Combined activation of MAP kinase pathway and ß-catenin signaling cause deep penetrating nevi.

Deep penetrating nevus (DPN) is characterized by enlarged, pigmented melanocytes that extend through the dermis. DPN can be difficult to distinguish from melanoma but rarely displays aggressive biological behavior. Here, we identify a combination of mutations of the ß-catenin and mitogen-activated protein kinase pathways as characteristic of DPN. Mutations of the ß-catenin pathway change the phenotype of a common nevus with BRAF mutation into that of DPN, with increased pigmentation, cell volume and nuclear cyclin D1 levels. Our results suggest that constitutive ß-catenin pathway activation promotes tumorigenesis by overriding dependencies on the microenvironment that constrain proliferation of common nevi. In melanoma that arose from DPN we find additional oncogenic alterations. We identify DPN as an intermediate stage in the step-wise progression from nevus to melanoma. In summary, we delineate specific genetic alterations and their sequential order, information that can assist in the diagnostic classification and grading of these distinctive neoplasms.Deep penetrating nevi (DPN) are unusual melanocytic neoplasms with unknown genetic drivers. Here the authors show that majority of DPN harbor activating mutations in the ß-catenin and the MAP-kinase pathways; this characteristic can help in the classification and grading of these distinctive neoplasms.

Occurrence of BAP1 germline mutations in cutaneous melanocytic tumors with loss of BAP1-expression: A pilot study.

Melanocytic BAP1-associated intradermal tumors (MBAITs) can either be sporadic or associated with a cancer-predisposition syndrome. In this study we explored the clinical status of 136 patients in which at least one MBAIT was found. 49/136 (36%) of them gave their signed consent for an oncogenetic BAP1 blood test. 28/136 patients (20%) diagnosed with an MBAIT had other MBAITs and/or a personal or familial history of BAP1-related cancers that could clinically designate them as potential carriers of a BAP1 germline mutation. 17 of these 28 patients underwent oncogenetic testing. A deleterious mutation of BAP1 was confirmed in 12/17 cases. 4/17 cases were wild-type; all had a single MBAIT and a history of skin melanoma. A variant of unknown significance was found in one case with multiple MBAITs. Among the 12 mutated cases, multiple MBAITs were present in 10/12 cases and were the only clinical sign in 4/12 cases. The remaining 32/49 blood-tested cases with an isolated MBAIT were wild type for BAP1 in 25/32 cases or showed a variant of unknown significance in 7/32 cases. We recommend, following the diagnosis of a MBAIT, performing a BAP1 immunohistochemistry in all other cutaneous melanocytic tumors removed previously or simultaneously and all skin melanomas. This screening could help clinicians prioritize which patients would most benefit from oncogenetic testing.

NRAS-mutated melanocytic BAP1-associated intradermal tumor (MBAIT): a case report.

Melanocytic BAP1-associated intradermal tumors (MBAITs) are epithelioid spitzoid looking, mostly intradermally located melanocytic tumors that often have tumor-infiltrating lymphocytes and a common nevus component. They occur sporadically but also in the context of an underlying BAP1 germline mutation. Recognition of these lesions is important because they can be a marker for an underlying BAP1-associated cancer syndrome. Most cases reported in the literature thus far were found to have both a BRAF and BAP1 mutation. Here, we report an unusual case of an MBAIT lesion with a combined NRAS and BAP1 mutation. A BAP1 germline mutation was excluded. Our case is the second case reported until now with this combination of mutations in this subset of lesions. In the other reported NRAS-/BAP1-mutated MBAIT case, presence of a BAP1 germline mutation was not tested. Our case confirms that the mutational spectrum in MBAITs is broader than previously thought. Just as in the BRAF-mutated cases, it is likely that a subset might be associated with a BAP1 germline mutation. In case of suspicion of an MBAIT lesion based on histological examination, diagnostic work-up should include assessment of protein expression and/or mutation analysis of at least BRAF, NRAS, and BAP1. Work-up should not be limited to analyzing only BRAF protein expression or mutation, since NRAS-mutated MBAITs might be missed.

[Molecular genetic study of benign pigmented neoplasms by fluorescence in situ hybridization].

Twenty samples of benign pigmented neoplasms of the skin, including 9 intradermal nevi and 11 complex ones, were investigated. Fluorescence in situ hybridization was used to detect the copy number of the RREB1 (6p25), MYB (6q23), and CCND1 (11q13) genes. Analysis of the findings revealed no significant changes characteristic of melanoma in the nevi. However, the authors established that there was a direct correlation between the copy number of the MYB and RREB1 genes and that the amount of the MYB gene most frequently deviated from the normal values. In addition, a relationship was found between the number of MYB gene copies and the depth of the epidermal layer. In cases of an intradermal nevus, the copy numbers of the CCND1 and MYB genes were shown to vary more greatly than in cases of a complex nevus.

Fluorescence in situ hybridization for distinguishing nevoid melanomas from mitotically active nevi.

Nevoid melanoma may resemble benign compound or intradermal nevi by their silhouette and profile on low power. Higher power usually reveals nuclear atypia, confluence of cells, incomplete maturation and dermal mitotic activity. However, to some extent all of these features maybe seen in benign compound or intradermal nevi and no single criteria can be used to differentiate nevoid melanoma from a benign nevus. The distinction can be particularly problematic in nevi that show mitotic activity and we have noted a recent trend in diagnosis of melanocytic neoplasms with dermal mitosis as nevoid melanoma despite the presence of normal maturation in the dermis and lack of significant nuclear atypia. Therefore in this study we evaluated 10 nevoid melanomas, 4 of which resulted in metastasis and 10 mitotically active nevi with fluorescence in situ hybridization targeting key chromosomal loci previously shown to effectively discriminate been malignant and benign melanocytic neoplasms. All 10 nevoid melanomas showed copy number abnormalities by fluorescence in situ hybridization in either chromosome 6 or 11 while none of the 10 mitotically active nevi did. The results demonstrate that fluorescence in situ hybridization targeting key chromosomal loci on chromosomes 6 and 11 can be effective in discriminating nevoid melanomas from mitotically active nevi. Additionally, our study presents further evidence that dermal mitoses alone without other diagnostic features such as nuclear atypia and lack of maturation does not constitute sufficient evidence alone for a diagnosis of melanoma.

Aberrant DNA methylation silences the novel heat shock protein H11 in melanoma but not benign melanocytic lesions.

BACKGROUND: The heat shock protein H11 is silenced in melanoma cell lines, where its forced expression by demethylation with Aza-C triggers apoptosis. OBJECTIVE: To examine whether H11 is silenced by aberrant DNA methylation in melanoma as compared to nevi and normal skin tissues. METHODS: Cell suspensions from benign intradermal nevi, atypical nevi and malignant melanoma tissues were used in reverse-transcriptase PCR and methylation-specific PCR. Paraffin-embedded tissues were stained with H11 antibody. RESULTS: H11 is methylated in 60-75% of melanoma and atypical nevi, but not in normal skin or most benign nevi. Methylation is inversely correlated with H11 expression. CONCLUSION: The heat shock protein H11 is silenced by aberrant DNA methylation in melanoma, but not benign melanocytic lesions or normal skin melanocytes. The data suggest that H11 is a promising target for the molecular therapy of melanoma.

Linear psoriasis with porokeratotic eccrine ostial and dermal duct nevus.

Linear psoriasis is an uncommon form of psoriasis characterized by the linear distribution of the psoriatic lesions. It usually follows the lines of Blaschko with unilateral involvement. Poro keratotic eccrine ostial and dermal duct (PEODD) nevus is another rare dermatosis that follows Blaschko's line. The pathogenesis of linear psoriasis and PEODD nevus is unclear, but both could be best explained by a specific somatic mutation. Hence, it has been suggested that the mutation responsible for PEODD nevus would constitute a rare but critical psoriasis gene. In the literature, 1 case of linear psoriasis with PEODD nevus was reported, which may support this suggestion. This article describes another case of linear psoriasis and PEODD nevus. A 7-year-old boy had a 4-month history of multiple psoriasiform plaques, arranged in linear distribution, and had congenital linear hyperkeratotic papules and pits on the right side of his trunk and right arm.

Reduction of expression of tuberin, the tuberous-sclerosis-complex-gene-2 product in tuberous sclerosis complex associated connective tissue nevi and sporadic squamous and basal cell carcinomas.

BACKGROUND: Patients affected with tuberous sclerosis complex (TSC) are prone to the development of multiple benign tumors of the skin and other organs. Tuberin, the protein product of the tuberous-sclerosis-complex-2 tumor suppressor gene (TSC2) has been shown to inhibit cell proliferation. In TSC associated kidney tumors and sporadic brain tumors the loss/reduction of tuberin has been shown. METHODS: Specimens of nine squamous cell carcinomas (SCC) and five basal cell carcinomas (BCC) from patients without TSC and six biopsies of connective tissue nevi (CTN) of patients with TSC were obtained. Specimens were analyzed by immunoblotting for the expression of tuberin. RESULTS: Absent or reduced levels of tuberin were detected in the dermal parts of three of six shagreen patches, two of five BCC, and four of nine SCC. CONCLUSIONS: In tumors/hamartomas of patients with TSC the complete loss of TSC2 and tuberin is a mechanism which could be shown for CTN, thereby excluding the possibility of haploinsufficiency of TSC2. In a substantial number of cutaneous BCC and SCC the loss or downregulation of tuberin seems to be epigenetic, as alterations of TSC2 are not known in these tumors. The absence or reduction of tuberin might contribute to their proliferation.

DNA ploidy and nuclear morphometry for the classification of dysplastic nevi.

OBJECTIVE: To examine the diagnostic value of DNA ploidy and nuclear morphometric features in sporadic dysplastic nevi as compared to those in compound nevi and melanoma. STUDY DESIGN: DNA ploidy profiles plus seven direct and three derived nuclear features were obtained in a series of 120 melanocytic skin neoplasms (30 dysplastic nevi [DN], 30 melanomas [MM], 60 compound nevi [CN]) and the results compared. RESULTS: DNA ploidy separated melanomas from benign melanocytic skin neoplasms with 96.5% accuracy in classifying the grouped cases. The derived nuclear shape factor Form PE and nuclear axis ratio were the most successful discriminants separating DN from MM but allowed only 73.3% correct classification of cases. Separation of DN from CN was best achieved using Form PE and mean nuclear area (74.4% correctly classified). Results from compound nevi in subjects < 25 years of age fell between those for DN and MM. CONCLUSION: Quantitative nuclear cytologic characteristics in sporadic dysplastic nevi span a range seen in common nevi through to those in thin melanomas. Cytologic changes in sporadic dysplastic nevi overlap those seen in other melanocytic skin neoplasms. Therefore, other reproducible morphometric features need to be assessed in order to further refine the histopathologic diagnosis of this entity.

Allelic deletion at chromosome 9p21(p16) and 17p13(p53) in microdissected sporadic dysplastic nevus.

A critical area of chromosomal loss at region p16(9p21-22) and p53(17p13) has been implicated in the genesis of malignant melanoma. It is still unclear whether the genetic alterations can be detected in dysplastic nevus, a premalignant lesion of malignant melanoma. We have searched the frequency of p16 and p53 deletion in nine dysplastic nevi and 13 benign intradermal nevi with five microsatellite markers. Hemizygous deletion was detected in seven of nine (78%) dysplastic nevi at one or more loci for p16 and three of seven (43%) for p53, respectively. No loss of heterozygosity (LOH) was detected in any of the benign intradermal nevi. All three dysplastic nevi with LOH for p53 also showed LOH at p16. However, not all dysplastic nevi showing p16 deletion showed p53 gene deletion. Therefore, these data suggest that deletion of p16 may play an important role in the development of dysplastic nevus as an early event and that the changes may represent an early event in the development of malignant melanoma.

Hair follicle nevi and accessory tragi: variable quantity of adipose tissue in connective tissue framework.

Controversy exists about the histologic differences between hair follicle nevi and accessory tragi. We examined 10 congenital lesions histologically, possible diagnoses of which were hair follicle nevi or accessory tragi. Two specimens out of the 10 had tiny, mature hair follicles surrounded by thick fibrous root sheaths, a few fat cells, and no cartilage. The subcutaneous fat cells of their bases were segmented by a connective tissue framework. They had histologic features of hair follicle nevi. One specimen had cartilage and abundant fat cells with a connective tissue framework in the nodule, as well as a conglomeration of numerous well-differentiated hair follicles. It possessed both elements of a hair follicle nevus and an accessory tragus. Seven specimens had abundant subcutaneous fat and showed a prominent connective tissue framework. These were typical accessory tragi. The present study suggests that the number of fat cells in the nodule or papule differs between these two conditions. All the lesions studied revealed a connective tissue framework in the subcutaneous fat. Histologic features of both hair follicle nevi and accessory tragi can coexist in a single lesion. Hair follicle nevi may represent incomplete accessory tragi with scant fat cells.

Immunohistochemical study of p53 protein expression in Spitz nevus as compared with other melanocytic lesions.

The accumulation of p53 protein was studied immunohistochemically on paraffin-embedded sections of 26 Spitz nevi (SNs), 26 primary invasive cutaneous malignant melanomas (MMs), 20 metastases of MM, and 17 ordinary compound nevi (CNs), using monoclonal antibody BP53-12. Positive reactivity was detected in some of the tumor cells in seven (35%) metastatic MMs, all exhibiting strong nuclear staining; eight (31%) primary MMs, of which seven showed strong nuclear staining; two (7%) SNs, of which only one showed strong nuclear staining; and none of the CNs. The frequencies of the positively stained lesions in general, and the strongly positively stained lesions in particular, in the MM and metastatic MM groups were each statistically significantly higher than the respective frequencies in the SN and CN groups. We believe that the immunohistochemical detection of p53 protein with the use of monoclonal antibodies such as BP53-12 on paraffin sections, especially when strong nuclear reactivity is demonstrated, may prove to be an adjunctive tool in the histopathologic differentiation of MM from SN.

p53 expression is rare in cutaneous melanomas.

Alterations in the tumor-suppressor gene p53 are common in many types of human malignancies, but the potential role of p53 in the pathogenesis of cutaneous melanoma is controversial. The gene product, p53 protein, is normally present in very small amounts in noncancerous tissues. Missense mutations lead to accumulation of mutant p53 in the cells, which makes it detectable immunohistochemically in many cancers. Formalin-fixed, paraffin-embedded sections of 14 primary invasive melanomas, 3 cutaneous melanoma metastases, and 10 predominantly intradermal melanocytic nevi were reacted with a panel of three anti-p53 monoclonal antibodies (mAbs) (PAb240, PAb1801, and DO7) and a mAb against Ki-67 (MIB-1), a marker of cellular proliferation. p53 was not detected in morphologically normal epidermal melanocytes or nevus cells. A single primary invasive melanoma, having a very high index of proliferation (Ki-67 expression in > 50% of cells), had diffuse nuclear labeling with all three anti-p53 mAbs used. Abnormalities of p53 expression occur rarely in cutaneous melanomas, but overexpression of p53 may occur in a subset of melanomas with a high index of proliferation.

Morphometric, DNA, and proliferating cell nuclear antigen measurements in benign melanocytic lesions and cutaneous malignant melanoma.

Morphometric, DNA, and proliferating cell nuclear antigen (PCNA) measurements were taken of benign melanocytic tumors and malignant melanomas. Significant differences between lesion groups according to Krushell-Wallis analysis were found in terms of mean nuclear area, coefficient of variation (cv) of nuclear area, cv of nuclear shape nuclear contour index (NCI), mean and cv of nucleolar area, DNA 2.5 c and 5 c exceeding rates, and PCNA positivity. A logistic regression analysis with respect to banal nevi versus primary malignant melanoma showed that the cv of nuclear area and the DNA 2.5 c exceeding rate were significant independent predictors. Nuclear polymorphism, i.e., the cv of nuclear shape NCI, was larger in metastasizing primary melanomas than in thin nonmetastasizing primary melanomas. PCNA positivity was occasionally increased in keratinocytes adjacent to nevi or melanomas. Larger values for nuclear area, DNA aneuploidy, and PCNA positivity were found in thick malignant melanomas and melanoma metastases than in benign melanocytic lesions and thin malignant melanomas. Morphometry, DNA content, and PCNA positivity thus seem to reflect different stages in tumor progression of malignant melanoma.