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Immune checkpoint inhibitor therapy has demonstrated an overall survival benefit in patients with advanced melanoma. Though the significance of programmed death-ligand 1 (PD-L1) expression on melanoma cells as a predictive biomarker of response remains inconclusive, some reports indicate that a PD-L1 expression of <1% of tumor cells may be associated with better outcomes with dual immunotherapy. Adequate patient selection for combination therapy is critical given the higher frequency of adverse effects compared with monotherapy. Immunohistochemical (IHC) PD-L1 interpretation in tumor cells is challenging when inflammatory cells are present and cutoffs are low. We studied 36 metastatic melanoma biopsies from Immune checkpoint inhibitor-naive patients, previously stained and scored for PD-L1 IHC using the tumor proportion score (TPS). Cases were classified into 3 groups: <1%, 1% to 5%, and >5%. After de-coverslipping, SRY-related HMG-box-10 (SOX10) IHC was performed on PD-L1 IHC slides with a red chromogen, and subsequently scanned and scored by ≥2 dermatopathologists. This assessment determined that 25% of cases (9/36) had a TPS ≥ 1%, in contrast to the single IHC assay (63.8%). The majority of the 1-5% group (11/13, 84.6%) underwent a change of category to <1% TPS. In the >5% group, 60% of cases (6/10) were downgraded to <1% and 1% to 5% (4 and 2 cases, respectively). Our study suggests that PD-L1 IHC evaluation could benefit from dual PD-L1/SOX10 IHC. Dual IHC is expected to decrease the interference caused by PD-L1 expression on inflammatory cells, and digital imaging proves useful for the preservation and analysis of stains. Refining PD-L1 evaluation in metastatic melanoma may improve clinical decisions between single and combination immunotherapy, with potentially profound consequences in response and quality of life., Competing Interests: Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Identifying tumor characteristics that correlate with metastasis and survival in patients with conjunctival melanoma can potentially lead to better outcomes through a better selection of patients for adjuvant treatments including potentially life-saving new melanoma therapy. The objective of this study was to validate the conjunctival melanoma staging criteria in the American Joint Committee on Cancer (AJCC) Cancer Staging Manual (8th edition) and explore the prognostic importance of tumor thickness, histologic ulceration, and sentinel lymph node biopsy (SLNB) findings in patients with conjunctival melanoma. This is a case series of 88 consecutive patients with conjunctival melanoma. Clinicopathologic characteristics were analyzed. Associations between pathologic characteristics and outcomes were studied using Kaplan-Meier survival analysis. Local recurrence, lymph node metastasis, distant metastasis, and disease-specific survival (DSS) were the main outcome measures. The study included 56 women and 32 men; the median age was 62 years. At presentation, 41 patients had T1 disease, 23 had T2 disease, 23 had T3, and 1 had T4 disease. Sixty-six patients had invasive conjunctival melanoma (median thickness, 1.56 mm), 17 had conjunctival melanoma in situ, and in 5 patients, tumor thickness could not be determined. Overall, 22 patients had ulceration. In total, 31 patients underwent SLNB, and 4 had a positive sentinel lymph node (SLN). The median follow-up time was 46.6 months. Overall, 12 patients had nodal metastasis at presentation or during follow-up, 19 patients had distant metastasis at last follow-up, and 14 patients died of the disease. Tumor thickness and ulceration were associated with increased risks of nodal metastasis, distant metastasis, and death from the disease. Overall, greater clinical T category at presentation was associated with increased risks of distant metastasis and disease-related death; however, the risks of distant metastasis and disease-related death did not differ between T1 (bulbar) and T2 (nonbulbar) tumors or between T2c,d (caruncular) and T1-T2a,b (noncaruncular) tumors. In patients who underwent SLNB, a positive SLN was associated with worse distant metastasis free survival and DSS. Consideration should be given to adding ulceration and emphasizing tumor thickness as the main determinants of pathologic T category for conjunctival melanoma in future AJCC classifications. The significant association between a positive SLN and worse DSS highlights the importance of SLNB for prognosis in patients with conjunctival melanoma and selecting high-risk patients for adjuvant drug treatment.

Primary cutaneous gamma-delta (γδ) T-cell lymphoma is a rare disease that typically involves the dermis and subcutis. Cases of primary cutaneous T-cell lymphomas showing γδ phenotype and predominantly epidermotropic pattern (EγδTCL) are not well defined. In this series, cases of primary cutaneous T-cell lymphomas showing γδ phenotype were reviewed and classified as predominantly epidermotropic (EγδTCL) when >75% of lymphoma cells resided in the epidermis or predominantly dermal and/or subcutaneous (DSγδTCL). Clinical, pathologic, and immunophenotypic features were compared in 27 biopsies from 13 patients of EγδTCL and 13 biopsies from 7 patients of DSγδTCL. The lymphoma cells were diffusely positive for CD3 and T-cell receptor (TCR)γ, mostly positive for granzyme B and TIA-1, variably positive for CD8, CD7, and CD30, and negative for CD4 and TCRβ. Two patients with EγδTCL had dissemination to lymph nodes and 1 to the lung; 1 patient with DSγδTCL had gastrointestinal involvement. The median survival of patients with EγδTCL was not reached, and with a median follow-up of 19.2 months, 3/13 died. In contrast, the median survival of patients with DSγδTCL was 10 months, and after a median follow-up of 15.6 months, 5/5 died (P<0.01). EγδTCL is a rare presentation of cutaneous T-cell lymphoma that can be distinguished from DSγδTCL based on the extent of epidermotropism and has a better prognosis and longer median survival than DSγδTCL. However, although EγδTCL resembles mycosis fungoides clinically and histologically, a subset of EγδTCL is more likely to behave more aggressively than typical mycosis fungoides.

Poorly differentiated, cytologically malignant, spindle cell neoplasms of the skin may present a diagnostic challenge with important clinical consequences. In particular, the distinction between poorly differentiated cutaneous spindle cell squamous cell carcinoma (SpSCC) and atypical fibroxanthoma (AFX) remains controversial, but with important clinical implications: SpSCC exhibits an increased tendency for both local recurrence and metastasis compared with AFX. AFX is generally accepted as a diagnosis of exclusion based on negativity for a broad panel of immunohistochemical markers, including multiple cytokeratins, melanocytic markers, muscle markers, and vascular markers. As cytokeratins can also be occasionally lost in SpSCC, it would be of tremendous diagnostic value if there were additional specific markers to facilitate the distinction of lineage in this differential diagnostic context. Initial studies demonstrated p63 to be of utility in distinguishing AFX from SpSCC; however, p63 has proved to lack specificity, as it also exhibits variable reactivity in a subset of AFX. Recent studies have shown p40 immunohistochemistry to be a more specific marker than p63 for the designation of squamous differentiation in carcinomas involving other organ systems. In the current study, we define the utility of p40 immunohistochemistry among common cutaneous spindle cell malignancies, and, specifically, we compare the diagnostic accuracy of p40 and p63 in distinguishing AFX from SpSCC. We show that p40 and p63 exhibit comparable sensitivity, but p40 exhibits superior specificity in the distinction of AFX from SpSCC.

The diagnosis of benign versus malignant melanocytic proliferations remains an important challenge. The current diagnostic algorithm typically involves an assessment of histopathologic and immunohistochemical parameters by light microscopy. Recently, fluorescence in situ hybridization (FISH) was reported as a useful ancillary diagnostic tool in melanocytic lesions, but the utility of FISH in melanocytic tumors that are difficult to diagnose with standard morphologic analysis remains controversial. To address this issue, we collected 34 ambiguous melanocytic tumors for FISH testing (NeoGenomics). Before FISH testing, cases were designated as "favor benign" (n=24) or "favor malignant" (n=10) by a consensus group (up to 7 dermatopathologists) on the basis of clinical, histopathologic, and immunophenotypic parameters. FISH was positive in 3/24 "favor benign" lesions and in 5/10 "favor malignant" lesions. The histopathologic, immunophenotypic, and FISH parameters informing our diagnostic impression were correlated with the final consensus diagnosis and clinical follow-up; in all cases, the initial diagnosis remained unchanged. In this series, the sensitivity of FISH for the histopathologic diagnosis of melanoma was 50%, the specificity was 87.5%, the positive predictive value was 62.5%, and the negative predictive value was 80.7%. Follow-up information was available for 25 patients (17 benign and 8 malignant diagnoses). Among benign lesions, the mean follow-up was 16.8 months (range, 8 to 25 mo); no metastases have been reported to date. Among the malignant lesions, the mean follow-up was 14.6 months (range, 7 to 23 mo); a single lymph node metastasis was identified in a 4-year-old girl with a histopathologic diagnosis of melanoma, which was negative on FISH. In our experience, in the setting of a lesion with predominantly benign findings, a negative FISH test-given its high specificity-is a reassuring finding that supports a benign diagnosis. In contrast, a positive FISH test should be carefully interrogated in the context of the complete histopathologic findings.

Metanephric neoplasms are uncommon renal tumors that arise in both children and adults. They may be composed of small epithelial cells or benign stroma, or both, and are termed metanephric adenoma, metanephric stromal tumor, or metanephric adenofibroma, respectively. Thus far, these tumors have been known for their benign behavior. We present the case of a 21-year-old woman who developed a neoplasm composed of a renal epithelial component identical to metanephric adenoma combined with a malignant spindle cell sarcoma. The epithelial component was positive for pankeratin AE1/3, whereas the sarcomatous component was negative for epithelial markers and positive for vimentin, CD34, and CD117. No smooth muscle differentiation was apparent in the sarcoma by immunohistochemistry or ultrastructural analysis. By fluorescent in situ hybridization analysis of the sarcomatous component there was monosomy of the X chromosome, but no apparent variation from the normal diploid pattern for chromosomes 3, 7, 12, and 17. We conclude that the spectrum of metanephric neoplasia should be expanded to include malignant stromal variants, and we propose the term "metanephric adenosarcoma" for the present case.