Comfere, Nneka I.

AbstractBackgroundCertain autoimmune bullous dermatoses are mediated by autoantibodies of the IgG4 subclass. We determined the diagnostic impact of adding IgG4 to our conventional direct immunofluorescence (DIF) panel.MethodsFor all cases submitted to our referral laboratory for DIF over 1 month (n = 630), we performed IgG4 testing and collected consecutive biopsy specimens showing definite or indeterminate linear or cell‐surface deposition of IgG, IgG4, and/or C3. On retrospective blinded review, we classified the pattern and whether the findings were definite, indeterminate, or negative. When present, substantial background staining was recorded.ResultsSeventy DIF specimens met the inclusion criteria. Of 22 (31.4%) specimens equivocal for linear or cell‐surface deposition, 9 (40.9%) had definitive IgG4 findings, either linear (3 of 14 equivocal linear cases; 21.4%) or cell‐surface (6 of 8 equivocal cell‐surface cases; 75.0%). Background deposition was substantial in 14 cases (20.0%) for IgG but in none for C3 or IgG4.ConclusionIgG4 allowed the classification of over 40% of DIF cases that were otherwise equivocal by IgG and C3. IgG4 staining showed lower levels of non‐specific background staining than IgG or C3. IgG4 appears to contribute most value in cases with cell‐surface deposition or with equivocal linear IgG deposition and negative C3 results.

AbstractBackgroundAppropriate use criteria (AUC) provide patient‐centered physician guidance in test selection. An initial set of AUC was reported by the American Society of Dermatopathology (ASDP) in 2018. AUC reflect evidence collected at single timepoints and may be affected by evolving evidence and experience. The objective of this study was to update and expand AUC for selected tests.MethodsRAND/UCLA (RAND Corporation [Santa Monica, CA]/University of California Los Angeles) methodology used includes the following: (a) literature review; (b) review of previously rated tests and previously employed clinical scenarios; (c) selection of previously rated tests for new ratings; (d) development of new clinical scenarios; (e) selection of additional tests; (f) three rating rounds with feedback and group discussion after rounds 1 and 2.ResultsFor 220 clinical scenarios comprising lymphoproliferative (light chain clonality), melanocytic (comparative genomic hybridization, fluorescence in situ hybridization, reverse transcription polymerase chain reaction, telomerase reverse transcriptase promoter), vascular disorders (MYC), and inflammatory dermatoses (periodic acid‐Schiff, Gömöri methenamine silver), consensus by panel raters was reached in 172 of 220 (78%) scenarios, with 103 of 148 (70%) rated “usually appropriate” or “rarely appropriate” and 45 of 148 (30%), “appropriateness uncertain.” Limitations: The study design only measures appropriateness. Cost, availability, test comparison, and additional clinical considerations are not measured. The possibility that the findings of this study may be influenced by the inherent biases of the dermatopathologists involved in the study cannot be excluded.ConclusionsAUC are reported for selected diagnostic tests in clinical scenarios that occur in dermatopathology practice. Adhering to AUC may reduce inappropriate test utilization and improve healthcare delivery.

Background: Observations highlighting the “unmasking” of cutaneous T-cell lymphoma after treatment with dupilumab for atopic dermatitis (AD) have been recently reported. However, there remains a paucity of literature describing the evolution of clinical and histopathological features that characterizes this phenomenon. Objective: To define the clinical and histopathologic evolution of atypical lymphoid infiltrates after the administration of dupilumab for AD. Methods: A cross-sectional study of clinical and histopathologic features in 7 consecutive patients with a diagnosis of “atypical lymphoid infiltrate” or mycosis fungoides (MF) on dupilumab for AD was performed. Results: Seven patients with atypical lymphoid infiltrates or MF in evolution after dupilumab therapy (age range 27–74 years) were reviewed. Average duration of AD before MF diagnosis was 5.7 years, and the average duration on dupilumab treatment was 9.8 months. Notable histopathologic features across predupilumab and postdupilumab biopsies included progressive increase in the densities of the atypical lymphoid infiltrates (7/7), presence of atypical epidermotropic lymphocytes (6/7), and papillary dermal fibrosis (6/7). Limitations: Small retrospective cohort study. Conclusion: These cases highlight the transformation of lymphoid infiltrates after dupilumab treatment for AD and emphasize the importance of clinical and histopathologic evaluation before and during treatment with dupilumab for treatment-refractory presumed AD.

Background: Subcutaneous lymphomas are a heterogeneous group of diseases with variable clinical behavior that ranges from a lymphoproliferative disorder to an aggressive cytotoxic lymphoma. Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is an uncommon, often indolent cutaneous lymphoma that localizes to the subcutaneous adipose tissue. These tumors exhibit an alpha/beta phenotype (abSPTCL). Primary cutaneous gamma-delta T-cell lymphoma (PCgdTCL) is a rare, highly aggressive lymphoma that frequently involves the subcutaneous adipose tissue. The goal of this study is to identify key inflammatory and oncogenic pathways in SPTCL and PCgdTCL to determine which mutational or expression patterns differentiate abSPTCL and PCgdTCL. A comprehensive catalog of cancer gene expression profiles generated via RNA sequencing on patient samples is essential to understand tumorigenesis and to develop effective therapies. Methods: We performed transcriptomic profiling analysis using RNA sequencing in lesional skin biopsies from patients of abSPTCL (n=10), PCgdTCL (n=9), and controls (n=5). Differential analyses were performed on the entire transcriptomic profiles among the 3 groups. Results: Although the transcriptomic profiles of abSPTCL and PCgdTCL samples had similarities, there were notable differences between these groups that may elucidate unique pathways that propagate each disease. In contrast to abSPTCL, PCgdTCL samples demonstrated upregulation of cell motility and proliferation, and downregulation of pathways involving apoptosis and tumor necrosis factor production. The most significantly upregulated gene pathways in both abSPTCL and PCgdTCL samples were those involving immune and inflammatory response, viral defense, type I interferon signaling, interferon-gamma-mediated signaling, and positive regulation of T cell proliferation. The most significantly downregulated gene pathways in the two groups were those involving cell adhesion, rRNA processing and translation, and extracellular matrix organization. The top 5 upregulated immune response and downregulated cell adhesion hub genes for abSPTCL highlighted by gene interaction network analysis included: TNF, CTLA4, CD86, IL10, CCR5 & ITGB5, ITGA8, VWF, APP, CDH5, respectively. Conclusion: Our transcriptomic profiling pinpoints disease-related enrichment pathways and gene functions in abSPTCL and PCgdTCL patients, which may shed light on molecular mechanisms that drive disease activity. Hub genes in abSPTCL represent potential drug targets for further development of novel therapies. Disclosures Mangold: Kirin:Membership on an entity's Board of Directors or advisory committees;Elorac:Research Funding;Sun Pharma:Research Funding;MiRagen:Research Funding;Solagenix:Research Funding.

Background: Folliculotropic mycosis fungoides (FMF) is a variant of cutaneous T-cell lymphoma that has clinical overlap with a variety of inflammatory follicular unit disorders. However, we describe distinctive presentations of FMF with acneiform features that can be diagnostically challenging, leading to diagnostic delay. Objective: To highlight the importance of histopathologic and immunohistochemical evaluation for diagnostic confirmation of presumed inflammatory follicular unit–based disorders that are unusual in presentation or unresponsive to standard therapies. Methods: A cross-sectional retrospective study of 5 consecutive patients with a histopathologic diagnosis of FMF was conducted. The clinical, histopathologic, immunophenotypic, and molecular genetic features of cases are presented. Results: We describe 5 patients with clinical and histopathologic presentations of FMF masquerading as hidradenitis suppurativa, furunculosis, or acne vulgaris (age range 34–66 years, 4:1 female to male). Clinical morphologies included open and closed comedones, inflammatory pustules, papules and nodules, follicular papules with keratotic plugging, cysts, and scarring involving the face, trunk, and intertriginous areas. All patients failed to respond to standard therapies, including topical and oral antibiotics, topical and oral retinoids, or topical corticosteroids, before receiving the diagnosis of FMF. Lesional skin biopsies showed a perifollicular CD4-positive T-lymphocytic infiltrate with pilotropism, intrafollicular mucin deposition, foreign-body granulomatous inflammation, acute inflammation, and follicular epithelial necrosis. None had concurrent systemic mycosis fungoides. Limitations: Small retrospective cohort study. Conclusion: We present these cases to expand the clinical and histopathologic spectrum of FMF that may strikingly resemble acneiform disorders and to highlight the importance of diagnostic reconsideration with histopathologic evaluation.

Abstract 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.