Faculty Bibliography

INTRODUCTION/UNASSIGNED:Quantitative, multiplexed imaging is revealing complex spatial relationships between phenotypically diverse tumor infiltrating leukocyte populations and their prognostic implications. The underlying mechanisms and tissue structures that determine leukocyte distribution within and around tumor nests, however, remain poorly understood. While presumed players in metastatic dissemination, new preclinical data demonstrates that blood and lymphatic vessels (lymphovasculature) also dictate leukocyte trafficking within tumor microenvironments and thereby impact anti-tumor immunity. Here we interrogate these relationships in primary human cutaneous melanoma. METHODS/UNASSIGNED:We established a quantitative, multiplexed imaging platform to simultaneously detect immune infiltrates and tumor-associated vessels in formalin-fixed paraffin embedded patient samples. We performed a discovery, retrospective analysis of 28 treatment-naïve, primary cutaneous melanomas. RESULTS/UNASSIGNED:Here we find that the lymphvasculature and immune infiltrate is heterogenous across patients in treatment naïve, primary melanoma. We categorized five lymphovascular subtypes that differ by functionality and morphology and mapped their localization in and around primary tumors. Interestingly, the localization of specific vessel subtypes, but not overall vessel density, significantly associated with the presence of lymphoid aggregates, regional progression, and intratumoral T cell infiltrates. DISCUSSION/UNASSIGNED:We describe a quantitative platform to enable simultaneous lymphovascular and immune infiltrate analysis and map their spatial relationships in primary melanoma. Our data indicate that tumor-associated vessels exist in different states and that their localization may determine potential for metastasis or immune infiltration. This platform will support future efforts to map tumor-associated lymphovascular evolution across stage, assess its prognostic value, and stratify patients for adjuvant therapy.

BACKGROUND:Ongoing controversy exists regarding terminology used to describe atypical melanocytic nevi. Efforts to standardize nomenclature, including the 1992 NIH consensus conference, have been largely unsuccessful. Significant advances have revealed an increasingly detailed genetic picture of melanocytic neoplasms, including strong evidence for the existence of those with "intermediate" behavior. METHODS:We sent an electronic survey to dermatopathologists (n=846) to assess trends in nomenclature usage and attitudes toward developing new consensus nomenclature for atypical melanocytic nevi. RESULTS:There were 229 complete responses (27.1% response rate). The most used/preferred nomenclature was "dysplastic nevus" (43%/39%, respectively), followed by the NIH-recommended terminology (28%/26%). Three-tier grading systems were most heavily used/preferred (79%/63%). Dermatopathologists based in New England were most likely to use the NIH terminology, whereas "dysplastic nevus" or 'other' were most used elsewhere (p=0.029). Most (76%) expressed at least "moderate" enthusiasm for developing consensus nomenclature, with 47% "very" or "extremely" enthusiastic. CONCLUSION/CONCLUSIONS:Little has changed with the wide variation in terminology for atypical melanocytic nevi. There continues to be no one dominant terminology in use. However, there is enthusiasm for standardization. A new attempt at updated consensus nomenclature may be fruitful.

Cutaneous ganglioneuromas (GNs) are exceptionally uncommon tumors, and many reported cases describe association with overlying epidermal hyperplasia that may be interpreted as seborrheic keratosis (SK) or SK-like proliferation. We report 5 cases of cutaneous GN in adult patients; all of which were discovered incidentally in the immediate vicinity of epidermal hyperplasia. A review of the literature demonstrates the current-although likely imperfect-understanding of the etiopathogenesis of both SK and GN in the skin. We explore the putative pathophysiologies of other common, well-characterized skin lesions and, taking them into account, provide rationale for the coexistence of cutaneous GN with overlying SK and SK-like epidermal changes. However, we ultimately acknowledge a dilemma of causality and, given the rarity of their co-occurrence, objectively question whether occasional cameo appearances by GN lying subjacent to SK and SK-like hyperplasia may be due merely to chance.

Talimogene laherparepvec (T-VEC) has become an increasingly popular treatment option for surgically non-resectable, recurrent melanoma, usually of cutaneous metastases. The complete response (CR) rate has been reported to be ~20% with a median of ~9 months to achieve it. In real-world practice, decrease of tumor size often occurs rapidly within the first 2-3 months, while improvement of the pigmentation takes several more months. Such clinical observation of lasting pigmentation could be explained by tumorous melanosis-a histopathological term referring to the presence of a melanophage-rich inflammatory infiltrate without remaining viable tumor cells. Herein, we report six patients with metastatic cutaneous melanoma who were treated with T-VEC. Biopsies were performed after observing clinical responses in the injected tumors. Pathological evaluation demonstrated non-viable or absent tumor tissue with tumorous melanosis in all cases. To accurately assess response to therapy and potentially decrease unnecessary additional T-VEC treatments, serial biopsy of 'stable' lesions should be considered to assess the presence or absence of viable tumor.

Several mutations and gene fusions involved in the mitogen-activated protein kinase (MAPK) pathway have been reported in histiocytic neoplasms including Langerhans cell histiocytosis and non-Langerhans-cell histiocytosis (NLCH). We identified a GAB2::BRAF fusion in a cutaneous lesion from a 22-year-old woman who presented with central diabetes insipidus and red/brown papules on her face, oral mucosa, axilla, and groin. Skin biopsy showed a CD68+, S100-, and CD1a- histiocytic proliferation consistent with NLCH, best clinically classified as xanthoma disseminatum. Next-generation sequencing identified a GAB2::BRAF fusion involving exon 2 of GAB and exon 10 of BRAF. This case implicates a novel fusion in the MAPK signaling pathway, not previously reported in histiocytic neoplasms, as a possible driver of NLCH. Our findings underscore the utility of performing molecular studies on skin biopsy specimens with NLCH to help identify potential targets for therapy.

Dermatology heavily relies on photographs in its literature to depict diseases and demonstrate treatment modalities. Previous studies have established that general medical and dermatology textbooks have limited photographic representation of individuals with skin of color (SOC), even those diseases highly prevalent in these populations. As the US population continues to grow and diversify, there is an increase in individuals with SOC seeking cosmetic and procedural services. We set out to investigate the current trends of SOC representation in the surgical and cosmetic sections of current dermatology textbooks.

CD4⁺ T cells that recognize tumor antigens are required for immune checkpoint inhibitor efficacy in murine models, but their contributions in human cancer are unclear. We used single-cell RNA sequencing and T cell receptor sequences to identify signatures and functional correlates of tumor-specific CD4⁺ T cells infiltrating human melanoma. Conventional CD4⁺ T cells that recognize tumor neoantigens express CXCL13 and are subdivided into clusters expressing memory and T follicular helper markers, and those expressing cytolytic markers, inhibitory receptors, and IFN-γ. The frequency of CXCL13⁺ CD4⁺ T cells in the tumor correlated with the transcriptional states of CD8⁺ T cells and macrophages, maturation of B cells, and patient survival. Similar correlations were observed in a breast cancer cohort. These results identify phenotypes and functional correlates of tumor-specific CD4⁺ T cells in melanoma and suggest the possibility of using such cells to modify the tumor microenvironment.