Pemetrexed-Induced Pseudocellulitis: A Diagnostic Conundrum.

Pemetrexed, an anti-folate, antineoplastic agent, effectively treats various malignancies such as non-small cell lung cancer (NSCLC) and mesothelioma. Here, we report two cases of recurrent pemetrexed-induced lower extremity erythema and edema, one in a 60-year-old male and the other in a 47-year-old male, who were both treated for recurrent cellulitis on multiple occasions before finally being diagnosed with pemetrexed-induced pseudocellulitis (PIP), a rarely reported adverse effect. This is an important diagnostic pitfall for clinicians to be aware of, as early recognition may minimize patient morbidity and prevent unnecessary hospitalization and antibiotic use for presumed cellulitis.

The diagnostic conundrum of acute cutaneous graft-versus-host disease: biomarkers remain elusive.

Hematopoietic stem cell transplantation is increasing in frequency with graft-versus-host disease affecting many recipients. When the skin is involved, biopsy is routinely performed but often does not aid in definitive diagnosis. Here, we examine a cohort of 32 patients for potential biomarkers that can aid in the diagnosis of graft-versus-host disease. Neither blood short tandem repeat testing or neutrophil-lymphocyte ratios were predictive of rash etiology in hematopoietic stem cell transplant patients. However, skin short tandem repeat testing showed promise as a predictor in a small minority of cases in this cohort.

Distinguishing Keratoacanthoma from Well-Differentiated Cutaneous Squamous Cell Carcinoma Using Single-Cell Spatial Pathology.

Keratoacanthoma (KA) is a common keratinocyte neoplasm that is regularly classified as a type of cutaneous squamous cell carcinoma (cSCC) despite demonstrating benign behavior. Differentiating KA from well-differentiated cSCC is difficult in many cases due to the substantial overlap of clinical and histological features. Currently, no reliable discriminating markers have been defined, and consequently, KAs are often treated similarly to cSCC, creating unnecessary surgical morbidity and healthcare costs. In this study, we used RNA sequencing to identify key differences in transcriptomes between KA and cSCC, which suggested divergent keratinocyte populations between each tumor. Imaging mass cytometry was then used to identify single-cell tissue characteristics, including cellular phenotype, frequency, topography, functional status, and interactions between KA and well-differentiated cSCC. We found that cSCC had significantly increased proportions of Ki67+ keratinocytes among tumor keratinocytes, which were dispersed significantly throughout non-basal keratinocyte communities. In cSCC, regulatory T-cells were more prevalent and held greater suppressive capacity. Furthermore, cSCC regulatory T-cells, tumor-associated macrophages, and fibroblasts had significant associations with Ki67+ keratinocytes as opposed to avoidances with KA, indicating a more immunosuppressive environment. Our data suggest that multicellular spatial features can serve as a foundation to enhance the histological discrimination of ambiguous KA and cSCC lesions.

Real world validation of an adjunctive gene expression-profiling assay for melanoma diagnosis and correlation with clinical outcomes at an academic center.

A commercially available diagnostic gene expression profiling (GEP) assay (MyPath™) reportedly has high sensitivity and specificity in distinguishing nevi from melanoma based on manufacturer-conducted studies. However, data regarding the performance of this GEP assay in routine clinical practice are lacking. The purpose of this study was to better assess the real-world performance of GEP in a large academic practice. Retrospective review of GEP scores were compared with final histomorphologic interpretation on a wide spectrum of melanocytic lesions demonstrating some degree of atypia. In a sample of 369 lesions, the sensitivity (76.1%) and specificity (83.9%) of the GEP test as compared with final dermatopathologist-rendered diagnosis in our dataset was appreciably lower than that reported in the prior manufacturer-conducted validation studies. Limitations of this study were that it was a single-center study, its retrospective nature, nonblinded nature of GEP test result, concordance of only two pathologists, and limited follow-up time.The sensitivity and specificity of a commercially available GEP diagnostic assay for melanoma may be lower in routine clinical practice, where melanocytic lesions typically exhibit some degree of histomorphologic atypia. Reported cost effectiveness of GEP testing is questionable if all ambiguous lesions that undergo such testing are re-excised in clinical practice.

Single-Fraction Radiation Therapy for Localized Cutaneous T-Cell Lymphoma.

PURPOSE: Mycosis fungoides is the most common type of cutaneous T-cell lymphoma (CTCL). Single-fraction radiation therapy has been used as a skin-targeted therapy to treat localized CTCL lesions. The objective of this study was to investigate the treatment outcomes associated with single-fraction radiation therapy for CTCL. METHODS AND MATERIALS: We retrospectively studied the outcomes among patients with CTCL treated with single-fraction radiation therapy at our institution between October 2013 and August 2022. Clinical response (complete response [CR], partial response [PR], or no response [NR]) and retreatment response were evaluated. RESULTS: A total of 242 lesions from 46 patients were analyzed, for an average of 5.3 lesions treated per patient. The majority of lesions presented with a plaque morphology (n = 145, 60.0%). All lesions were treated to a dose of 8 Gy in 1 fraction. Median follow-up was 24.6 months (range, 1-88 months). Of the 242 lesions, 36 (14.8%) had an initial PR or NR; all were retreated with the same regimen to the same site at a median interval of 8 weeks. Eighteen of the retreated lesions (50.0%) went on to have a CR. Thus, the overall CR rate for CTCL lesions was 92.6%. No recurrences were noted in the treated areas after achieving CR. CONCLUSIONS: Single-fraction radiation therapy to a dose of 8 Gy in 1 fraction to localized areas provided a high rate of complete and durable responses in the affected sites.

Dysregulated CD38 expression in blood and skin immune cells of patients with hidradenitis suppurativa.

Hidradenitis suppurativa (HS) is a multifactorial, inflammatory skin disease. Increased systemic inflammatory comorbidities and serum cytokines highlight systemic inflammation as a feature of HS. However, the specific immune cell subsets contributing to systemic and cutaneous inflammation have not been resolved. Here, we generated whole-blood immunomes by mass cytometry. We performed a meta-analysis of RNA-seq data, immunohistochemistry, and imaging mass cytometry to characterize the immunological landscape of skin lesions and perilesions from patients with HS. Blood from patients with HS exhibited lower frequencies of natural killer cells, dendritic cells, and classical (CD14+CD16-) and nonclassical (CD14-CD16+) monocytes, as well as higher frequencies of Th17 cells and intermediate (CD14+CD16+) monocytes than blood from healthy controls. Classical and intermediate monocytes from patients with HS had increased expression of skin-homing chemokine receptors. Furthermore, we identified a CD38+ intermediate monocyte subpopulation that was more abundant in the immunome of blood from patients with HS. Meta-analysis of RNA-seq data found higher CD38 expression in lesional HS skin than in perilesional skin, and markers of classical monocyte infiltration. Imaging mass cytometry showed that CD38+ classical monocytes and CD38+ monocyte-derived macrophages were more abundant in lesional HS skin. Overall, we report targeting CD38 may be worth pursuing in clinical trials.

Dysregulated CD38 expression in blood and skin immune cells of patients with hidradenitis suppurativa.

Background: Hidradenitis suppurativa (HS) is a multifactorial, inflammatory skin disease. Increased systemic inflammatory comorbidities and serum cytokines highlight systemic inflammation as a feature of HS. However, the specific immune cell subsets contributing to systemic and cutaneous inflammation have not been resolved. Objective: Identify features of peripheral and cutaneous immune dysregulation. Methods: Here, we generated whole-blood immunomes by mass cytometry. We performed a meta-analysis of RNA-seq data, immunohistochemistry, and imaging mass cytometry to characterize the immunological landscape of skin lesions and perilesions from patients with HS. Results: Blood from patients with HS exhibited lower frequencies of natural killer cells, dendritic cells, and classical (CD14+CD16-) and nonclassical (CD14-CD16+) monocytes, as well as higher frequencies of Th17 cells and intermediate (CD14+CD16+) monocytes than blood from healthy controls. Classical and intermediate monocytes from patients with HS had increased expression of skin-homing chemokine receptors. Furthermore, we identified a CD38+ intermediate monocyte subpopulation that was more abundant in the immunome of blood from patients with HS. Meta-analysis of RNA-seq data found higher CD38 expression in lesional HS skin than in perilesional skin, and markers of classical monocyte infiltration. Imaging mass cytometry showed that CD38+ classical monocytes and CD38+ monocyte-derived macrophages were more abundant in lesional HS skin. Conclusion: Overall, we report targeting CD38 may be worth pursuing in clinical trials. Key Messages: 3.Monocyte subsets express markers of activation in circulation and HS lesionsTargeting CD38 may be a viable strategy for treating systemic and cutaneous inflammation in patients with HS. Capsule Summary: 4.Dysregulated immune cells in patients with HS express CD38 and may be targeting by anti-CD38 immunotherapy.

Imaging technologies for presurgical margin assessment of basal cell carcinoma.

Basal cell carcinoma is the most common cancer worldwide, necessitating the development of techniques to decrease treatment costs through efficiency and efficacy. Mohs micrographic surgery, a specialized surgical technique involving staged resection of the tumor with complete histologic evaluation of the peripheral margins, is highly utilized. Reducing stages by even 5% to 10% would result in significant improvement in care and economic benefits. Noninvasive imaging could aid in both establishing the diagnosis of suspicious skin lesions and streamlining the surgical management of skin cancers by improving presurgical estimates of tumor sizes. Herein, we review the current state of imaging techniques in dermatology and their applications for diagnosis and tumor margin assessment of basal cell carcinoma prior to Mohs micrographic surgery.

Surface translocation of ACE2 and TMPRSS2 upon TLR4/7/8 activation is required for SARS-CoV-2 infection in circulating monocytes.

Infection of human peripheral blood cells by SARS-CoV-2 has been debated because immune cells lack mRNA expression of both angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease type 2 (TMPRSS2). Herein we demonstrate that resting primary monocytes harbor abundant cytoplasmic ACE2 and TMPRSS2 protein and that circulating exosomes contain significant ACE2 protein. Upon ex vivo TLR4/7/8 stimulation, cytoplasmic ACE2 was quickly translocated to the monocyte cell surface independently of ACE2 transcription, while TMPRSS2 surface translocation occurred in conjunction with elevated mRNA expression. The rapid translocation of ACE2 to the monocyte cell surface was blocked by the endosomal trafficking inhibitor endosidin 2, suggesting that endosomal ACE2 could be derived from circulating ACE2-containing exosomes. TLR-stimulated monocytes concurrently expressing ACE2 and TMPRSS2 on the cell surface were efficiently infected by SARS-CoV-2, which was significantly mitigated by remdesivir, TMPRSS2 inhibitor camostat, and anti-ACE2 antibody. Mass cytometry showed that ACE2 surface translocation in peripheral myeloid cells from patients with severe COVID-19 correlated with its hyperactivation and PD-L1 expression. Collectively, TLR4/7/8-induced ACE2 translocation with TMPRSS2 expression makes circulating monocytes permissive to SARS-CoV-2 infection.

The Roles of Skin Langerhans Cells in Immune Tolerance and Cancer Immunity.

Langerhans cells (LC) are a unique population of tissue-resident macrophages with dendritic cell (DC) functionality that form a network of cells across the epidermis of the skin. Their location at the skin barrier suggests an important role for LC as immune sentinels at the skin surface. The classification of LC as DC over the past few decades has driven the scientific community to extensively study how LC function as DC-like cells that prime T cell immunity. However, LC are a unique type of tissue-resident macrophages, and recent evidence also supports an immunoregulatory role of LC at steady state and during specific inflammatory conditions, highlighting the impact of cutaneous environment in shaping LC functionality. In this mini review, we discuss the recent literature on the immune tolerance function of LC in homeostasis and disease conditions, including malignant transformation and progression; as well as LC functional plasticity for adaption to microenvironmental cues and the potential connection between LC population heterogeneity and functional diversity. Future investigation into the molecular mechanisms that LC use to integrate different microenvironment cues and adapt immunological responses for controlling LC functional plasticity is needed for future breakthroughs in tumor immunology, vaccine development, and treatments for inflammatory skin diseases.

ETS-related Gene (ERG) is Differentially Expressed in Dermatofibroma (Fibrous Histiocytoma) as Compared With Dermatofibrosarcoma Protuberans and Hypertrophic Scars: A Pilot Immunohistochemical Study.

Immunohistochemical staining can be of great utility in differentiating various cutaneous spindle cell neoplasms, particularly when the histomorphologic appearance of the lesions is inconclusive. Nuclear staining for ETS-related gene (ERG), a highly sensitive endothelial cell marker, has seldom been studied in the context of cutaneous spindle cell neoplasms. Little is known about its specificity for vascular differentiation. In this pilot study, immunohistochemical analysis for ERG was performed on 15 dermatofibromas (DF), 10 keloids, and 9 dermatofibrosarcoma protuberans (DFSP) tumors. Consistent nuclear expression of ERG was found in DF [100% (15/15) of the lesions demonstrated >50% labeling of tumor cells with moderate to strong intensity]. However, ERG expression was largely absent in DFSP [89% (8/9) of the lesions demonstrating <50% labeling staining, generally of mild intensity] and hypertrophic scars-keloids [80% (8/10) without expression]. On the basis of the results of this pilot study, immunohistochemical staining for ERG may prove useful in helping to differentiate DF from DFSP and hypertrophic scars in the context of partial biopsy sampling. If replicated in a larger number of samples, this finding could mitigate the use of costly sequencing panels and potentially avoid unnecessary reexcisions in certain contexts.