A third of melanomas originate from benign melanocytic nevi, representing a transition between distinct stages of melanocytic neoplasia. To gain insight into the transcriptional and microenvironmental changes accompanying this transition, we employed spatially resolved, transcriptome-wide analysis combined with imaging mass cytometry on nevus-associated melanomas. The transcriptional alterations were multifaceted, broadly spanning three principal processes: increased proliferation coupled to metabolic adaptation, enrichment of melanocytic lineage-associated programs, and remodeling of the microenvironment. Proliferative activity in melanoma was marked by increased CDK2 expression. Alterations in the nevus and melanoma transcriptomes were accompanied by microenvironmental changes, including shifts in cellular composition and altered gene expression in keratinocytes and fibroblasts. Within the nevus, CD163+ M2-like macrophages were present, with few other infiltrating or surrounding immune cells. In contrast, melanoma regions were surrounded by abundant immune cells, including M1-like macrophages expressing chemokine genes and T cells bearing markers of repeated activation. Simultaneously, melanomas exhibited features associated with an immunosuppressive microenvironment. This study presents a spatial atlas of the nevus-to-melanoma transition, advancing our understanding of the transcriptomic shifts and local immune environment that characterize melanoma initiation.

In recent years, dermatoscopy has emerged as a valuable adjunctive tool for the diagnosis of various cutaneous disorders. Initially developed for the evaluation of melanocytic lesions, this non-invasive technique has since demonstrated significant utility in the assessment of non-melanocytic hyperpigmented dermatoses. This review provides an up-to-date and practical overview of the dermatoscopic manifestations of common non-melanocytic hyperpigmented conditions, including melasma, nevus of Ota, freckles, lentigines, solar lentigines, seborrheic keratosis, porokeratosis, acquired dermal macular hyperpigmentation, lichen planus-like keratosis, pigmented actinic keratosis, pigmented Bowen's disease, basal cell carcinoma, and acanthosis nigricans. Many of these hyperpigmented disorders exhibit distinct and characteristic dermatoscopic features. Given the clinical diagnostic challenges posed by these conditions and their significant psychological impact on patients, dermatoscopy offers a complementary approach to enhance the accuracy of evaluation and differential diagnosis.

Skin cancer diagnosis, particularly the differentiation of melanoma from benign nevi, is a vital yet challenging task due to the visual similarity between lesions. Although deep learning models such as convolutional neural networks (CNNs) and vision transformers (ViTs) have demonstrated promising performance, their effectiveness often deteriorates when applied to data from heterogeneous clinical sources. While conventional domain adaptation methods address domain shift, they require access to source data during adaptation, which is often infeasible due to privacy regulations. Multi-source-free unsupervised domain adaptation (MSFDA) addresses this limitation by leveraging multiple labeled source domains to generalize to an unlabeled target domain without requiring access to source data, making it suitable for privacy-sensitive medical settings. However, existing MSFDA methods rely on full backbone fine-tuning, leading to catastrophic forgetting and overfitting on small clinical datasets, and address domain shift at the aggregation stage without establishing a shared domain-invariant feature space. Furthermore, their reliance on hard pseudo-labels or confidence-weighted aggregation introduces noisy supervision signals under domain shift. To address these limitations, we propose CAT-CKD, consisting of two components: (1) contrastive adapter training (CAT), which trains lightweight ConvPass adapters within a frozen ViT backbone using supervised contrastive learning (SCL) to establish a shared domain-invariant feature space before source-specific model training, and (2) consensus knowledge distillation (CKD), which aggregates logits from multiple source models into a consensus supervisory signal and adapts a student model on unlabeled target data using KL divergence. Experiments on five publicly available skin lesion datasets show that CAT-CKD achieves an average AUROC of 86.1%, outperforming existing MSFDA methods while requiring only 4.3M trainable parameters. The code for this paper is available at https://github.com/A-Abedi/CAT_CKD.

A 52-year-old man with multiple scalp nodules for more than 30 years and a right occipital mass that had been progressively enlarging for the past 2 years and rupturing and draining for more than 6 months was pathologically confirmed to be secondary malignant proliferating trichilemmal cyst (MPTC). 18F-FDG PET/CT showed active glucose metabolism in the scalp lesion and similar hypermetabolism in the dorsal and right iliac spine skin nodules. This case demonstrates the significant advantages of 18F-FDG PET/CT whole-body imaging in evaluating malignant proliferating trichilemmal cyst, a rare disease.

A 34-year-old man from Guinea-Bissau presented with a rapidly growing tumor on his right foot over 6 months, arising from a long-standing pigmented papule present for more than 20 years. Clinical examination revealed an exophytic black tumor with ipsilateral inguinal lymphadenopathy. Histopathological analysis showed an epithelioid and fusiform melanocytic proliferation in the dermis with abundant melanin. Immunohistochemical staining demonstrated diffuse positivity for Sox-10, Melan-A, HMB45, and PRAME. A diagnosis of blue nevus-like melanoma (BNM) was confirmed. BRAF V600 mutation testing on a cutaneous metastasis was negative. Staging imaging revealed widespread metastases involving lymph nodes, brain, lungs, liver, stomach, duodenum, colon, adrenal glands, pancreas, gallbladder, and bones. Despite 4 cycles of ipilimumab/nivolumab immunotherapy, the disease progressed, and the patient died 4 months after diagnosis. BNM is a rare melanoma variant, often arising from a pre-existing blue nevus, with aggressive potential and frequent lymph node metastasis. The molecular heterogeneity of BNM and the limited therapeutic options underscore the need for further research into targeted therapies and prognostic biomarkers for this rare melanoma subtype.

Phacomatosis pigmentovascularis (PPV) is a term encompassing a group of disorders characterized by the coexistence of segmental pigmented nevi of melanocytic origin and segmental capillary nevi. Several variants are characterized by a hallmark nevus cesius. Systematic reviews on the topic are lacking. An extensive review and critical reassessment of worldwide literature was carried out. A total of 435, 17, 19, and 17 cases of phacomatosis cesioflammea, phacomatosis cesiomarmorata, phacomatosis cesioflammeomarmorata, and phacomatosis melanocesioflammea, respectively, were identified. Specific clinical manifestations emerged for each variant. Postzygotic mosaic mutations affecting the GNAQ or GNA11 genes have been identified for all these entities. Four cases of nevus cesius associated with nevus anemicus (NA) were also retrieved. Phacomatosis cesioflammea is confirmed to be the most common PPV type by far. Its extracutaneous manifestations mostly consist of Sturge-Weber-Klippel-Trénaunay syndrome-like abnormalities, and ocular melanoma is a rare but relevant occurrence. The clinical associations of phacomatosis cesioflammeomarmorata mostly seem to result from the presence of cutis marmorata telangiectatica congenita. Phacomatosis cesioflammeomarmorata seems to resemble phacomatosis cesioflammea in several respects. A high frequency of NA and the Klippel-Trénaunay phenotype (or leg-length discrepancy) was observed in phacomatosis melanocesioflammea. The existence of "pseudodidymosis cesioanemica" is also corroborated.

Distinguishing benign proliferative nodules (PNs) from melanoma arising within congenital melanocytic nevi remains a major diagnostic challenge. Copy number alteration (CNA) analysis is widely used to support classification, but current criteria were developed using array comparative genomic hybridization (aCGH). The performance of alternative platforms such as shallow whole-genome sequencing (sWGS) and methylation sequencing is poorly defined in this context. The objective of this study is to compare CNA profiles obtained from aCGH, sWGS, and methylation sequencing in atypical nodules arising within congenital nevi, and to explore their clinical context based on available follow-up data. Sixteen samples from 14 patients were retrospectively analyzed using all three platforms. CNAs were cataloged, concordance across methods was quantified using the Jaccard index, and molecular classifications were compared. Clinical follow-up was reviewed to provide clinical context. aCGH detected 39 CNAs, sWGS 60, and methylation sequencing 66. Concordance was highest between sWGS and methylation (mean Jaccard 0.67), followed by aCGH versus sWGS (0.64) and aCGH versus methylation (0.49). Cases with high aneuploidy demonstrated strong cross-platform agreement, whereas low-burden lesions exhibited greater variability between methods. Divergent molecular classifications were observed in six cases. While all methods reliably detect broad chromosomal changes, sWGS and methylation sequencing identify many additional focal CNAs that may not align with CGH-based diagnostic criteria. These findings highlight the need for platform-adapted thresholds and validation in larger outcome-linked cohorts.