Preferentially Expressed Antigen In Melanoma Research Articles

Estrogen Receptor Expression in DICER1-related Lesions is Associated with the Presence of Cystic Components.

DICER1 tumor predisposition syndrome results from pathogenic variants in DICER1 and is associated with a variety of benign and malignant lesions, typically involving kidney, lung, and female reproductive system. Over 70% of sarcomas in DICER1 tumor predisposition syndrome occur in females. Notably, pediatric cystic nephroma (pCN), a classic DICER1 tumor predisposition syndrome lesion, shows estrogen receptor (ER) expression in stromal cells. There are also renal, hepatic, and pancreatic lesions unassociated with DICER1 tumor predisposition syndrome that have an adult female predominance and are characterized/defined by ER-positive stromal cells. Except for pCN, the expression of ER in DICER1-associated lesions remains uninvestigated. In the present study, ER expression was assessed by immunohistochemistry in 89 cases of DICER1-related lesions and 44 lesions lacking DICER1 pathogenic variants. Expression was seen in stromal cells in pCN and pleuropulmonary blastoma (PPB) types I and Ir, whereas anaplastic sarcoma of kidney and PPB types II and III were typically negative, as were other solid tumors of non-Müllerian origin. ER expression was unrelated to the sex or age of the patient. Expression of ER showed an inverse relationship to preferentially expressed antigen in melanoma (PRAME) expression; as lesions progressed from cystic to solid (pCN/anaplastic sarcoma of kidney, and PPB types I to III), ER expression was lost and (PRAME) expression increased. Thus, in DICER1 tumor predisposition syndrome, there is no evidence that non-Müllerian tumors are hormonally driven and antiestrogen therapy is not predicted to be beneficial. Lesions not associated with DICER1 pathogenic variants also showed ER-positive stromal cells, including cystic pulmonary airway malformations, cystic renal dysplasia, and simple renal cysts in adult kidneys. ER expression in stromal cells is not a feature of DICER1 perturbation but rather is related to the presence of cystic components.

Targeting PRAME for acute myeloid leukemia therapy.

Despite significant progress in targeted therapy for acute myeloid leukemia (AML), clinical outcomes are disappointing for elderly patients, patients with less fit disease characteristics, and patients with adverse disease risk characteristics. Over the past 10 years, adaptive T-cell immunotherapy has been recognized as a strategy for treating various malignant tumors. However, it has faced significant challenges in AML, primarily because myeloid blasts do not contain unique surface antigens. The preferentially expressed antigen in melanoma (PRAME), a cancer-testis antigen, is abnormally expressed in AML and does not exist in normal hematopoietic cells. Accumulating evidence has demonstrated that PRAME is a useful target for treating AML. This paper reviews the structure and function of PRAME, its effects on normal cells and AML blasts, its implications in prognosis and follow-up, and its use in antigen-specific immunotherapy for AML.

Double Immunohistochemical Labelling of PRAME and Melan A in Slow Mohs Biopsy Margin Assessment of Lentigo Maligna and Lentigo Maligna Melanoma.

Introduction: Lentigo maligna (LM) and lentigo maligna melanoma (LMM) predominantly affect the head and neck areas in elderly patients, presenting as challenging ill-defined pigmented lesions with indistinct borders. Surgical margin determination for complete removal remains intricate due to these characteristics. Morphological examination of surgical margins is the key form of determining successful treatment in LM/LMM and underpin the greater margin control provided through the Slow Mohs micrographic surgery (SMMS) approach. Recent assessments have explored the use of immunohistochemistry (IHC) markers, such as Preferentially Expressed Antigen in Melanoma (PRAME), to aid in LM/LMM and margin evaluation, leveraging the selectivity of PRAME labelling in malignant melanocytic neoplasms. Methods: A Novel double-labelling (DL) method incorporating both PRAME and MelanA IHC was employed to further maximise the clinical applicability of PRAME in the assessment of LM/LMM in SMMS biopsies. The evaluation involved 51 samples, comparing the results of the novel DL with respective single-labelling (SL) IHC slides. Results: The findings demonstrated a significant agreement of 96.1% between the DL method and SL slides across the tested samples. The benchmark PRAME SL exhibited a sensitivity of 91.3% in the SMMS specimens and 67.9% in histologically confirmed positive margins. Discussion: This study highlights the utility of PRAME IHC and by extension PRAME DL as an adjunctive tool in the assessment of melanocytic tumours within staged excision margins in SMMS samples.

Expression of Immunotherapy Target PRAME in Cancer Correlates with Histone H3 Acetylation and Is Unrelated to Expression of Methylating (DMNT3A/3B) and Demethylating (TET1) Enzymes.

Background/Objectives: Preferentially expressed antigen in melanoma (PRAME), a member of the cancer testis antigen family, is a promising target for cancer immunotherapy. Understanding the epigenetic mechanisms involved in the regulation of PRAME expression might be crucial for optimizing anti-PRAME treatments. Methods: Three malignancies of different lineages (sinonasal melanoma, testicular seminoma, and synovial sarcoma), in which immunohistochemical (IHC) reactivity for PRAME is a common yet variable feature, were studied. The expression of PRAME, ten-eleven translocation demethylase 1 (TET1), and DNA methyltransferase (DNMT) 3A and 3B were evaluated using immunohistochemistry. Moreover, the expression of two epigenetic marks, 5-hydroxymethylcytosine (5hmC) and histone 3 acetylation (H3ac), was tested. Results: All PRAME-positive tumors expressed medium-to-high levels of H3ac but differed considerably with respect to other markers. In seminomas, PRAME expression correlated with TET1, but in melanomas and synovial sarcomas, it correlated with both DNMTs and DNMT3A, respectively. Conclusions: PRAME expression was not determined by a balance between the global expression of DNA methylating/demethylating enzymes. However, histone acetylation may be one of the epigenetic mechanisms involved in PRAME regulation. Thus, the therapeutic combination of histone deacetylase inhibitors and PRAME immunotherapy merits further investigation.

PRAME Expression: A Target for Cancer Immunotherapy and a Prognostic Factor in Uveal Melanoma.

Uveal melanoma (UM) is a rare disease with a high mortality, and new therapeutic options are being investigated. Preferentially Expressed Antigen in Melanoma (PRAME) is a cancer testis antigen, expressed in the testis, but also in cancers, including uveal melanoma. PRAME is considered a target for immune therapy in several cancers, and PRAME-specific T cell clones have been shown to kill UM cells. We studied the literature on PRAME expression in hematological and solid malignancies, including UM, and its role as a target for immunotherapy. The distribution of tumor features was compared between PRAME-high and PRAME-low UM in a 64-patient cohort from the Leiden University Medical Center (LUMC) and in the Cancer Genome Atlas (TCGA) cohort of 80 cases and differential gene expression analysis was performed in the LUMC cohort. PRAME is expressed in many malignancies, it is frequently associated with a negative prognosis, and can be the target of T cell receptor (TCR)-transduced T cells, a promising treatment option with high avidity and safety. In UM, PRAME is expressed in 26% to 45% of cases and is correlated with a worse prognosis. In the LUMC and the TCGA cohorts, high PRAME expression was associated with larger diameter, higher Tumor-Node-Metastasis (TNM) stage, more frequent gain of chromosome 8q, and an inflammatory phenotype. We confirm that PRAME is associated with poor prognosis in UM and has a strong connection with extra copies of 8q. We show that PRAME-specific immunotherapy in an adjuvant setting is promising in treatment of malignancies, including UM.

Shedding light on PRAME expression in dysplastic nevi: a cohort study.

Dysplastic nevi represent one of the least agreed-upon entities in dermatopathology despite the existence of established criteria. This study explores preferentially expressed antigen in melanoma (PRAME) in dysplastic nevi, an uncharted area. We examined 22 common melanocytic nevi (CMN), 20 cutaneous melanomas (CM), 48 low-grade dysplastic nevi (LG-DN), and 40 high-grade dysplastic nevi (HG-DN). PRAME was immunohistochemically assessed using a five-tiered system (0 to 4 +). Among CMN, 59% scored 0, 32% scored 1 + , and 9% scored 2 + . CM had score 2 + and 4 + in 11% and 89% of cases, respectively. Among LG-DN, 38% presented score 0, 31% score 1 + , 17% score 2 + , 8% score 3 + , and 6% score 4 + . Thirty per cent of HG-DN demonstrated a score 0, 30% with score 1 + , 15% score 2 + , 10% score 3 + , and 15% score 4 + . Compared to CMN and CM, LG-DN and HG-DN showed heterogeneous expression profiles of PRAME. PRAME positivity effectively distinguished HG-DN from CM with 85% specificity and 80% sensitivity (p < 0.0001). Predictive values were 87% (negative) and 76% (positive). Furthermore, a trend of increased PRAME expression from LG-DN to HG-DN was observed. However, the applicability of PRAME in the differential diagnosis of dysplastic lesions remains unclear as can yield conflicting results with morphology, which remains the primary diagnostic tool for melanocytic lesions.

Androgen Receptor Immunohistochemistry is Superior to PRAME for the Differentiation of Sebaceous Carcinoma From Primary Cutaneous Basaloid Mimics.

Cutaneous sebaceous neoplasia comprises a spectrum of disease ranging from benign adenomas to malignant carcinomas. The hallmark of these lesions is sebaceous differentiation. However, poorly-differentiated sebaceous carcinoma (SC), which lacks significant overt sebaceous differentiation, can show morphologic overlap with a variety of other basaloid cutaneous neoplasms. The accurate classification of SC is essential not only for diagnosis, but also because of the potential association with Muir-Torre syndrome. Androgen receptor (AR) is a sensitive, but not entirely specific immunohistochemical marker that has been used for the diagnosis of SC. PReferentially expressed Antigen in MElanoma (PRAME) demonstrates strong cytoplasmic labeling of mature sebocytes and has been reported to be expressed in a variety of sebaceous neoplasms, including in the basaloid cell component. Therefore, we sought to compare the diagnostic use of cytoplasmic PRAME expression with that of AR for the distinction of SC from a cohort of basaloid cutaneous mimics; namely basal cell carcinoma, basaloid squamous cell carcinoma, pilomatricoma, cutaneous lymphadenoma, and extra-mammary Paget disease. We report that cytoplasmic PRAME expression is uncommon in poorly differentiated SC, and although specific, it shows very low sensitivity (22%). In contrast, AR was moderately sensitive (66%) and highly specific (92%) for the distinction of SC from basaloid mimics. These attributes, in addition to the nuclear expression of AR in the sebocytic and basaloid components of SC, suggest that AR is superior to PRAME for the diagnosis of SC.

A Comparison of Preferentially Expressed Antigen in Melanoma Immunohistochemistry and Diagnostic Gene Expression-Profiling Assay in Challenging Melanocytic Proliferations.

Most melanocytic tumors are classified as benign or malignant based on clinical morphology, histology, and immunohistochemical (IHC) analysis. A subset of more challenging cases with ambiguous features may require further evaluation with established ancillary diagnostic molecular studies, including fluorescence in situ hybridization and/or single nucleotide polymorphism array, to increase diagnostic certainty. More recently, a diagnostic gene expression-profiling (GEP) assay and an IHC stain for the detection of PRAME (PReferentially expressed Antigen in MElanoma) have been developed. The use of PRAME IHC has been validated in cases of unequivocal and ambiguous melanocytic proliferations via comparing results with fluorescence in situ hybridization and/or single nucleotide polymorphism array. A study comparing performance metrics of PRAME IHC and diagnostic GEP has not been previously published. Herein, we evaluated the use of PRAME IHC in 55 melanocytic tumors with challenging histomorphology by comparing the results with diagnostic GEP and final histomorphologic diagnosis. Intertest agreement occurred in 88% of cases. PRAME IHC supported the final diagnosis in 89% of cases with a sensitivity of 79%, specificity of 95%, and positive predictive value of 88.2%. GEP agreed with the final diagnosis in 88% of cases with a sensitivity of 65%, 97% specificity, and positively predicted melanoma in 91.7% of cases. Because the results of this study align with past publications evaluating the performance metrics of PRAME IHC, showing it to be as sensitive as and more cost effective than all other ancillary molecular tests, we propose the use of PRAME IHC as the optimal first-line diagnostic tool for ambiguous melanocytic proliferations.

Periocular Sebaceous Carcinoma: A Case Audit from the National Specialist Ophthalmic Pathology Service in Liverpool from 2009 to 2022 to Assess the Diagnostic Utility of PRAME Expression

Introduction: Periocular sebaceous carcinoma (PSC) remains a common diagnostic pitfall both clinically and histomorphologically. PRAME (preferentially expressed antigen in melanoma) has been studied in the various neoplasms as proposed as diagnostic and therapeutic markers. PRAME is expressed in normal sebaceous units and in some sebaceous lesions; however, its utility in sebaceous carcinoma diagnosis has not yet been extensively investigated. We conducted a 13-year retrospective review of the patients diagnosed with PSC at the National Specialist Ophthalmic Pathology Service in Liverpool. Herein, we report the histomorphological and immunohistochemical (IHC) features of these tumors, particularly PRAME expression in this cohort. Methods: Thirty-one PSC cases diagnosed between 2009 and 2022 were retrieved from the histopathology archives. Twenty cases diagnosed as invasive PSC and 11 cases with in situ PSC were included. The hematoxylin and eosin (H&E) slides and previously performed IHC slides were reviewed; clinical information data were obtained. Cases with an adequate tissue were also stained for PRAME (preferentially expressed antigen in melanoma) and adipophilin (if not already performed). Results: In total, there were 24 females and 7 males diagnosed with PSC, ranging from 55 to 90 years (median, 78 years). The types of specimens received were 11 conjunctival mapping biopsies, 19 excisions/wedge resections, and 1 orbital exenteration. The eyelid was the commonest site involved (n = 24), followed by eyelid with conjunctiva (3), and conjunctiva alone (4). All patients presented with the clinical suspicion of malignancy. Histologically, 11 invasive PSC (55%) exhibited poorly differentiated morphology, composed of predominantly atypical basaloid cells with minimal sebocytic differentiation; 9 cases (45%) were moderately differentiated with noticeable finely multivacuolated cytoplasm; and 3 (15%) showed associated comedo necrosis. Most invasive PSC showed moderate-to-brisk mitotic activities. Of those cases with available immunostains (n = 31), 25 (80.6%) expressed adipophilin; 18 (58.1%) Ber-EP4; 14 (45.2%) epithelial membrane antigen (EMA); and 5 (16.1%) both androgen receptor and perforin positivity. PRAME expression was seen in normal sebaceous glands; however, only (5/19; 26%) of invasive PSC showed focal weak-to-moderate PRAME positivity, and mostly in moderately differentiated tumors. None of the in situ PSCs were PRAME-positive. Conclusions: Most PSCs are moderate-to-poorly differentiated. Although PRAME is expressed in normal sebaceous units, it appears less useful as diagnostic marker for PSC, especially in poorly differentiated tumors. In difficult cases, panels of IHC studies (adipophilin, Ber-EP4, and EMA) achieve a definitive diagnosis.

Expression of Preferentially Expressed Antigen in Melanoma, a Cancer/Testis Antigen, in Carcinoma In Situ of the Urinary Tract.

Carcinoma in situ (CIS) of the urinary tract comprises 1-3% of all urothelial malignancies and is often a precursor to muscle-invasive urothelial carcinoma (UC). This study aimed to examine the expression profiles of preferentially expressed antigen in melanoma (PRAME), a cancer/testis antigen, and assess its diagnostic and therapeutic applications in CIS, given that its expression in UC has been minimally studied and has not yet been analyzed in CIS. We selected consecutive patients with CIS who underwent biopsy and/or transurethral tumor resection at the Osaka Medical and Pharmaceutical University Hospital. Immunohistochemical staining for PRAME and p53 was performed. Overall, 53 patients with CIS (6 females and 47 males) were included. Notably, PRAME expression was observed in 23 of the 53 patients (43.4%), whereas it was absent in the non-neoplastic urothelial epithelium. Furthermore, no correlation was found between PRAME expression and aberrant p53 expression. Therefore, PRAME expression may serve as a useful marker for CIS of the urinary tract. Furthermore, PRAME may be a candidate for the novel therapeutic target for standard treatment-refractory CIS patients.

PRAME Immunohistochemistry for Distinguishing Vulvar and Vaginal Melanoma From Benign Melanocytic Nevi

Vulvovaginal melanoma (VVM) is a rare but deadly disease, accounting for 5% of all vulvar malignancies, with a 5-yr survival rate of only 47% for all stages of the disease. VVM is a distinct subset of melanoma, with a unique genomic profile and underlying pathogenesis unassociated with sun exposure. Distinguishing these rare malignancies from very common pigmented lesions of the vulva and vagina is challenging as histologic features often overlap between entities. PReferentially expressed Antigen in MElanoma (PRAME) is a melanoma-associated protein, and immunohistochemistry (IHC) for PRAME distinguishes cutaneous, oral mucosal, and retinal melanoma from atypical nevi. Given the biological differences between VVM and cutaneous melanoma, the utility of PRAME IHC for the diagnosis of VVM is unknown. We accrued a cohort of 20 VVM and 21 benign vulvar melanocytic nevi. We found that nuclear PRAME IHC staining with 4+ intensity was present in 85% of the VVM and 0% of the nevi. With the assistance of PRAME IHC, we found evidence of close or positive margin involvement in 3 of 10 cases where margins were originally diagnosed as negative for melanoma in situ. Our study is the first to assess PRAME IHC in a cohort of VVM cases and provides confidence for using PRAME IHC to assist with diagnosis and margin assessment in this rare disease.

Clear Cell Sarcoma masquerading as Malignant Melanoma: A Case Report

Abstract Introduction/Objective Clear cell sarcoma (CCS) is a rare and diagnostically challenging soft tissue tumor that can mimic other malignancies with melanocytic differentiation. Histologically it shows diffuse sheets of clear cells with scattered melanin pigment in a subset of cases. Other morphologies have been described but contain atleast a portion of clear cell features. We report a case of CCS with unusual histomorphology, highlighting the importance of incorporating cytogenetic and immunohistochemical studies to accurately diagnose this tumor. Methods/Case Report We present a case of a 49-year-old male with a left lateral knee mass associated with pain and swelling for one year. A core biopsy revealed a diffuse proliferation of pleomorphic spindle and atypical epithelioid cells. These atypical cells exhibited intranuclear vacuoles, variable prominent nucleoli, abundant dusky cytoplasm, and increased mitotic activity. Immunohistochemical studies were positive for S100, SOX10, and Melan-A (patchy), suggesting a melanocytic differentiation. However, no expression of Preferentially Expressed Antigen in Melanoma (PRAME) or BRAF V600E mutation was noted. Given the clinical history and lack of cutaneous melanocytic lesion, clear cell sarcoma was considered in the differential diagnosis. Fluorescence in situ hybridization (FISH) studies revealed Ewing sarcoma region 1 (EWSR1) gene rearrangement in neoplastic cells, confirming the diagnosis of CCS. Results (if a Case Study enter NA) NA Conclusion The tumor lacked definitive histologic features including clear cell features, demonstrating the variability in histomorphology that can be encountered with CCS. Distinction of CCS from melanoma is of clinical significance as treatment significantly differs. Accurate diagnosis requires the incorporation of cytogenetic and immunohistochemical studies to differentiate it from melanocytic neoplasms. Variability in histomorphology of CCS can pose, as is evident in our case, as a diagnostic pitfall, and CCS should be considered in the differential diagnosis of unusual non-cutaneous melanocytic proliferations that lack clear cell features and show compelete spindle and epithelioid morphology.

Potent and Target Specific Cytotoxicity of PRAME TCR Mimic CAR T Cells in KMT2A-Rearranged AML Patient-Derived Xenograft Model

Chimeric antigen receptor (CAR) T cell therapy was a resounding success in CD19+ ALL despite the fact that it is essential for B-cell maturation because it is not expressed during normal myeloid hematopoiesis. Normal and leukemic B-cells are targeted by CD19+ CAR T-cells without causing myeloid hematopoietic toxicity. Advancing such therapy to acute myeloid leukemia (AML) has been challenging in part due to a paucity of “dispensable” targets or targets whose expression is limited to the leukemic cells. Using a large AML and normal hematopoiesis transcriptome database, we pursued discovery of “AML-Restricted Targets”; genes that are silent in normal hematopoiesis but expressed in AML. This broad discovery effort yielded a library of AML-restricted targets that included PRAME (Preferentially Expressed Antigen in Melanoma), an intracellular protein expressed via MHC on the cell surface, to be a highly expressed in AML including the aggressive KMT2A-rearranged (KMT2A-r) AML. We used a TCR mimic (mTCR) antibody, which recognizes the PRAME peptide/HLA-A2 complex on the tumor cell surface, to develop a PRAME directed TCR mimic CAR T (PRAME mTCRCAR T) for pre-clinical studies. Studies in cell lines and CDX models have shown significant efficacy of this CAR T (Kirkey, Bld Adv. 2022). To conduct final IND-enabling studies, we generated a KMT2A-r HLA-A2+/PRAME+ patient-derived xenograft (PDX) model to treat with PRAME mTCRCAR T-cells. Here we demonstrate the in vivo activity of PRAME mTCRCAR T cells against this unique PDX AML model. VL and VH sequences from the PRAME specific TCR mimic antibody (Pr20) were used to construct the single-chain fragment variable domain into the 41-BB/CD3ζ CAR vector. The PDX model was derived from a PRAME +/HLA-A2 + pediatric patient with KMTA2-r AML. PDX cells were transduced with lentiviral ffluciferase for noninvasive bioluminescent IVIS imaging to monitor leukemic progression. Mice were transplanted with 1x10 6 PDX leukemia cells then 1 week later, PDX leukemia-bearing mice were treated with unmodified T cells or PRAME mTCRCAR T cells at 5x10 6 cells (1:1 CD4:CD8) per mouse. Leukemia burden was measured by IVIS imaging and regular peripheral blood analysis. Mice who received unmodified T cells had rapid disease progression by day 50 and all died by day 105. In contrast, PRAME mTCRCAR T-treated mice rapidly cleared disease and all remained alive and leukemia-free &amp;gt;180 days post-treatment (p=0.001). Average leukemia burden in the control cohort was 3.5% at week 6 and 41.75% at week 11, while no leukemia was detected following CAR T-cell treatment. In addition, the control arm had a marked expansion of leukemia with a 7.75- and 429.6-fold increase in radiance by IVIS at 6 and 11 weeks post-treatment, respectively. No significant increase in radiance was seen in the PRAME mTCRCAR T cell treated group. We further evaluated hematopoietic toxicity of PRAME mTCRCAR T cells in humanized mice. Sub-lethally irradiated NSG-SGM3 mice were reconstituted with HLA-A2+ CD34 selected human cord blood stem cells with simultaneous and allowed to engraft. Human hematopoietic cell engraftment was evaluated following treatment with unmodified T cells vs. PRAME mTCRCAR T cells. Evaluation of human CD45+ cells in the peripheral blood via flow cytometry showed no difference in the levels of hematopoietic engraftment in mice treated with PRAME mTCRCAR T cell (8%) vs. unmodified T cells (6%) vs. an untreated control cohort (5%), demonstrating lack of toxicity of PRAME mTCRCAR T cells against HLA-A2 hematopoiesis. We demonstrate that PRAME mTCRCAR T cells can irradicate AML in a target specific manner in aggressive KMT2A-r AML without toxicity. We show potent efficacy with eradication of leukemia in PDX-bearing mice following treatment with PRAME mTCRCAR T cells resulting in prolonged survival, without hematopoietic toxicity. These results provide strong rationale for advancing this therapeutic approach to clinical development.

Combined WNT-activated deep-penetrating/plexiform melanocytoma: insights into clinicopathological andmolecular characterization.

A combined deep-penetrating tumour redefined as WNT-activated deep-penetrating/plexiform melanocytoma (DPM), may pose challenging clinical and histological diagnoses. To review the clinicopathological characteristics of combined DPMs and characterize the molecular profile of atypical and malignant forms. The study included 51 patients with combined DPMs diagnosed at the Hospital Clinic of Barcelona and the University of Florence between 2012 and 2020. Clinical data, dermoscopy images (when available) and histological characteristics were reviewed. Immunohistochemistry for β-catenin, LEF1, HMB45, Ki67, p16 and PRAME (preferentially expressed antigen in melanoma) was performed. Atypical forms underwent next-generation sequencing (NGS) panel analysis, including driver genes implicated in DPMs, TERT-promoter (p) mutations and the investigation of the 9p21 locus via fluorescence in situ hybridization. Among the 51 patients (32 females and 19 males, age range 4-74 years), 68% with available clinical data (15/22) were initially suspected of having melanoma. Except for one patient, complete excision resulted in no recurrences or metastases. One patient who had an incompletely excised combined DPM developed a lymph node melanoma metastasis 10 years later. In the 51 patients, 10 samples (20%) showed atypical histological features; 7 (14%) exhibited a significant loss of p16 expression; and 2 (4%) showed a high-proliferative index (Ki67 over 5%). NGS analysis in 11 patients revealed a double mutation BRAFV600E and exon 3 CTNNB1; no TERTp mutations were detected. Clinical suspicion of melanoma is common in combined DPMs, but malignant progression is infrequent in tumours lacking high-grade atypia or proliferation. These findings are congruent with the consideration of these lesions as intermediate-grade tumours or melanocytomas.

Cutaneous squamous cell carcinoma with osteoclast-like giant cells in an 87-year-old male

Cutaneous Squamous Cell Carcinoma (SCC) with Osteoclast-Like Giant Cells (OLGCs) is a rare finding, with only 11 previous cases reported in the literature. The origin of the OLGC within carcinomas has been debated, and there are two prevailing theories regarding the cell origin. We report the 12th case of SCC with OLGCs, discuss the two theories, and analyze the common features among all twelve cases. Ultimately, there appears to be an association between OLGCs and poorly differentiated cutaneous squamous cell carcinomas. Consequently, OLGCs should lead to an increased index of suspicion, as they may be a predictor of poor outcomes. If OLGCs are identified on histology, the pathologist should consider the addition of Preferentially-expressed Antigen in Melanoma (PRAME) immunostaining as a means of more accurately determining the prognosis. In conjunction with clinical features, histology should guide clinical recommendations and may warrant chemoprevention with systemic retinoids in high-risk individuals.

PReferentially Expressed Antigen in MElanoma Expression in Uterine and Ovarian Carcinosarcomas.

Carcinosarcoma (CS) is an aggressive form of gynecologic malignancy that accounts for ~5% of carcinomas in the endometrium and ovaries. There has been no significant improvement in survival over the last decades despite additional treatment options. PReferentially Expressed Antigen in MElanoma (PRAME) is an immunotherapy target used for the treatment of several solid tumors. We explored the PRAME protein expression levels in ovarian and uterine CS (n = 29). The expression levels were recorded by H-score (percentage of positively stained cells multiplied by staining intensity) in carcinomatous and sarcomatous components separately and compared by paired t-test. The marker expression levels of ovarian and uterine CS were tested against each other in the CS group. Sarcoma-predominant samples (>50% of the sampled tissue) were compared with samples without predominant sarcomatous components by a 2-sample pooled t-test. In addition, high-grade carcinomatous components of CS samples were tested against low-grade endometrioid carcinoma (International Federation of Gynecology and Obstetrics grades 1 and 2; n = 13), and sarcomatous components against uterine leiomyosarcoma (n = 14). There was no significant difference between any subgroups except for sarcomatous elements of CS and leiomyosarcoma ( P < 0.001). A weak positive correlation was found between H-scores of carcinomatous and sarcomatous components ( P = 0.062, r = 0.36). In the ovarian CS group, there was a moderate inverse correlation between age and the mean H-score of the carcinomatous component ( r = -0.683, P = 0.02). Our results further support PRAME overexpression in gynecologic cancers, including CS with similar expression levels in epithelial and mesenchymal components. PRAME might have a role in epithelial-mesenchymal transition in this group of cancers.

Immunohistochemistry for PRAME in Dermatopathology.

Preferentially expressed antigen in melanoma (PRAME) is a tumor-associated antigen first identified in a melanoma patient and found to be expressed in most melanomas as well as in variable levels in other malignant neoplasms of epithelial, mesenchymal, or hematolymphoid lineage. Detection of PRAME expression in formalin-fixed paraffin-embedded tissue is possible by immunohistochemistry (IHC) with commercially available monoclonal antibodies. In situ and invasive melanoma frequently show a diffuse pattern of nuclear PRAME immunoreactivity which contrasts with the infrequent and typically nondiffuse staining seen in nevi. In many challenging melanocytic tumors, results of PRAME IHC and other ancillary tests correlate well, but not always: The tests are not interchangeable. Most metastatic melanomas are positive for PRAME, whereas nodal nevi are not. Numerous studies on PRAME IHC have become available in the past few years with results supporting the value of PRAME IHC as an ancillary tool in the evaluation of melanocytic lesions and providing insights into limitations in sensitivity and specificity as well as possible pitfalls that need to be kept in mind by practicing pathologists.

Comparison of Melanocyte-Associated Immunohistochemical Markers in Acral Lentiginous Melanoma and Acral Benign Nevi.

Acral lentiginous melanoma (ALM) is a relatively rare clinicopathologic subtype of cutaneous malignant melanoma, but it is the most common type of melanoma among Asians. Although the research to identify immunohistochemical (IHC) markers to differentiate nevi from melanoma is being conducted, specific markers for ALM are not well-known. Therefore, we aimed to analyze and compare the differences in the expression of melanocyte-associated IHC markers between ALM and acral benign nevi (ABN). Two independent groups of 53 and 19 paraffin-embedded specimens (from patients with pathologically confirmed ALM and ABN, respectively) were subjected to IHC staining for MART-1, preferentially expressed antigen in melanoma (PRAME), SOX10, HMB-45, Ki-67, and p16. We performed a quantitative analysis of PRAME, SOX10, KI-67, and p16 expression and gradient pattern analysis of HMB-45 expression for each specimen. The PRAME (60.1% and 28.5%, P < 0.05) and Ki-67 (7.8% and 3.5%, P < 0.05) expression levels were significantly higher in the ALM group than in the ABN group. The p16 expression was significantly lower (14.2% and 19.4%, P < 0.05), and the absence of HMB-45 gradient was more frequent in the ALM group than in the ABN group. However, no statistical significance was noted in SOX10 (54.8% and 44.7%). Receiver operating characteristic curves showed that PRAME had the highest area under the curve value. In summary, among various IHC markers, PRAME was the most valuable marker for the diagnosis of ALM; however, further large-scale studies are needed to validate these findings.

Expression of Melan-A in cutaneous granular cell tumours: a diagnostic pitfall

Morphological overlap exists between cutaneous granular cell tumours (GCT) and malignant melanoma, with the melanocyte-specific markers HMB45 and Melan-A commonly used to support the diagnosis of melanoma. We recently encountered several cases of GCT in our practice showing strong expression of Melan-A. The aim of this study was to establish the prevalence of positive immunohistochemical staining for Melan-A and HMB45 in a series of unequivocal GCTs. We also aimed to assess the prevalence of staining for PRAME (PReferentially expressed Antigen in MElanoma), a marker expressed in >80% of primary melanomas as well as many non-melanocytic tumours. A total of 20 cutaneous/subcutaneous GCTs were evaluated using Melan-A, HMB45 and PRAME immunohistochemistry. Staining for Melan-A and HMB45 was scored using a semiquantitative scale from 0 (absent) to 3+ (staining present in >50% of tumour cells). PRAME expression was recorded as either positive (>75% of cell nuclei staining) or negative. Melan-A expression was observed in four GCTs (20%), with strong and diffuse (3+) staining seen in two cases (10%), both from anogenital areas. Weak patchy nuclear PRAME expression was seen in every case, interpreted to be negative. HMB45 was also negative in all cases (100%). Our study demonstrates that Melan-A expression can be strong and diffuse in a subset of otherwise unequivocal cutaneous GCTs, which may cause diagnostic confusion with malignant melanoma. HMB45 and PRAME did not stain any of the GCTs in our series.

PRAME immunohistochemistry compared to traditional FISH testing in spitzoid neoplasms and other difficult to diagnose melanocytic neoplasms.

PRAME (PReferentially expressed Antigen in Melanoma) is a gene first identified in melanoma. It has been proposed as a useful marker to differentiate melanoma from benign melanocytic neoplasms. Recently genomic testing using fluorescence in situ hybridization has been used to aid in the diagnosis of difficult melanocytic neoplasms. We have compared PRAME staining to FISH testing results in 83 difficult to classify melanocytic neoplasms which showed spitzoid histologic features. A relatively low sensitivity of 29.6% and high specificity of 76.8% is seen with PRAME staining as compared to genomic testing with fluorescence in situ hybridization. This study highlights the limitations of PRAME staining in spitzoid neoplasms.