Nevoid melanoma: A study of 43 cases with emphasis on growth pattern

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.

Dermoscopic features of nevoid melanoma: a retrospective study

BACKGROUND

Nevoid melanoma (NeM) is a rare variant of melanoma resembling melanocytic nevus. The aim of the study was to systematically review the dermoscopic features of NeM.

METHODS

A hospital-based retrospective study was conducted. Dermoscopic features of NeMs diagnosed through excisional biopsy between January 2015 1, and March 1, 2021, were compared to superficial spreading melanomas (SSMs) matched by Breslow's thickness. Then, a literature search was performed. Electronic searches on PubMed database via Medline were conducted to retrieve any manuscript reporting detailed dermoscopic features of histopathologically confirmed NeM.

RESULTS

A total of 60 malignant melanomas (MM) comprising 20 NeM and 40 SSM were collected. Twelve out of 20 (60%) NeM showed a nevus-like appearance, including reticular and globular patterns, and in 35% of these cases it was detected because of dermoscopic changes. Then, a total of seven original manuscripts were retrieved from the literature review, comprising 56 cases overall. NeM showed nevus-like pattern in 53% of the cases, multicomponent pattern in 21% and amelanotic in 9%. Enlargement, irregularly distributed dots/globules, irregular pigmentation, and atypical vascular pattern were found in NeM with nevus-like appearance. NeM with multicomponent pattern were characterized by irregular pigmentation, blue-white veil, irregular dots and atypical vascular pattern. Amelanotic NeM is rare and show atypical vascular pattern and milia-like cysts.

CONCLUSIONS

Dermoscopy of NeM is challenging as it frequently shows a nevus-like pattern, but clues and detection of dermoscopic changes may help to identify it.

Cutaneous Melanomas Arising during Childhood: An Overview of the Main Entities

Cutaneous melanomas are exceptional in children and represent a variety of clinical situations, each with a different prognosis. In congenital nevi, the risk of transformation is correlated with the size of the nevus. The most frequent type is lateral transformation, extremely rare before puberty, reminiscent of a superficial spreading melanoma (SSM) ex-nevus. Deep nodular transformation is much rarer, can occur before puberty, and must be distinguished from benign proliferative nodules. Superficial spreading melanoma can also arise within small nevi, which were not visible at birth, usually after puberty, and can reveal a cancer predisposition syndrome (CDKN2A or CDK4 germline mutations). Prognosis is correlated with classical histoprognostic features (mainly Breslow thickness). Spitz tumors are frequent in adolescents and encompass benign (Spitz nevus), intermediate (atypical Spitz tumor), and malignant forms (malignant Spitz tumor). The whole spectrum is characterized by specific morphology with spindled and epithelioid cells, genetic features, and an overall favorable outcome even if a regional lymph node is involved. Nevoid melanomas are rare and difficult to diagnose clinically and histologically. They can arise in late adolescence. Their prognosis is currently not very well ascertained. A small group of melanomas remains unclassified after histological and molecular assessment.

Mitotically Active Nevus and Nevoid Melanoma: A Clinicopathological and Molecular Study

ABSTRACT

The distinction between nevoid melanoma and a mitotically active nevus can be challenging at the microscopic level. In this study, we performed cytogenetic testing on a cohort of 25 mitotically active melanocytic proliferations resembling common melanocytic nevus from 25 patients. Based on cytogenetic findings, the lesions were classified as "nevoid melanoma" (n = 13) or "mitotically active nevus" (n = 12). Subsequently, we compared the clinicopathological features between these 2 groups. Nevoid melanomas occurred in older patients (P = 0.007); however, there were no significant differences in gender, size, or anatomical distribution between the 2 groups. Histologically, deep/marginal mitoses (P = 0.006), lack of maturation with depth (P = 0.036), and pseudo-maturation (P = 0.006) were significantly more common in nevoid melanomas. Immunohistochemically, complete loss of p16 was an important divisive feature (P = 0.0004), seen in 70% of nevoid melanomas, and highly correlated with loss of CDKN2A gene (chromosome 9p21). Our findings suggest that such reproducible immunomorphological differences can be of value in distinguishing nevoid melanoma from mitotically active nevus. Nevoid melanomas demonstrated a spectrum of chromosomal aberrations similar to those seen in common subtypes of melanoma, which can serve as a powerful adjunct diagnostic tool in morphologically challenging lesions.

Optimization of an automated tumor-infiltrating lymphocyte algorithm for improved prognostication in primary melanoma

Tumor-infiltrating lymphocytes (TIL) have potential prognostic value in melanoma and have been considered for inclusion in the American Joint Committee on Cancer (AJCC) staging criteria. However, interobserver discordance continues to prevent the adoption of TIL into clinical practice. Computational image analysis offers a solution to this obstacle, representing a methodological approach for reproducibly counting TIL. We sought to evaluate the ability of a TIL-quantifying machine learning algorithm to predict survival in primary melanoma. Digitized hematoxylin and eosin (H&E) slides from prospectively enrolled patients in the NYU melanoma database were scored for % TIL using machine learning and manually graded by pathologists using Clark's model. We evaluated the association of % TIL with recurrence-free survival (RFS) and overall survival (OS) using Cox proportional hazards modeling and concordance indices. Discordance between algorithmic and manual TIL quantification was assessed with McNemar's test and visually by an attending dermatopathologist. In total, 453 primary melanoma patients were scored using machine learning. Automated % TIL scoring significantly differentiated survival using an estimated cutoff of 16.6% TIL (log-rank P < 0.001 for RFS; P = 0.002 for OS). % TIL was associated with significantly longer RFS (adjusted HR = 0.92 [0.84-1.00] per 10% increase in % TIL) and OS (adjusted HR = 0.90 [0.83-0.99] per 10% increase in % TIL). In comparison, a subset of the cohort (n = 240) was graded for TIL by melanoma pathologists. However, TIL did not associate with RFS between groups (P > 0.05) when categorized as brisk, nonbrisk, or absent. A standardized and automated % TIL scoring algorithm can improve the prognostic impact of TIL. Incorporation of quantitative TIL scoring into the AJCC staging criteria should be considered.

Targeted next generation sequencing (NGS) to classify melanocytic neoplasms

This study piloted a pan-solid-tumor next generation sequence (NGS)-based laboratory developed test as a diagnostic aid in melanocytic tumors. 31 cases (4 "epithelioid" nevi, 5 blue nevi variants, 7 Spitz tumors [3 benign and 4 malignant] and 15 melanomas) were evaluated. All tumors [median diameter 7 mm (range 4-15 mm); median thickness 2.25 mm (range 0.25-12 mm)] yielded satisfactory results. The number of small nucleotide variants/tumor was significantly different between melanoma (median 18/tumor, range 4-71) and all other lesions (median 8/tumor, range 3-17) (P < 0.004) and malignant (median 16/tumor, range 4-71) vs benign lesions (median 7/tumor, range 3-14) (P = 0.01). BRAF, MET, NTRK1, and ROS fusions only occurred in benign Spitz tumors; EML4 fusion, BRAF, MAP2K1 and TERT mutations occurred in malignant Spitz tumors and/or melanoma. Amplifications and NRAS and NF1 mutations only occurred in melanoma. Most melanomas contained >1 pathogenic alteration. Developed NGS-based criteria correctly classified all malignant lesions in this series. 10/12 cases showed concordance with FISH; consensus diagnosis agreed with NGS classification in FISH-non-concordant cases. This pilot study suggests that NGS may be an effective diagnostic adjunct comparable to FISH, but further studies with larger numbers of cases are needed.

"Puffy shirt appearance": Cell crowding at low magnification may represent nevoid melanoma

BACKGROUND

Melanoma, particularly nevoid melanoma, can masquerade as benign. Helpful differentiating features include nuclear pleomorphism, atypia, prominent nucleoli, absent maturation, and increased mitotic figures. These can be subtle and easily missed unless carefully sought. Thus, the "puffy shirt appearance" concept was born from a Seinfeld episode in which the namesake character unintentionally agreed to wear a pirate-like puffy shirt. Consequently, he found himself out of place, sporting an outfit with "too much shirt in too little space". Similarly, at low-power, nevoid melanoma appears to have "too many cells in too little space". This is more pronounced and easier to appreciate when there is an associated nevus, where crowded, subtly malignant melanocytes stand out from the evenly distributed, more spaced out benign melanocytes.

METHODS

Twelve practicing dermatopathologists familiar with the puffy shirt concept in the context of melanoma were surveyed.

RESULTS

Hundred percent of participants found it most helpful as a triaging tool, prompting additional work up including higher magnification evaluation, additional levels, consultation, and/or immunohistochemistry.

CONCLUSIONS

The crowded cells in the "puffy shirt appearance" catch the eye and should provoke a more thorough inspection of the lesion. This sign is not pathognomonic for melanoma, but prompts more careful evaluation and helps prevent misdiagnosis.

Uncommon Histopathological Variants of Malignant Melanoma. Part 2

Despite new horizons opened by recent advances in molecular pathology, histological evaluation still remains the diagnostic gold standard regarding cutaneous melanocytic neoplasms. Several histological variants of melanoma have been described, and their knowledge is crucial for accurate diagnosis and classification of cases with unusual clinico-pathological features. Uncommon histological variants of melanoma have been described based on a broad constellation of features, including architectural pattern, stromal alterations, cytological attributes, and other morphological properties. This review is aimed at providing an extensive discussion of unusual but distinctive histopathological variants of melanoma.

Clinicopathologically problematic melanocytic tumors: a case-based review

Background

In spite of recent advances in the histopathological and molecular diagnosis of melanocytic neoplasms, a certain proportion of these lesions remain a daunting challenge for both the clinician and the pathologist.

Objectives

To emphasize the importance of close collaboration between clinicians and pathologists in case of problematic melanocytic lesions.

Patients

We report and discuss 5 problematic scenarios of melanocytic lesions, including tumoral melanosis, nevoid melanoma, lentiginous melanoma, spitzoid melanoma and BAPoma that may pose diagnostic difficulties in our practice.

Conclusions

Clinico-dermoscopic-pathological correlation, with incorporation of all the available data, in problematic melanocytic skin neoplasms is of paramount importance for accurate diagnosis.