Acantholytic dyskeratosis and epidermolytic hyperkeratosis are distinct histopathologic patterns reflecting abnormalities in keratinocyte differentiation. Although typically considered separate histopathologic reaction patterns, their coexistence within a single lesion is uncommon and remains poorly characterized. We report the case of a 51-year-old woman with a lumbar skin lesion excised for suspected intradermal nevus or basal cell carcinoma. Histopathologic examination revealed a combination of Acantholytic dyskeratosis and epidermolytic hyperkeratosis features without evidence of malignancy. This association, previously described in the literature, suggests that both patterns may represent overlapping responses within a shared spectrum of epidermal alterations, potentially triggered by external factors or occurring as incidental findings. Recognition of this coexistence is important for accurate histopathologic classification of keratotic lesions and to avoid overinterpretation of incidental epidermolytic change. In most cases, it likely represents a secondary phenomenon without direct clinical significance, although further studies are needed to clarify its pathogenic basis.

Neurocutaneous melanosis (NCM) and Dandy-Walker malformation (DWM) are both uncommon congenital condition, involving the central nervous system (CNS). Combined NCM with DWM have been reported in a few studies. Potential consequences, including hydrocephalus and CNS malignancies make these illnesses extremely challenging to diagnose and treat. Occurrences of NCM and DWM together, can result in progressive neurological consequences and patients with this condition seems to have really poor prognosis. This case report describes a 5-day-old girl who was born with several large pigmented cutaneous nevi all over her body. She was born at term to non-consanguineous parents who had no family history of similar conditions. Imaging studies, such as brain CT scan, showed cystic dilatation of the fourth ventricle, hypoplasia of the cerebellar vermis, enlargement of the posterior fossa, and possibly secondary hydrocephalus-all of which are indicative of DWM. A biopsy of the nevi confirmed NCM. The patient had no neurological symptoms or systemic complications at the time of presentation. The combination of NCM and DWM is extremely rare, with fewer than 40 reported cases so far. While the exact connection between these two conditions is not fully understood, their coexistence of these conditions might be linked to their shared embryonic origin. Both melanocytes and parts of the CNS come from the neural crest during early development. Since these conditions can have serious neurological and systemic effects, managing them requires multidisciplinary care because of potential consequences of these disorders.

Conjunctival lesions in children are nearly always benign. The most common are conjunctival nevi. The rare malignant conjunctival tumors in children are usually larger and appear at an older age. Children with xeroderma pigmentosum are a unique group in whom malignant conjunctival tumors can occur at an early age. In this review, we describe common and rare benign and malignant conjunctival lesions in children, grouped by tissue of origin.

Giant congenital melanocytic nevi of the scalp are rare congenital melanocytic lesions associated with cranial bone defects. Cranioplasty can be technically challenging, particularly in the absence of normal subcutaneous tissues and dissection planes. However, few surgical reports have focused on these technical difficulties. A girl (age: 6 years and 5 months) with a congenital pigmented scalp lesion, slightly to the right of the midline, underwent postnatal cranial computed tomography scanning that revealed a large cranial bone defect extending from the frontal to parietal bones. Histopathological examination of a biopsy specimen revealed a blue nevus. Considering the patient's normal neurodevelopment and the non-progression of the bone defect during follow-up, elective cranioplasty was planned before school admission. Cranioplasty using a custom-made artificial bone was performed in collaboration with plastic surgeons. Intraoperative findings revealed the absence of normal subcutaneous tissue and the subgaleal dissection plane. The dermis directly adhered to the cranial bone and dura mater, and partially to arachnoid-like tissue. Sharp dissection under careful tension was undertaken with minimal dural injury to preserve scalp viability. Postoperatively, subcutaneous fluid collection and minor scalp necrosis occurred and were successfully managed with local wound care and continuous swimming-cap compression. Congenital melanocytic scalp lesions may be associated with cranial bone defects and loss of normal tissue planes, with severe adhesions between the scalp and intracranial structures. Surgeons should consider these anatomical abnormalities when planning cranioplasty and customize surgical strategies to preserve scalp viability while minimizing intracranial complications.

Spitzoid tumors comprise a heterogeneous spectrum of melanocytic neoplasms, ranging from benign Spitz nevi to malignant Spitzoid melanoma, with atypical Spitz tumor (AST) representing an intermediate entity of uncertain biological potential. AST is a rare melanocytic lesion that may clinically mimic non-melanocytic tumors, particularly dermatofibroma, making accurate diagnosis challenging. It predominantly affects children and young adults and has a predilection for the lower extremities. We describe two cases of young female patients presenting with clinically similar erythematous-pigmented plaques on the thigh. Despite comparable clinical appearances, dermoscopic evaluation revealed distinct patterns that led to different diagnoses: a spitzoid melanocytic proliferation (confirmed as AST on histology) and a dermatofibroma, with markedly divergent biological behaviors and prognostic implications. In spitzoid lesions, the presence of dotted vessels, shiny white streaks, inverse pigment network, and/or brown globules should raise suspicion of a melanocytic spitzoid proliferation. In contrast, the dermatofibroma exhibited a peripheral pigmented network, a central scar-like white area, and brown ringed globules, consistent with the typical dermoscopic pattern of this benign fibrohistiocytic tumor. These observations underscore the value of dermoscopy as a diagnostic triage tool in the assessment of spitzoid lesions. However, definitive diagnosis still relies on histopathological evaluation.

Eruptive nevi and lentigines have been reported to occur in the setting of immunosuppression, which may be medication-induced. The associated histopathologic findings have not been well described in the literature. Herein, we report the case of a woman in her 60s who had been receiving chemotherapy treatment with capecitabine, a prodrug of 5-fluorouracil, for advanced pancreatic cancer. She developed multiple small, dark macules on the dorsal and plantar surfaces of both feet. An initial biopsy of one lesion showed a crowded lentiginous proliferation of predominantly single melanocytes, with poor nest formation and some pagetoid scatter. Subsequent biopsies revealed lentigines with melanocytic hyperplasia, which showed less cellularity than the initial biopsy. This case provides histopathologic correlation for eruptive acral melanocytic lesions that result from capecitabine therapy.

Somatic overgrowth and vascular anomalies are often present at birth but may only be clinically recognized later in life. Affected tissues commonly include veins and arteries, skin, adipose tissue, bone, and brain, resulting in a broad phenotypic spectrum encompassing vascular malformations, lipomatous and melanocytic nevus syndromes, skeletal abnormalities, and brain malformations. These conditions are typically caused by postzygotic variants present in a subset of cells due to mosaicism. The developmental timing and cell lineages involved determine the extent and distribution of affected tissues. While germline variants and their clinical consequences are well characterized, the impact of somatic mosaic variants remains less well understood. Because these variants are often absent or present at very low levels in blood, sensitive assays and analysis of affected tissues are required for detection. Advances in high-depth next-generation sequencing have enabled reliable identification of low-level mosaic variants and are central to the genetic diagnosis of these disorders. Numerous causative genes have been described, most notably activating variants in the PI3K-MTOR and RAS-MAPK pathways. Genetic testing provides diagnostic confirmation, informs prognosis and recurrence risk, and in some cases enables targeted therapy, such as alpelisib for PIK3CA-related overgrowth spectrum. However, testing strategies vary across laboratories in gene panel content, sequencing depth, and tissue requirements, leading to inconsistent diagnostic approaches. This review summarizes known causative genes, current testing methodologies, variant interpretation and reporting practices, major genomic alteration classes and recurrent hotspot variants, and highlights key knowledge gaps from clinical and laboratory perspectives.

Nevus spilus (NS) is a melanocytic lesion characterized by multiple darker macules or papules within a lighter-brown background patch. It is generally considered benign, but rarely melanoma may arise within NS. This association is controversial and poorly quantified. We systematically reviewed the literature on melanoma arising in NS and describe two additional reports. Clinical, histopathologic, molecular, and outcome data were extracted from all eligible cases. The aim of our study was to analyze the clinicopathological patterns, risk factors, and management implications. A total of 39 cases met inclusion criteria, suggesting that melanoma arising in NS is rare but not anecdotal. Most cases occurred in large, congenital, zosteriform lesions; the predominant location was the trunk, followed by the lower and upper limbs; the most common histotype was superficial spreading melanoma (SSM). Favorable outcomes were associated with early detection and thinner lesions, whereas thicker or nodular melanomas and delayed diagnosis correlated with poorer prognosis. Molecular data were limited but suggested possible heterogeneity, with infrequent BRAF/NRAS mutations. The risk of melanoma arising in NS appears to be subtype-dependent rather than uniform. Routine prophylactic excision of NS lesions is not supported by current evidence. A structured clinical and dermoscopic follow-up - particularly for larger, congenital, and segmental lesions - may represent a balanced management strategy, facilitating earlier identification of malignant transformation and ultimately improving patient outcomes. Further molecular profiling studies are needed to clarify pathogenetic mechanisms and refine risk stratification.

Optic disc melanocytoma (ODM) is a benign pigmented tumor historically regarded as stationary. ODM can produce visual dysfunction and rarely undergoes malignant transformation. We synthesize evidence on predicting visual field defects and recognizing malignant transformation. Optical coherence tomography angiography (OCTA) studies demonstrate that visual field defects correlate more strongly with absent intratumoral blood vessel networks than with tumor size. A validated threshold of capillary density loss > 0.75% per year identifies patients at increased risk of visual field progression. OCTA measurements demonstrate high intra-device reproducibility (intraclass correlation coefficients >0.8) but poor inter-device reliability, requiring strict standardization. Regarding malignant transformation, a synthesis of case series indicates a rate of approximately 1.7%, with transformation potentially occurring decades after diagnosis. OCTA detects malignant transformation through identification of intrinsic tumor vasculature. In choroidal studies, intralesional vessel diameter ≥ 76.3μm has demonstrated 100% sensitivity and specificity for distinguishing melanoma from nevus; however, ODM-specific validation is needed. Key warning signs include progressive tumor growth, unexplained vision loss, vitreous seeding, and intrinsic tumor vasculature. Evidence-based surveillance protocols recommend imaging every 3-6 months for the first 2 years after detection of high-risk features, then annually if stable. These findings support long-term surveillance with multimodal imaging and standardized quantification protocols.

Iris lesions encompass a broad spectrum of entities ranging from benign pigmentary variants to primary malignancies and secondary infiltrative or metastatic disease. Although many are discovered incidentally and remain asymptomatic, certain lesions may exhibit growth, seeding, hyphema, pigment dispersion, or angle involvement, leading to secondary glaucoma and vision loss. We synthesize contemporary evidence on melanocytic, non-melanocytic, and cystic iris lesions. We highlight a multimodal diagnostic approach incorporating slit-lamp biomicroscopy with serial photography, gonioscopy, iris transillumination, anterior segment optical coherence tomography, and high-frequency ultrasound biomicroscopy to characterize lesion architecture and define posterior extension. Ancillary testing, including dilated fundus examination and cross-sectional imaging, is discussed when ciliary body involvement or extra-iris disease is suspected. Management strategies are summarized, including surveillance thresholds, indications for biopsy, and treatment options for malignant or symptomatic lesions, with particular attention to prevention and control of secondary glaucoma.

A recent study described a distinctive subset of dysplastic nevi in older patients, genetically characterized by non-BRAFV600E driver mutations and frequent TERT promoter mutations. It has been proposed that these lesions overlap with the so-called lentiginous dysplastic nevi of the elderly. We explore this relationship in a series of 24 atypical lentiginous melanocytic proliferations, correlating with ex vivo dermoscopy, as well as immunohistochemical and molecular findings. We also discuss the utility of the MPATH-Dx tool to improve consensus for such lesions.

Small and medium sized congenital melanocytic nevi (CMN) have an overall low risk of malignant potential. This case demonstrates a pediatric patient with a small CMN positive for LINC00518 (LINC) and preferentially expressed antigen in melanoma (PRAME) on a non-invasive molecular test not yet validated in children. Although her nevus had not evolved, the availability of a molecular test and curiosity ultimately raised concern about this otherwise reassuring, stable CMN. This demonstrates the pitfalls of non-invasive testing in pediatric patients with CMN.