Molecular alterations in malignant blue nevi and related blue lesions

Spectrum of blue nevus-like lesions, including blue nevus, pigmented epithelioid melanocytoma, and animal-type melanoma

Blue nevus-like lesions constitute a category of melanocytic lesions that are clinically identified by their blue coloration. Histologically, they exhibit two primary features: a dermal location and intense pigmentation. The latest World Health Organization classification categorizes blue melanocytic lesions into benign entities (dermal melanocytoses, blue nevus, and deep penetrating nevus), melanocytic tumors with low-to-intermediate malignant potential (pigmented epithelioid melanocytoma), and malignant lesions (blue nevus-like melanoma and melanoma arising in blue nevi). Clinically, blue nevi are enduring and stable lesions, displaying a structureless blue pigmentation clinically and dermatoscopically, with a straightforward histologic diagnosis. On the contrary, lesions with recent onset and/or rapid growth are more commonly associated with diagnoses falling within the intermediate part of the spectrum or with melanoma. These lesions often present with a blue color along with additional features such as black blotches, irregular vessels, and irregular pigmented globules. They typically emerge de novo without recognizable precursors, and they pose significant challenges for patient management. Melanoma on a blue nevus is an exceedingly rare entity with only a few cases described to date. Histologically, differentiating between lesions with intermediate malignant potential and melanoma is always challenging, necessitating a comprehensive evaluation of all morphologic findings of the lesion.

Melanocytic lesions with blue naevus-like (dendritic) morphology: an update with an emphasis on histopathological, immunophenotypic, and molecular features

An accurate diagnosis of melanocytic lesions requires a thorough histopathological evaluation accompanied by appropriate correlation with clinical examination findings. Although most melanocytic lesions can readily be classified as one of the defined diagnostic entities according to well-established diagnostic criteria, a subset of melanocytic lesions, particularly those with blue naevus-like (pigmented dendritic) morphology, have notoriously constituted an enduring challenge for pathologists. These lesions are rare and often show histological ambiguities, with features of both benignity and malignancy, thereby making accurate risk assessment and prediction of their biological behaviours difficult on histological grounds alone. Herein, we outline a practical and systematic approach for the diagnosis of melanocytic lesions with dendritic morphology, with a particular focus on histological and immunophenotypic features that help to distinguish one entity from another. In this review, we provide the most current knowledge on these melanocytic lesions in the literature and our experience with these rare entities, and we discuss the utility of molecular techniques as an ancillary tool, especially in histologically ambiguous and/or borderline lesions.

KRAS, BRAF, PIK3CA mutation frequency of radical prostatectomy samples and review of the literature

OBJECTIVE

The molecular basis of prostate cancer is highly heterogeneous. Our study aimed to perform the mutation analysis of KRAS, BRAF, PIK3CA, and immunohistochemical (IHC) evaluation of EGFR, HER2, p16, and PTEN to demonstrate new areas for targeted therapies.

METHODS

A total of 24 prostatectomy samples diagnosed with adenocarcinoma were analyzed by microarray hybridization. Also, these samples were IHC stained for EGFR, HER2, P16, and PTEN. The cases were divided into two groups based on low and high Gleason scores. All findings were compared with the clinicopathological parameters of the patients.

RESULTS

While KRAS mutation was in 3/24 (12.5%) of our cases, BRAF and PIK3CA mutations were not detected. There was no significant difference between the groups in terms of KRAS mutation frequency. HER2 was immunohistochemically negative in all samples. There was no correlation between EGFR, P16 immunopositivity, and clinicopathological features.

CONCLUSION

KRAS mutation frequency is similar to those in Asian populations. BRAF and PIK3CA mutation frequencies have been reported in the literature in the range of 0-15% and 0-10.4%, respectively, consistent with our study findings. HER2 immunoexpression is a controversial issue in the literature. EGFR and p16 expressions may not correlate with the stage.

BRAF mutation, TERT promoter mutation, and HER2 amplification in sporadic or neurofibromatosis-related neurofibromas and malignant peripheral nerve sheath tumors: do these molecules have a signature in malignant transformation?

Peripheral nerve sheath tumors may occur sporadically or related to neurofibromatosis (NF). Unless the mechanisms of tumorigenesis in NF related malignant peripheral nerve sheath tumors (MPNST) are better understood, it remained unclear in sporadic cases. We aimed to investigate the genetic route for malignancy in both individuals with NF-1 and sporadic ones to open a way for targeted therapies in the future. We investigated the role of HER2 with Dual ISH DNA Probe Cocktail test, BRAF mutation (exon 15) and TERT promoter mutation frequency with Sanger sequencing method in respectively 25 sporadic neurofibromas, 25 NF-1 related neurofibromas and 25 MPNST cases from two institutes. Categorical data were analyzed and summarized as frequency and percentage. Statistical analysis was done with SPSS v.22 statistical package, and the statistical significance level was considered as 0.05. We identified TERT promoter mutation only in one sporadic MPNST (4%) and no BRAF mutation in any case. HER2 amplification is found in 10/25 (40%) MPNST cases. No mutations or gene amplification detected in neurofibromas (p < 0.001). MPNSTs are sarcomas with poor prognosis and limited treatment options. TERT promoter mutations and HER2 amplification may play a putative role in therapeutic purposes.

The color of skin: black diseases of the skin, nails, and mucosa

Gradations in skin color are a consequence of differing amounts of melanin and their varying distribution. Although many darkly pigmented skin lesions are melanocytic and can be attributed to melanin content, the color of a black lesion can also be due to blood, necrotic tissue, or exogenous pigment. The source, pattern, and distribution of the color in black lesions usually offer important insight into its etiology. This contribution reviews conditions that can take on a black color, discussing the cause of the hue and any additional impact sun exposure may have.

Unusual melanoma of the scalp with blue nevus-like features and local metastasis: A case report

We present an unusual case of melanoma in a 76-year-old female covering approximately 80% of her scalp. Partial sampling of the lesion revealed focal blue nevus-like features at the microscopic level. We discuss issues related to blue nevus-like melanomas and highlight the unique clinical presentation of the current case.

Genetic profile of GNAQ-mutated blue melanocytic neoplasms reveals mutations in genes linked to genomic instability and the PI3K pathway

Melanomas arising in association with a common or cellular blue nevus (MABN) comprise a relatively rare and heterogeneous group of lethal melanomas. Although GNAQ is known to be frequently mutated in common blue nevus, cellular blue nevus (CBN) and MABN and these malignant lesions present gross chromosome alterations harboring BAP1 mutations, little is known about other mutations that contribute to the development and progression of these neoplasms. Thus, the genetic profile of these tumors is important to increase the number of intervention and treatment modalities. Here, we characterized and genetically profiled two different sections of a rare MABN and two CBNs from three different patients. All of the samples harbored a GNAQ mutation, exhibited RAS pathway activation, and harbored additional mutations in genes associated with genomic instability and epigenetic regulation (KMT2C, FANCD2, ATR, ATRX, NBN, ERCC2, SETD2, and WHSC1). In addition, all neoplasms harbored mutations that directly or indirectly affected either the regulation or activation of the PI3K pathway (PIK3CA, NF1, INPP5B and GSK3B). Our results not only help understand the genetic complexity of these blue melanocytic lesions but provide a rationale to use the combination of PI3K/MTOR and MEK1/2 inhibitors against these types of tumors.

Genomic Assessment of Blitz Nevi Suggests Classification as a Subset of Blue Nevus Rather Than Spitz Nevus: Clinical, Histopathologic, and Molecular Analysis of 18 Cases

Blitz nevi/tumors are a distinct subset of melanocytic neoplasia which show mixed morphologic features of Spitz and blue nevus. Genomically, most blue nevi have GNAQ or GNA11 mutations while most Spitzoid neoplasms have either an HRAS mutation or translocations involving MET, ROS, BRAF, ALK1, NTRK1, and RET. The criteria used for the assessment of malignancy in blue and Spitzoid lesions are different, and these lesions have different prognostic markers. In this study, we assess the clinical, morphological, and genomic changes in 18 cases of Blitz nevi/tumors to better characterize this subset of neoplasms and determine their optimal genomic classification. Most lesions occurred on the extremities followed by the head and neck region typical of blue nevi. Histology showed most cases having a prominent plexiform growth pattern with cells aggregating around the adnexal structures and neurovascular bundles also typical of blue nevi. Using next generation sequencing, we detected the presence of somatic mutations in GNAQ or GNA11 in 4 of 7 cases (57%) of Blitz nevi with sufficient DNA available for sequencing. Normal skin samples in these 4 cases were sequenced to confirm that the GNAQ or GNA11 mutations were somatic mutations. All 4 cases were negative for immunohistochemical assessment for wild-type BRAF, RET, ALK, and NTRK1 and mutational analysis of HRAS was also negative in all cases. Hence, our study suggests that Blitz nevi/tumors are a distinct subset which genomically are best classified as a subset of blue nevi.

Cellular Blue Nevus Diagnosed following Excision of Melanoma: A Challenge in Diagnosis

A case of a 41-year-old woman with a history of nodular melanoma (NM), associated with an indurated dome-shaped blue-black nodule with a diameter of 1.2 cm in the gluteal region, is presented. Clinical diagnosis of the lesion, present from birth, was blue nevus. Recently, the nodule has been showing a mild enlargement and thus complete resection was performed. Histological analysis revealed a pigmented lesion with an expansive pattern of extension into the dermis and the subcutaneous adipose tissue. The lesion displayed an alveolar pattern as well as a pigmented dendritic cell pattern. The histology was consistent with cellular blue nevus (CBN); however, the history of NM which was excised one year earlier, as well as the clinical information about the slow growing lesion, included a differential diagnosis of CBN, borderline melanocytic tumor, and malignant blue nevus. Additional immunohistochemical (HMB-45, p16, and Ki-67) and molecular (BRAF V600E mutation) analyses were performed on both lesions: the CBN-like and the previously excised NM. Along with lesion history and histological analyses, p16 staining and BRAF were useful diagnostic tools for confirming the benign nature of CBN in this case.