in Cutaneous T-Cell Lymphoma

DNA hydroxymethylation at the 5 position of cytosine (5-hmC) is a product of the TET family of DNA hydroxylases. Accumulating evidence shows that loss of 5-hmC is critical for various biological and pathological processes. However, its level in cutaneous T-cell lymphoma (CTCL) remains largely unknown. Here, we report that the loss of 5-hmC is an epigenetic hallmark of CTCL, with diagnostic and prognostic implications. Immunohistochemistry staining on 90 mycosis fungoides (MF) samples showed a significant decrease of 5-hmC staining in CD4⁺ T cells in patch and tumor stages, especially in MF with large cell transformation, compared with benign inflammatory dermatoses. The 5-hmC staining level decreased with disease progression and showed remarkable loss in the large cells of large cell transformed MF samples, regardless of the CD30 positivity. Furthermore, 5-hmC decrease was correlated to poor overall survival in our patient cohort. Pharmacological augments of global 5-hmC with l-ascorbic acid in CTCL cell lines led to remarkable 5-hmC accumulation and promoted apoptosis in CTCL cell lines, as well as in patient-derived CTCL cells. In conclusion, 5-hmC is an epigenetic mark of predictive value in MF prognosis. Restoration of 5-hmC levels in MF may serve as a therapeutic regimen in CTCL.