Journal of Cutaneous Pathology最新文献

Background: This study investigates the mutational profile of the KIT gene in primary and metastatic melanomas, highlighting the significance of genetic heterogeneity.

Methods: This research is a retrospective cohort that includes formalin-fixed and paraffin-embedded melanoma samples obtained from Hospital São Paulo, Brazil, between the years of 1996 and 2010. The research encompasses primary melanomas of the superficial spreading (SSM) and acral lentiginous (AL) subtypes and their metastases, using next-generation sequencing to explore genetic heterogeneity.

Results: Despite losing 57 samples due to quality issues, 27 samples from 20 patients were analyzed, revealing a nearly equal distribution between AL and SSM subtypes. Both histological subtypes revealed KIT gene variants, including previously undescribed variants and polymorphisms, emphasizing the role of such mutations in melanoma pathogenesis and the potential for targeted therapies. Tumor heterogeneity was also observed in both histological subtypes.

Conclusions: The study underscores the complexity of melanoma, driven by diverse mutational landscapes within and across tumors and advocates for personalized treatment approaches based on detailed molecular profiling. Despite limitations like sample size, this research lays the groundwork for further investigation into melanoma's genetic intricacies and therapeutic vulnerabilities.

Mesenchymal tumors may display morphologic and immunohistochemical overlap with melanocytic tumors, presenting a pitfall for misdiagnosis. We report a 62-year-old woman who presented with a recurrent dermal and subcutaneous tumor over the Achilles tendon 15 years following complete excision. Both the primary and the recurrent tumors were characterized by nests and sheets of epithelioid and spindle cells with eosinophilic cytoplasm and uniform ovoid nuclei. The tumor was positive for S100, SOX10, HMB45, cathepsin K, and p63 (weak), while negative for Melan-A, MiTF, smooth muscle actin, and desmin. Gene fusion analysis of the recurrent tumor revealed a NONO::TFE3 fusion which has been recently reported in two similar cutaneous cases. Our case highlights the potential of a NONO::TFE3 cutaneous epithelioid and spindle cell tumor to recur after a prolonged disease-free interval without evidence of high-grade transformation or distant metastasis. Our findings support its classification as a cutaneous mesenchymal neoplasm of intermediate malignancy.

NRAS Q61 mutations are driver genetic alterations associated with common melanocytic nevi. Herein, we describe a case of NRAS-mutant melanocytic tumor with a blue nevus-like morphology. A 71-year-old Japanese man presented with a 4.6-mm nodule on his back. Histopathological examination revealed a dense distribution of spindle-shaped melanocytes in the upper dermis and a sparse distribution of dendritic melanocytes in the mid-dermis. The vertical periadnexal extension reached the deep dermis at the center of the tumor. A small junctional component, hyperpigmentation, sclerotic stroma, mild nuclear atypia, and a few mitotic figures were observed. Immunohistochemical examination revealed no PRAME expression and preserved p16 expression. Diffuse RASQ61R immunoreactivity was observed in these tumor cells. Nuclear β-catenin expression was not observed. Targeted RNA sequencing revealed two mutations, NRAS c.182A>G (Q61R) and FGFR2 c.-157A>G, but no other pathogenic alterations such as BRAF, GNAQ, GNA11, CTNNB1, PRKAR1A, or IDH1 mutations or kinase gene fusions. The histopathology fits that of compound-type blue nevus, which is called "Kamino nevus"; however, this tumor was genetically considered to be on the spectrum of conventional acquired melanocytic nevi but not on that of blue nevi. Morphologically, NRAS-driven melanocytic nevi resemble blue nevi without IDH1^R132C coexistence.

Background: Activating BRAF gene alterations are central to melanocytic tumor pathogenesis. A small, emerging subset of melanocytic tumors driven by BRAF fusions has distinct therapeutic implications and has been described to have Spitzoid morphology patterns. However, such morphological patterns do not encompass all cases, and little is known about the functional molecular events.

Materials and methods: We conducted a retrospective search through our molecular archives to identify melanocytic tumors with BRAF fusions. We reviewed clinical, histopathological, and genomic features. We further explored transcriptomic and protein-level findings.

Results: Histopathologic patterns varied, with many cases without a distinctive pattern. We identified novel and diverse BRAF gene fusion partners. Differential transcriptomic analysis between low-risk BRAF fusion tumors and reference BRAF V600E tumors showed no differentially expressed genes. However, quantitatively stronger MAPK pathway activation of BRAF fusion tumors over BRAF V600E tumors was demonstrated by statistically significant stronger staining of p-ERK immunohistochemistry. Gene-specific RNA analysis shows comparable BRAF transcript levels between the two groups.

Discussion and conclusion: The quantitatively stronger activation of the MAPK pathway of BRAF fusion tumors, instead of qualitatively different transcriptomes, may account for the morphology difference from conventional BRAF V600E tumors. BRAF fusions likely act through dysregulated protein function rather than RNA upregulation related to the characteristics of the fusion partners.