PRAME immunohistochemistry is useful in the evaluation of conjunctival melanomas, nevi, and primary acquired melanosis

A Multicenter Study Validates the WHO 2022 Classification for Conjunctival Melanocytic Intraepithelial Lesions With Clinical and Prognostic Relevance

Several nomenclature and grading systems have been proposed for conjunctival melanocytic intraepithelial lesions (C-MIL). The fourth "WHO Classification of Eye Tumors" (WHO-EYE04) proposed a C-MIL classification, capturing the progression of noninvasive neoplastic melanocytes from low- to high-grade lesions, onto melanoma in situ (MIS), and then to invasive melanoma. This proposal was revised to the WHO-EYE05 C-MIL system, which simplified the high-grade C-MIL, whereby MIS was subsumed into high-grade C-MIL. Our aim was to validate the WHO-EYE05 C-MIL system using digitized images of C-MIL, stained with hematoxylin and eosin and immunohistochemistry. However, C-MIL cases were retrieved from 3 supraregional ocular pathology centers. Adequate conjunctival biopsies were stained with hematoxylin and eosin, Melan-A, SOX10, and PReferentially expressed Antigen in Melanoma. Digitized slides were uploaded on the SmartZoom platform and independently scored by 4 ocular pathologists to obtain a consensus score, before circulating to 14 expert eye pathologists for independent scoring. In total, 105 cases from 97 patients were evaluated. The initial consensus diagnoses using the WHO-EYE04 C-MIL system were as follows: 28 benign conjunctival melanoses, 13 low-grade C-MIL, 37 high-grade C-MIL, and 27 conjunctival MIS. Using this system resulted in 93% of the pathologists showing only fair-to-moderate agreement (kappa statistic) with the consensus score. The WHO-EYE05 C-MIL system (with high-grade C-MIL and MIS combined) improved consistency between pathologists, with the greatest level of agreement being seen with benign melanosis (74.5%) and high-grade C-MIL (85.4%). Lowest agreements remained between pathologists for low-grade C-MIL (38.7%). Regarding WHO-EYE05 C-MIL scoring and clinical outcomes, local recurrences of noninvasive lesions developed in 8% and 34% of the low- and high-grade cases. Invasive melanoma only occurred in 47% of the cases that were assessed as high-grade C-MIL. This extensive international collaborative study is the first to undertake a comprehensive review of the WHO-EYE05 C-MIL scoring system, which showed good interobserver agreement and reproducibility.

Characterisation of the protein expression of the emerging immunotherapy targets VISTA, LAG-3 and PRAME in primary uveal melanoma: insights from a southern French patient cohort

Uveal melanoma (UM) is the most common intraocular tumour in adults, with dismal prognosis once metastases develop, since therapeutic options for the metastatic disease are ineffective. Over the past decade, novel cancer therapies based on immunotherapy have changed the landscape of treatment of different forms of cancer leading to many hopes of improvement in patient overall survival (OS). VISTA, LAG-3 and PRAME are novel promising targets of immunotherapy that have recently gained attention in different solid tumours, but whose relevance in UM remained to be comprehensively evaluated until now. Here, we studied the protein expression of VISTA, LAG-3 and PRAME using immunohistochemistry in representative whole tissue sections from primary UM cases in a cohort of 30 patients from a single centre (Nice University Hospital, Nice, France). The expression of each of these markers was correlated with different clinical and pathological parameters, including onset of metastases and OS. We demonstrated the protein expression of VISTA and LAG-3 in small lymphocytes infiltrating the tumour, while no expression of the proteins was detected in UM cells. For PRAME, nuclear expression was observed in UM cells, but no expression in tumour infiltrating immune cells was identified. Increased levels of VISTA expression in tumour infiltrating lymphocytes (TILs) were associated with nuclear BAP1 expression and better prognosis. Higher levels of LAG-3 in TILs were associated with higher levels of CD8-positive TILs. PRAME nuclear positivity in melanoma cells was associated with epithelioid cell dominant (>90%) UM histological subtype, higher mitotic numbers and a higher percentage of chromosome 8q gain. This study proposes VISTA as a novel relevant immune checkpoint molecule in primary UM and contributes to confirm LAG-3 and PRAME as potentially important immunotherapy targets in the treatment of UM patients, helping to expand the number of immunotherapy candidate molecules that are relevant to modulate in this aggressive cancer.

Immunohistochemistry for PRAME in Dermatopathology

ABSTRACT

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.

PRAME expression in 137 primary cutaneous melanomas and comparison with 38 related metastases

Melanocytic lesions have always represented a diagnostic challenge for surgical pathologists. According to the literature, PRAME showed great promise as an immunohistochemical tool in the distinction between benign and malignant melanocytic lesions. In the present study, we retrospectively analyzed 137 thicker (Breslow > 1 mm) primary cutaneous melanomas with the aim to better understand the utility of PRAME immunohistochemistry in daily practice and also to investigate if PRAME could represent a prognostic biomarker for cutaneous melanomas. PRAME immunohistochemistry was performed in all melanomas and in the metastases with antibodies to PRAME (dilution 1:1000, clone Ab219650) on an automated immunostainer (Ventana Benchmark Ultra) using a brown chromogen (DAB). We found that melanomas (59.1%) show diffuse PRAME expression (score 4 +). 99 (72.3%) primary cutaneous melanoma had no relapse during the follow-up. Of this group of melanomas, 61/99 (61.6%) were diffusely positive for PRAME. 38 (27.7%) primary cutaneous melanoma had relapses. Of this group, 28/36 (77.7%) were diffusely positive. We did not find any statistical correlation between diffuse PRAME expression and the presence of driver mutation in BRAF gene (p = 0.927), NRAS gene (p = 0.496) or either of the two (p = 0.138). We did not find a prognostic significance of diffuse PRAME expression for relapse (p = 0.462) or survival rate (p = 0.245). The prognostic value of PRAME has been only reported in mucosal, uveal and cutaneous thin melanomas. Here, we show statistical analyses on PRAME expression for melanoma with Breslow > 1 mm based on survival rate and long-term follow-up. According to our results, PRAME is a useful immunohistochemical ancillary tool in daily practice diagnosis of melanocytic lesions.

PRAME/MELAN-A double immunostaining as a diagnostic tool for conjunctival melanocytic lesions: A South American experience

INTRODUCTION

PRAME (PReferentially expressed Antigen in Melanoma) is an antigen that is predominantly expressed in human melanomas. In cutaneous melanocytic lesions, PRAME expression is associated with malignancy. The objective of this study was to evaluate the co-expression of PRAME and Melan A to evaluate their diagnostic value in different conjunctival melanocytic lesions (CML).

METHODS

37 CML (23 nevi, 9 primary acquired melanosis (PAM), and 5 conjunctival melanomas) were evaluated by immunohistochemistry for PRAME and Melan-A. The percentage of melanocytic cells co-expressing PRAME and Melan-A was qualitatively evaluated as follows: negative, 0%; 1 + , 1-25%; 2 + , 26-50%; 3 + , 51-75% and 4 + , ≥ 76%.

RESULTS

Of the invasive melanoma cases, 80% showed a 4 + pattern of marking, whereas 20% showed a 3 + pattern. 11% of the PAMs showed a 4 + pattern and 88.9% showed a 1 + pattern. All the nevi showed a 1 + pattern. The sensitivity and specificity of PRAME 4 + for differentiating high-grade CML from the benign and low-grade grouped CML are 93% and 100%, respectively.

CONCLUSION

PRAME/MELAN-A double immunostain is particularly useful to differentiate benign from malignant conjunctival melanocytic lesions.

PRAME Expression in Mucosal Melanoma of the Head and Neck Region

PRAME (PReferentially expressed Antigen in MElanoma), a cancer-testis antigen expressed in normal and neoplastic tissues with several functions, proved to be a useful diagnostic tool in the differential diagnosis between benign and malignant melanocytic lesions. The current study aims to perform PRAME stain on a retrospective case series of mucosal melanocytic tumors of the head and neck region to compare 3 different scores and evaluate the most reliable one in this diagnostic set. Immunohistochemical analysis for PRAME was performed in 54 benign and malignant mucosal melanocytic tumors of the head and neck region collected from 41 patients. The best-performing cutoff of PRAME-positive cells (nuclear stain) to differentiate benign and malignant mucosal melanocytic tumors of the head and neck region is that proposed by Raghavan and colleagues (<60%/≥60% of PRAME-positive cells), with 100% and 77.8% of benign lesions and malignant tumors respectively correctly identified. Applying this score, PRAME stain showed the best results (sensitivity, specificity, accuracy, and positive and negative predictive values) for the diagnosis of head and neck melanocytic tumors. However, a subset of PRAME-negative malignant tumors was identified, especially located in the palatal area (hard and soft palate). Finally, high PRAME expression (≥60%) was associated with specific sites (nasal cavity/nasal septum/turbinates nasopharynx, and the maxillary sinus), nodular histotype, and female sex.

PRAME immunohistochemistry is useful in differentiating oral melanomas from nevi and melanotic macules

BACKGROUND

Oral melanocytic neoplasms pose a diagnostic challenge to pathologists owing to their rarity relative to those in the skin. The utility of PRAME in distinguishing nevi from melanomas has been established in the skin, but limited information exists regarding its usefulness in the oral cavity.

METHODS

Thirty-five previously diagnosed pigmented oral lesions were retrospectively evaluated with PRAME. The lesions consisted of 16 oral nevi, 10 melanomas, and 10 melanotic macules.

RESULTS

Strong and diffuse nuclear PRAME staining was observed in all but one of the oral melanomas, which showed no staining. No nuclear PRAME staining was observed in any of the oral nevi or melanotic macules.

CONCLUSIONS

PRAME is a useful tool in the evaluation of oral melanocytic neoplasms. Our data indicate that PRAME is a highly specific but incompletely sensitive marker of oral melanoma. Larger studies could further illuminate the diagnostic value of PRAME in oral lesions.

PRAME expression by immunohistochemistry and reverse transcription quantitative PCR in conjunctival melanocytic lesions-a comprehensive clinicopathologic study of 202 cases and correlation of cytogenetics with PRAME expression in challenging conjunctival melanocytic lesions

This study examined PRAME (preferentially expressed antigen in melanoma) expression by immunohistochemistry and reverse transcription quantitative PCR (RT-qPCR) in 202 histologically unequivocal conjunctival melanocytic lesions: 76 nevi, 29 benign melanoses, 25 low-grade conjunctival intraepithelial melanocytic lesions (LGCMIL), 26 high-grade conjunctival melanocytic intraepithelial lesions/in-situ melanoma (HGCMIL), and 46 invasive melanomas. PRAME score 0 was seen in 96% of nevi (73/76), 96% of benign melanoses (28/29), and 88% of LGCMIL (22/25). PRAME score 4 was seen in 50% HGCMIL (13/26) and 76% invasive melanomas (35/46). PRAME score 4 had a sensitivity of 50% and specificity of 100% in differentiating between HGCMIL and benign melanosis/LGCMIL. PRAME score 4 had a sensitivity of 76% and specificity of 100% in differentiating between melanoma and nevi. Relative quantification of PRAME mRNA expression by RT-qPCR was performed on 49 cases (24%): 17 nevi, 3 benign melanoses, 5 LGCMIL, 9 HGCMIL, and 15 invasive melanomas. The analysis generated two distinct groupings with 'high' relative PRAME expression for the HGCMIL and invasive melanoma and 'low/zero' expression for nevi, benign melanosis, and LGCMIL. Thirty-three challenging conjunctival melanocytic lesions that had previous fluorescence in situ hybridization (FISH) analysis were studied: 18 nevi, 12 melanomas in a nevus, 2 nevoid melanomas, and 1 in-situ melanoma. All nevi (100%) showed concordance between negative FISH and PRAME (scores 0-3). Four of 13 melanomas (31%; in-situ, invasive, isolated, and in association with nevus) showed concordance between positive FISH and PRAME score 4. In conclusion, PRAME score 4 has 100% specificity for the diagnosis of HGCMIL and melanoma. PRAME is limited in its sensitivity in the evaluation of challenging melanocytic lesions.

PRAME is a useful marker for the differential diagnosis of melanocytic tumours and histological mimics

AIMS

Although the morphological assessment of melanoma is generally straightforward, diagnosis can be especially difficult when the significant morphological and immunohistochemical results overlap with those of benign and malignant melanocytic tumours and histological mimics. This study assessed the potential diagnostic utility of measuring PReferentially expressed Antigen in MElanoma (PRAME) immunohistochemically in naevi, melanomas and clear cell sarcomas (CCSs) in Chinese patients.

METHODS

We examined the immunohistochemical expression of PRAME in 317 melanocytic naevi, 178 primary melanomas, 72 metastatic melanomas and 19 CCSs and compared the sensitivity and specificity of PRAME immunohistochemistry (IHC) in the differential diagnosis of melanocytic tumours and histological mimics.

RESULTS

Of the 317 melanocytic naevi, 98.1%were completely negative for PRAME; six cases showed focal PRAME immunoreactivity in a minor population of lesional melanocytes. Diffuse nuclear immunoreactivity for PRAME was found in 89.9% of primary melanomas and 93.1% of metastatic melanomas. Regarding melanoma subtypes, PRAME was expressed in 100% of superficial spreading melanomas, 100% of melanomas arise in congenital naevus, 91.4% of nodular melanomas, 87.8% of acral lentigo melanomas, 80.0% of lentigo malignant melanomas, 60.0% of Spitz melanomas, 96.2% of mucosal melanomas and 80.0% of uveal melanomas. None of the two desmoplastic melanomas expressed PRAME. Of the 19 CCS cases, 89.5% were negative for PRAME and 10.5% showed focal weak PRAME immunoreactivity in a minor population of tumour cells.

CONCLUSIONS

Our findings indicate that PRAME may be a useful marker to support a suspected diagnosis of melanoma. In addition, lack of PRAME expression is a valuable hint to CCS in a suspected case, and then molecular confirmation of the presence of EWSR1 rearrangement is necessary.

PRAME Immunohistochemistry of Spitzoid Neoplasms

BACKGROUND

Spitzoid melanocytic neoplasms are well known to be diagnostically challenging. Immunohistochemistry and molecular approaches have been used as ancillary diagnostic tests. Herein we investigate the use of PRAME immunohistochemistry (IHC) for the assessment of spitzoid melanocytic neoplasms.

METHODS

10 Spitz nevi, 14 atypical Spitz tumors, and 11 spitzoid melanomas were retrieved and PRAME IHC was scored on a scale of 1-4 (in % quartiles). Intensity of staining was categorized as weak or strong. Cases with no staining received a score of 0. Positive lymph nodes from three spitzoid melanomas were also analyzed.

RESULTS

Spitz nevi, atypical Spitz tumors, and spitzoid melanomas had mean PRAME IHC scores of 1.20, 0.93, and 3.36 respectively. The percentage of cases with a score 3 or higher for each category of spitzoid neoplasms are as follows: Spitz nevus (20%), atypical Spitz tumor (0%), and spitzoid melanoma (82%). Among the spitzoid melanomas, 3 cases had positive sentinel lymph nodes which demonstrated PRAME score of 2, 4, and 4 in the metastatic deposits.

CONCLUSIONS

Previous reports revealed PRAME IHC as useful to distinguish benign from malignant melanocytic lesions. The results presented here are concordant with the prior studies, but expand the application of this marker to Spitz nevi/tumors and spitzoid melanomas. The present findings suggest the potential diagnostic utility of PRAME IHC in the assessment of spitzoid melanocytic lesions, particularly in distinguishing spitzoid melanomas from Spitz nevi and atypical Spitz tumors. This article is protected by copyright. All rights reserved.

PRAME Expression in Junctional Melanocytic Proliferations of the Conjunctiva: A Potential Biomarker for Primary Acquired Melanosis/Conjunctival Melanocytic Intraepithelial Lesions

ABSTRACT

Conjunctival melanocytic proliferations are diagnostically challenging, often complicated by small specimen size, and are separated into 3 broad categories. The first group includes benign nevi and primary acquired melanosis (PAM) without atypia. The second group includes junctional melanocytic proliferations with a risk of progression to invasive melanoma (PAM with atypia). The last category is conjunctival melanoma, of which 65% of tumors arise in the setting of PAM with atypia. Preferentially expressed antigen in melanoma (PRAME) immunohistochemistry has been widely adopted to differentiate cutaneous nevi and melanoma. However, there are limited studies on its utility in the evaluation of conjunctival melanocytic proliferations with little data regarding its potential utility in stratifying PAM. Twenty-eight clinically annotated cases (14 PAM without atypia and 14 PAM with atypia) were retrospectively evaluated with PRAME/MART-1 duplex immunohistochemistry and were assigned the commonly used PRAME immunoreactivity score: 0 for no staining, 1+ for 1%-25% of cells positive, 2+ for 26%-50%, 3+ for 51%-75%, and 4+ for >75%. PAM without atypia showed low (0-3+) PRAME expression in 14 of 14 cases (100%). PAM with atypia showed strong and diffuse (4+) PRAME expression in 12 of 14 cases (86.7%). Seven of eight (87.5%) PAM with severe atypia, 4 of 4 PAM (100%) with moderate atypia, and 1 of 2 PAM (50%) with mild atypia showed 4+ PRAME expression. In addition, all 5 cases that recurred or progressed (all classified as PAM with atypia) showed 4+ PRAME expression. Although additional larger studies are needed, PRAME seems to be a useful adjunct in evaluating junctional melanocytic proliferations of the conjunctiva.

Preferentially Expressed Antigen in Melanoma (PRAME) and Human Malignant Melanoma: A Retrospective Study

BACKGROUND

Preferentially expressed antigen in melanoma (PRAME) is a cancer testis antigen (CTA) identified in 1997 through analysis of the specificity of tumor-reactive T-cell clones derived from a patient with metastatic cutaneous melanoma. Although at first it seemed even more specific, various studies have shown that PRAME can also be expressed in the context of atypical lesions that do not correspond solely to the definition of malignant melanoma.

METHODS

A systematic review of English articles was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

126 records were identified in the literature search, of which 9 were duplicates. After screening for eligibility and inclusion criteria, 53 publications were included.

CONCLUSIONS

The advent of a new marker such as PRAME is surely a step forward not only in the diagnostic approach, but also in the immunotherapeutic approach to MM. However, various studies have shown that PRAME can also be expressed in the context of atypical lesions apart from MM and, for this reason, the diagnostic sensitivity and specificity (hence accuracy) are clearly lower. Further studies with larger case series will be necessary to understand better what possibilities are offered in terms of diagnostic reliability by PRAME.

Preferentially expressed antigen in melanoma immunohistochemistry as an adjunct for differential diagnosis in acral lentiginous melanoma and acral nevi

Preferentially expressed antigen in melanoma (PRAME) has shown promising utility in distinguishing benign melanocytic lesions from melanomas, but knowledge of its expression pattern in acral lentiginous melanoma (ALM) and acral nevi (ANs) is limited. Immunohistochemical expression of PRAME was examined in 75 ALMs and 34 ANs. The clinical and histopathologic characteristics of patients with ALM were collected. PRAME was immunoreactive in 89.3% (67/75) of ALMs, but entirely negative in 94.1% (32/34) of ANs. When staining at least 50% of lesional melanocytes was determined as positivity, the sensitivity and specificity of PRAME for distinguishing ALM from ANs were 69.3% and 100%, respectively. Seventy-one cases of ALMs had tumor cells in the epidermis; 71.8% (51/71) of them showed positive for PRAME. By contrast, 61 ALMs had tumor cells in the dermis; 65.6% (40/61) exhibited positive expression. Twenty-nine of 39 (74.4%) epithelioid cell ALMs were observed to be positive for PRAME. By comparison, 63.8% (23/36) of ALMs with spindle tumor cells were positive for PRAME. However, PRAME positive expression was not associated with any clinical and histopathologic characteristics of patients with ALM, including Breslow thickness, ulcer, cytomorphology, lymph node metastasis, or tumor-infiltrated lymphocytes (TILs). Nevertheless, we observed that 82.6% (19/23) of ALMs with lymph node involvement at diagnosis expressed PRAME, compared with 57.6% (20/35) of those without. In summary, PRAME immunohistochemistry can serve as a helpful adjunct in the differential diagnosis of ALMs and ANs with good sensitivity and high specificity. Additionally, PRAME tends to have a higher positive rate in epidermal melanocytes than in the dermis and is inclined to express in epithelioid cells than in spindle cells of ALMs.

PRAME expression in melanocytic lesions of the conjunctiva

AIMS

PRAME (PReferentially expressed Antigen in MElanoma) is a tumour-associated antigen that is preferentially strongly expressed in most cutaneous melanomas but not or only focally in nevi. Our aim was to evaluate PRAME expression in melanocytic lesions of the conjunctiva.

METHODS AND RESULTS

Surgical specimens of 114 conjunctival melanocytic nevi of different types (including 67 common, 25 combined deep penetrating and 21 inflamed juvenile nevi), 30 invasive melanomas, 10 in situ melanomas, 23 primary acquired melanoses (PAM) without atypia and 11 PAM with atypia were analysed for PRAME expression by immunohistochemistry. Nuclear positivity for PRAME in melanocytes was assessed as the percentage of positive nuclei: negative (0%), 1+ (1-25%), 2+ (26-50%), 3+ (51-75%) and 4+ (>75%). In 113 of 114 conjunctival melanocytic nevi, PRAME was either completely negative or focally 1+ positive. Diffuse 4+ PRAME expression was identified in 17 of 30 (57%) invasive melanomas, 7 of 10 (70%) in situ melanomas, 4 of 5 (80%) PAM with severe atypia, 0 of 3 PAM with moderate atypia, 0 od 3 PAM with mild atypia, 1 of 23 (4%) PAM without atypia and 0 of 114 nevi. Diffuse 4+ PRAME expression in invasive melanomas correlated with a higher mitotic count but was not related to age and gender of the patients, Breslow thickness, location or mutational status.

CONCLUSION

Diffuse 4+ PRAME positivity is highly specific for malignant conjunctival melanocytic lesions. PRAME is therefore a useful ancillary marker to support the diagnosis of a suspected conjunctival melanoma.