Signalling by senescent melanocytes hyperactivates hair growth.

Niche signals maintain stem cells in a prolonged quiescence or transiently activate them for proper regeneration1. Altering balanced niche signalling can lead to regenerative disorders. Melanocytic skin nevi in human often display excessive hair growth, suggesting hair stem cell hyperactivity. Here, using genetic mouse models of nevi2,3, we show that dermal clusters of senescent melanocytes drive epithelial hair stem cells to exit quiescence and change their transcriptome and composition, potently enhancing hair renewal. Nevus melanocytes activate a distinct secretome, enriched for signalling factors. Osteopontin, the leading nevus signalling factor, is both necessary and sufficient to induce hair growth. Injection of osteopontin or its genetic overexpression is sufficient to induce robust hair growth in mice, whereas germline and conditional deletions of either osteopontin or CD44, its cognate receptor on epithelial hair cells, rescue enhanced hair growth induced by dermal nevus melanocytes. Osteopontin is overexpressed in human hairy nevi, and it stimulates new growth of human hair follicles. Although broad accumulation of senescent cells, such as upon ageing or genotoxic stress, is detrimental for the regenerative capacity of tissue4, we show that signalling by senescent cell clusters can potently enhance the activity of adjacent intact stem cells and stimulate tissue renewal. This finding identifies senescent cells and their secretome as an attractive therapeutic target in regenerative disorders.

Transcriptomic analysis of genes associated with vitamin D receptor signalling reveals differences between skin cancers.

Vitamin D activates the vitamin D receptor (VDR), which dimerizes preferentially with the retinoid X receptor-α (RXRα). This heterodimer connects with genetic elements responsive to vitamin D, inhibiting or stimulating gene activity. We performed Nanostring® analysis of VDR/RXRα to compare the mRNA expression of this heterodimer and their correlated transcriptomes in non-melanoma skin cancer (basal cell carcinomas (BCC) and squamous cell carcinomas (SCC)) and melanocytic lesions (intradermal nevi (IN), and melanomas (MM)) with control skin. To evaluate VDR, RXRα and other 22 correlated genes in BCC, SCC, IN and MM, paraffin samples had their transcriptomes analysed using Nanostring®, a platform that allows multiple mRNA analyses. There were 46 samples, including 11 BCC, 10 SCC, 10 IN, 12 MM and 3 pools of control skins. Most mRNAs differed between the lesion groups and the control group. BCC and SCC NCOR2 were upregulated; in MM and IN, RXRγ was higher than in the control group. TP53, FOXO3 and MED1 showed a significant difference when we compared the BCC group to the SCC group. Melanoma and intradermal nevi differed only in AhR. VDR and RXRα were lower than the control in all groups. The panel shows a clear difference between the non-melanocytic cancers and, on the other hand, a slight difference between the melanocytic lesions. The study of vitamin D's influence through its receptor and RXRα is an exciting issue for understanding the importance of this pathway, and the present study can impact the prevention and treatment strategies, mainly in non-melanocytic tumours.

PRAME and Historical Immunohistochemical Antibodies Ki-67, P16, and HMB-45 in Ambiguous Melanocytic Tumors.

ABSTRACT: Ambiguous melanocytic lesions/tumors (AMLs) can be simply described as melanocytic neoplasms that cannot be differentiated as either a melanoma or a nevus. Preferentially expressed antigen in melanoma (PRAME) is a novel antibody that can help differentiate between nevi and melanomas. However, its usefulness remains controversial in AMLs. The aim of this study was to demonstrate the importance of PRAME and diagnostic auxiliary antibodies (Ki-67, p16, HMB-45) in the diagnosis of melanocytic lesions, especially in AMLs. This study included 52 ambiguous melanocytic lesions, 40 nevi, and 40 melanomas. All immunohistochemical studies were performed automatically using the Universal Alkaline Phosphatase Red Detection Kit. Different analytic approaches were used for each antibody based on the literature. Statistically, the multinomial forward stepwise elimination logistic regression analysis was used to create a statistical model to predict the diagnosis of melanocytic lesions based on clinical, morphological, and immunohistochemical data. PRAME positivity was very strong and diffuse in the melanoma group and statistically significantly higher than that of the AML and nevus groups. There was no statistically significant difference between the nevus and AML groups. The Ki-67 proliferation index and HMB-45 staining pattern provided valuable indications for distinguishing between these 3 groups. The P16 antibody was limited in supporting the differential diagnosis. Our statistical model showed that a high mitosis count, central pagetoid spread, and PRAME positivity increased the probability of melanoma against an AML diagnosis. This study showed the advantages of evaluating the PRAME antibody together with morphological features and other immunohistochemical markers (Ki-67 and HMB-45) in the differential diagnosis of melanocytic lesions.

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.

Preferentially expressed antigen in melanoma and p16 expression in acral melanocytic neoplasms.

Acral melanocytic neoplasms often pose diagnostic difficulty. Preferentially expressed antigen in melanoma (PRAME) expression and loss of p16 expression have diagnostic utility in melanocytic tumors. We examined PRAME and p16 expression in 30 acral melanocytic neoplasms (n = 11 nevi; n = 2 dysplastic nevi; n = 7 Spitz nevi; n = 10 acral melanomas). PRAME was scored as % positive nuclei: negative = 0%; 1% to 25% = 1+; 25% to 50% = 2+; 50% to 75% = 3+, or positive: 75% to 100% = 4+. p16 expression was defined as retained (homogeneous or checkerboard) or lost (complete or partial/regionally). PRAME expression was negative in all benign, dysplastic, and Spitz nevi. Conversely, all acral melanomas were diffusely (4+) positive for PRAME expression. p16 expression was retained in all benign acral nevi (8/11 homogeneous, 3/11 checkerboard), completely lost in one dysplastic nevus, and retained in all acral Spitz nevi (3/7 homogeneous, 4/7 checkerboard). p16 was retained in five of 10 acral melanomas (3/10 homogeneous; 2/10 checkerboard), and negative in five of 10 acral melanomas (absent in 3/10, partially lost in 2/10). Our data suggest that 4+ PRAME expression is highly sensitive and specific in the setting of acral melanomas and is a more predictive diagnostic tool compared with p16 immunohistochemistry.

[Application of immunohistochemical staining of PRAME in differential diagnosis between melanoma and melanocytic nevus].

Objective: To investigate the diagnostic value of preferentially expressed antigen in melanoma (PRAME) in differential diagnosis of benign and malignant cutaneous melanocytic lesions. Methods: Fifty-nine cases of melanoma (50 cases of skin primary melanoma, and 9 cases of metastatic melanoma) and 48 cases of melanocytic nevus (40 cases of common nevus and 8 cases of dysplastic nevus) were subject to PRAME immunohistochemistry staining.The difference of PRAME expression between melanoma and melanocytic nevus was analyzed. Results: Among the 50 patients with primary cutaneous melanoma, there were 23 males and 27 females ranging in age from 33 to 87 years (average age 62.4 years, median age 64.5 years). Among the 9 metastatic melanoma there were 7 males and 2 females ranging in age from 40 to 82 years (average age 64 years, median age 65 years). Twenty-six cases (26/50, 52.0%) of cutaneous primary melanoma and 4 cases (4/9) of metastatic melanoma showed diffuse positive PRAME staining. 40 cases (40/40, 100%) of common nevus and 8 (8/8) cases of dysplastic nevus were PRAME negative. Compared with melanocytic nevus group, the melanoma group included more cases with diffuse positive PRAME staining (P<0.05). The sensitivity and specificity of using PRAME to differentiate primary cutaneous melanoma from melanocytic nevus in the cohort is 52.0% and 100%. Conclusions: There is a significant difference in the expression of PRAME between melanoma and melanocytic nevus.Thus, PRAME can be used as an auxiliary diagnostic tool for differentiating benign from malignant cutaneous lesions.

Involvement of mutant and wild-type CYSLTR2 in the development and progression of uveal nevi and melanoma.

BACKGROUND: Activating Gαq signalling mutations are considered an early event in the development of uveal melanoma. Whereas most tumours harbour a mutation in GNAQ or GNA11, CYSLTR2 (encoding G-protein coupled receptor CysLT2R) forms a rare alternative. The role of wild-type CysLT2R in uveal melanoma remains unknown. METHODS: We performed a digital PCR-based molecular analysis of benign choroidal nevi and primary uveal melanomas. Publicly available bulk and single cell sequencing data were mined to further study mutant and wild-type CYSLTR2 in primary and metastatic uveal melanoma. RESULTS: 1/16 nevi and 2/120 melanomas carried the CYSLTR2 mutation. The mutation was found in a subpopulation of the nevus, while being clonal in both melanomas. In the melanomas, secondary, subclonal CYSLTR2 alterations shifted the allelic balance towards the mutant. The resulting genetic heterogeneity was confirmed in distinct areas of both tumours. At the RNA level, further silencing of wild-type and preferential expression of mutant CYSLTR2 was identified, which was also observed in two CYSLTR2 mutant primary melanomas and one metastatic lesion from other cohorts. In CYSLTR2 wild-type melanomas, high expression of CYSLTR2 correlated to tumour inflammation, but expression originated from melanoma cells specifically. CONCLUSIONS: Our findings suggest that CYSLTR2 is involved in both early and late development of uveal melanoma. Whereas the CYSLTR2 p.L129Q mutation is likely to be the initiating oncogenic event, various mechanisms further increase the mutant allele abundance during tumour progression. This makes mutant CysLT2R an attractive therapeutic target in uveal melanoma.

Coexistence of three nevus lipomatosus cutaneus superficialis with typical, cutaneous adenolipoma-like, and dermal spindle cell lipoma-like histopathological features in a patient.

We report an unique case of a patient who showed coexistence of three nevus lipomatosus cutaneus superficialis (NLCS) with typical, cutaneous adenolipoma (AL)-like, and dermal spindle cell lipoma (SCL)-like histopathological features. A 53-year-old woman presented with a 20-year history of skin-colored and slightly elevated nodules. These lesions were separately located on the lateral side (lesion 1) and medial side (lesion 2) of her left buttock and on her right thigh (lesion 3). Microscopically, all were ill-defined dermal lesions with some subcutaneous involvement and were mostly composed of mature adipocytes. The adipocytes formed small aggregates around blood vessels in the upper dermis. Lesions 1, 2, and 3 were diagnosed as NLCS, and additional features were recognized in lesions 2 and 3. Lesion 2 revealed eccrine glands and ducts amongst the lipomatous component, as seen in cutaneous AL. Lesion 3 had scattered CD34-positive spindle cells, which is representative of dermal SCL. These appearances were considered to be on the morphological spectrum of NLCS. In all three lesions, CD34-positive cells proliferated between the upper dermal blood vessels and their peripheral mature adipocytes. This pathological finding could be principal in NLCS and might be associated with its pathogenesis.

The utility of PRAME staining in identifying malignant transformation of melanocytic nevi.

BACKGROUND: PReferentially expressed Antigen in MElanoma (PRAME) immunohistochemical (IHC) staining is used to aid melanoma diagnosis. PRAME expression in nevus-associated melanoma (NAM) has not been evaluated. METHODS: PRAME IHC was applied to cases of NAM; staining for each population of melanocytes (benign and malignant) was graded based on the percentage of labeled cells. No labeling was graded 0, 1% to 25% labeling was 1+, 26% to 50% was 2+, 51% to 75% was 3+, and >76% was 4+. RESULTS: Thirty-six cases were reviewed. Sixty-seven percent (24/36) of melanomas were PRAME positive (4+) while no (0/36) nevi showed 4+ positivity. Eighty-one percent (29/36) of nevi were completely PRAME negative compared to 17% (6/36) of melanomas. In 67% of cases (24/36) PRAME differentiated between benign and malignant melanocyte populations. CONCLUSIONS: We identified a high rate (67%) of differential PRAME staining in adjacent benign and malignant melanocyte populations in NAM. In PRAME positive (4+) melanomas, PRAME differentiates 100% (24/24) of benign and malignant melanocyte populations. When 4+ staining is used as the threshold for positivity, PRAME staining has a sensitivity of 67% (24/36) and a specificity of 100% (36/36). These results support PRAME IHC can assist in distinguishing melanocyte populations in melanoma arising within nevi.

Post Zygotic, Somatic, Deletion in KERATIN 1 V1 Domain Generates Structural Alteration of the K1/K10 Dimer, Producing a Monolateral Palmar Epidermolytic Nevus.

Palmoplantar keratodermas (PPKs) are characterized by thickness of stratum corneum and epidermal hyperkeratosis localized in palms and soles. PPKs can be epidermolytic (EPPK) or non epidermolytic (NEPPK). Specific mutations of keratin 16 (K16) and keratin 1 (K1) have been associated to EPPK, and NEPPK. Cases of mosaicism in PPKs due to somatic keratin mutations have also been described in scientific literature. We evaluated a patient presenting hyperkeratosis localized monolaterally in the right palmar area, characterized by linear yellowish hyperkeratotic lesions following the Blaschko lines. No other relatives of the patient showed any dermatological disease. Light and confocal histological analysis confirmed the presence of epidermolityic hyperkeratosis. Genetic analysis performed demonstrates the heterozygous deletion NM_006121.4:r.274_472del for a total of 198 nucleotides, in KRT1 cDNA obtained by a palmar lesional skin biopsy, corresponding to the protein mutation NP_006112.3:p.Gly71_Gly137del. DNA extracted from peripheral blood lymphocytes did not display the presence of the mutation. These results suggest a somatic mutation causing an alteration in K1 N-terminal variable domain (V1). The deleted sequence involves the ISIS subdomain, containing a lysine residue already described as fundamental for epidermal transglutaminases in the crosslinking of IF cytoskeleton. Moreover, a computational analysis of the wild-type and V1-mutated K1/K10 keratin dimers, suggests an unusual interaction between these keratin filaments. The mutation taster in silico analysis also returned a high probability for a deleterious mutation. These data demonstrate once again the importance of the head domain (V1) of K1 in the formation of a functional keratinocyte cytoskeleton. Moreover, this is a further demonstration of the presence of somatic mutations arising in later stages of the embryogenesis, generating a mosaic phenotype.

Neutralization of HSF1 in cells from PIK3CA-related overgrowth spectrum patients blocks abnormal proliferation.

PIK3CA-related overgrowth spectrum is caused by mosaicism mutations in the PIK3CA gene. These mutations, which are also observed in various types of cancer, lead to a constitutive activation of the PI3K/AKT/mTOR pathway, increasing cell proliferation. Heat shock transcription factor 1 (HSF1) is the major stress-responsive transcription factor. Recent findings indicate that AKT phosphorylates and activates HSF1 independently of heat-shock in breast cancer cells. Here, we aimed to investigate the role of HSF1 in PIK3CA-related overgrowth spectrum. We observed a higher rate of proliferation and increased phosphorylation of AKT and p70S6K in mutant fibroblasts than in control cells. We also found elevated phosphorylation and activation of HSF1, which is directly correlated to AKT activation. Specific AKT inhibitors inhibit HSF1 phosphorylation as well as HSF1-dependent gene transcription. Finally, we demonstrated that targeting HSF1 with specific inhibitors reduced the proliferation of mutant cells. As there is currently no curative treatment for PIK3CA-related overgrowth spectrum, our results identify HSF1 as a new potential therapeutic target.

TERT and TERT promoter in melanocytic neoplasms: Current concepts in pathogenesis, diagnosis, and prognosis.

BACKGROUND AND OBJECTIVE: Located on chromosome locus 5p15.33, telomerase reverse transcriptase (TERT or hTERT) encodes the catalytic subunit of telomerase which permits lengthening and preservation of telomeres following mitosis. Mutations in TERT promoter (TERT-p) upregulate expression of TERT, allowing survival of malignant cells and tumor progression in wide variety of malignancies including melanoma. The objective of this review is to examine the roles of TERT and TERT-p in the pathogenesis, diagnosis, and prognostication of cutaneous melanoma. METHODS: All studies of TERT or TERT-p in cutaneous melanocytic neoplasms with the following inclusion criteria were reviewed: publication date between 2010 and 2019, English language, and series of ≥3 cases were reviewed for evidence supporting the role of TERT in pathogenesis, diagnosis, and prognosis. Studies with <3 cases or focused primarily on mucosal or uveal melanocytic tumors were excluded. RESULTS AND CONCLUSION: TERT-p mutations are frequent in chronic and non-chronic sun damage melanoma and correlate with adverse prognosis, inform pathogenesis, and may provide diagnostic support. While TERT-p mutations are uncommon in acral melanoma, TERT copy number gains and gene amplification predict reduced survival. Among atypical spitzoid neoplasms, TERT-p mutations identify biologically aggressive tumors and support the diagnosis of spitzoid melanoma. TERT-p methylation may have prognostic value in pediatric conventional melanoma and drive tumorigenesis in melanoma arising within congenital nevi. Finally, TERT-p mutations may aid in the differentiation of recurrent nevi from recurrent melanoma.

Ultraviolet radiation accelerates BRAF-driven melanomagenesis by targeting TP53.

Cutaneous melanoma is epidemiologically linked to ultraviolet radiation (UVR), but the molecular mechanisms by which UVR drives melanomagenesis remain unclear. The most common somatic mutation in melanoma is a V600E substitution in BRAF, which is an early event. To investigate how UVR accelerates oncogenic BRAF-driven melanomagenesis, we used a BRAF(V600E) mouse model. In mice expressing BRAF(V600E) in their melanocytes, a single dose of UVR that mimicked mild sunburn in humans induced clonal expansion of the melanocytes, and repeated doses of UVR increased melanoma burden. Here we show that sunscreen (UVA superior, UVB sun protection factor (SPF) 50) delayed the onset of UVR-driven melanoma, but only provided partial protection. The UVR-exposed tumours showed increased numbers of single nucleotide variants and we observed mutations (H39Y, S124F, R245C, R270C, C272G) in the Trp53 tumour suppressor in approximately 40% of cases. TP53 is an accepted UVR target in human non-melanoma skin cancer, but is not thought to have a major role in melanoma. However, we show that, in mice, mutant Trp53 accelerated BRAF(V600E)-driven melanomagenesis, and that TP53 mutations are linked to evidence of UVR-induced DNA damage in human melanoma. Thus, we provide mechanistic insight into epidemiological data linking UVR to acquired naevi in humans. Furthermore, we identify TP53/Trp53 as a UVR-target gene that cooperates with BRAF(V600E) to induce melanoma, providing molecular insight into how UVR accelerates melanomagenesis. Our study validates public health campaigns that promote sunscreen protection for individuals at risk of melanoma.

Abrogation of BRAFV600E-induced senescence by PI3K pathway activation contributes to melanomagenesis.

Human melanocytic nevi (moles) are benign lesions harboring activated oncogenes, including BRAF. Although this oncogene initially acts mitogenically, eventually, oncogene-induced senescence (OIS) ensues. Nevi can infrequently progress to melanomas, but the mechanistic relationship with OIS is unclear. We show here that PTEN depletion abrogates BRAF(V600E)-induced senescence in human fibroblasts and melanocytes. Correspondingly, in established murine BRAF(V600E)-driven nevi, acute shRNA-mediated depletion of PTEN prompted tumor progression. Furthermore, genetic analysis of laser-guided microdissected human contiguous nevus-melanoma specimens recurrently revealed identical mutations in BRAF or NRAS in adjacent benign and malignant melanocytes. The PI3K pathway was often activated through either decreased PTEN or increased AKT3 expression in melanomas relative to their adjacent nevi. Pharmacologic PI3K inhibition in melanoma cells suppressed proliferation and induced the senescence-associated tumor suppressor p15(INK4B). This treatment also eliminated subpopulations resistant to targeted BRAF(V600E) inhibition. Our findings suggest that a significant proportion of melanomas arise from nevi. Furthermore, these results demonstrate that PI3K pathway activation serves as a rate-limiting event in this setting, acting at least in part by abrogating OIS. The reactivation of senescence features and elimination of cells refractory to BRAF(V600E) inhibition by PI3K inhibition warrants further investigation into the therapeutic potential of simultaneously targeting these pathways in melanoma.

RAB27A promotes melanoma cell invasion and metastasis via regulation of pro-invasive exosomes.

Despite recent advances in targeted and immune-based therapies, advanced stage melanoma remains a clinical challenge with a poor prognosis. Understanding the genes and cellular processes that drive progression and metastasis is critical for identifying new therapeutic strategies. Here, we found that the GTPase RAB27A was overexpressed in a subset of melanomas, which correlated with poor patient survival. Loss of RAB27A expression in melanoma cell lines inhibited 3D spheroid invasion and cell motility in vitro, and spontaneous metastasis in vivo. The reduced invasion phenotype was rescued by RAB27A-replete exosomes, but not RAB27A-knockdown exosomes, indicating that RAB27A is responsible for the generation of pro-invasive exosomes. Furthermore, while RAB27A loss did not alter the number of exosomes secreted, it did change exosome size and altered the composition and abundance of exosomal proteins, some of which are known to regulate cancer cell movement. Our data suggest that RAB27A promotes the biogenesis of a distinct pro-invasive exosome population. These findings support RAB27A as a key cancer regulator, as well as a potential prognostic marker and therapeutic target in melanoma.

Somatic Mutations in NEK9 Cause Nevus Comedonicus.

Acne vulgaris (AV) affects most adolescents, and of those affected, moderate to severe disease occurs in 20%. Comedones, follicular plugs consisting of desquamated keratinocytes and sebum, are central to its pathogenesis. Despite high heritability in first-degree relatives, AV genetic determinants remain incompletely understood. We therefore employed whole-exome sequencing (WES) in nevus comedonicus (NC), a rare disorder that features comedones and inflammatory acne cysts in localized, linear configurations. WES identified somatic NEK9 mutations, each affecting highly conserved residues within its kinase or RCC1 domains, in affected tissue of three out of three NC-affected subjects. All mutations are gain of function, resulting in increased phosphorylation at Thr210, a hallmark of NEK9 kinase activation. We found that comedo formation in NC is marked by loss of follicular differentiation markers, expansion of keratin-15-positive cells from localization within the bulge to the entire sub-bulge follicle and cyst, and ectopic expression of keratin 10, a marker of interfollicular differentiation not present in normal follicles. These findings suggest that NEK9 mutations in NC disrupt normal follicular differentiation and identify NEK9 as a potential regulator of follicular homeostasis.

Leukoderma induced by rhododendrol is different from leukoderma of vitiligo in pathogenesis: A novel comparative morphological study.

BACKGROUND: Rhododendrol (rhododenol), an inhibitor of tyrosinase activity, is used as a skin-whitening component. Many cases of leukoderma after the application have been reported, termed rhododenol-induced leukoderma (RIL). The aim of this study was to clarify the pathogenesis of RIL morphologically through comparison with vitiligo. METHODS: We examined 14 cases of RIL and 15 cases of vitiligo using routine histopathology and immunohistochemistry. Thirteen cases of RIL, six cases of vitiligo and specimens of the RIL mouse model were evaluated by electron microscopy. RESULTS: There were common findings in RIL and vitiligo at the light-microscopic level: (a) vacuolar changes in the dermo-epidermal junction, (b) melanophages in the papillary dermis, (c) perifollicular lymphocyte infiltration, (d) loss or decrease of basal melanin pigment and (e) decrease of melanocytes in the lesions. The ultrastructural observations showed specific findings of RIL: (a) remaining melanocytes in depigmented lesions, (b) inhomogeneous melanization in melanocytes and (c) degenerated melanosomes in melanocytes. Some of the findings were observed in a RIL mouse model. Furthermore, it is notable that cell organelles of melanocytes were intact in our RIL cases. CONCLUSION: Morphological changes of RIL targeting melanosomes in melanocytes without degeneration of organelles reflect the reversible clinical course of most cases.

Depletion of primary cilium in acral melanoma.

BACKGROUND: A eukaryotic cell's primary cilium (PC) is critical for cell signaling, migration and homeostasis. Primary cilium dysfunction has been demonstrated in several malignancies, but whether primary cilia loss occurs in acral melanoma has remained unknown. To address this, we examined the ciliation index (% melanocytes containing a PC) of patient-derived, biopsy-proven acral melanoma and compared these to benign acral nevi. METHODS: We generated a pilot initiative study that included six acral melanomas and seven acral nevi derived from the foot. Using fluorescent immunohistochemistry, we calculated ciliation indexes of Sox10+ melanocytes. RESULTS: Average ciliation index for acral nevi was 74.0% (SE of the mean [SEM] 3.3%) vs 9.3% for acral melanoma (SEM 5.7%), finding a statistically significant difference between the groups (P-value <.001, two tailed t test). CONCLUSION: The data show a significant loss of primary cilia in malignant acral melanoma vs benign acral nevi, suggesting that cilia may play an important role during acral melanoma formation. Our data, which should be validated by a larger study with longer follow-up period, suggest that examining ciliation index may be a useful diagnostic test when distinguishing benign acral nevi from melanoma.

Immunohistochemistry of p16 in nevi of pregnancy and nevoid melanomas.

BACKGROUND: Hormonal changes in pregnancy are known to alter melanocytic lesions, with some nevi noted to have increased mitotic figures and increased Ki-67 proliferation index. Additionally, cytomorphologic changes have also been noted, referred to as superficial micronodules of pregnancy. These changes may alarm the pathologist for malignancy, particularly nevoid melanoma. Immunohistochemistry for p16 has been recently utilized to distinguish benign nevi from melanoma. We assessed the use of p16 immunohistochemistry for distinguishing melanocytic nevi of pregnant patients from nevoid melanomas. METHODS: Fourteen nevomelanocytic lesions were obtained from pregnant or postpartum patients along with 20 nevoid melanomas for comparison. Immunohistochemistry with p16 was performed on each melanocytic lesion. The percentage of nuclear p16 staining of dermal melanocytes was grouped on a scale of <5%, 5% to 25%, >25% to 50%, and >50%. RESULTS: The majority of nevi from pregnant patients (81%) showed staining of >5% for p16. In contrast, the majority of nevoid melanomas (65%) had staining of <5% for p16. CONCLUSION: The application of p16 as a potential immunohistochemistry diagnostic marker to distinguish nevi from pregnant patients vs nevoid melanomas may be useful.

Wiesner Nevus of the Eyelid.

A healthy 31-year-old female presented with an elevated vascular lesion on the right lower eyelid margin. Histology results from excisional biopsy demonstrated a range of intradermally nested atypical melanocytes with negative staining for BRCA1-associated protein 1, confirming the diagnosis of Wiesner nevus. Wiesner nevi may be a cutaneous hallmark of the BRCA1-associated protein 1-associated cancer susceptibility syndrome, and to our knowledge, this is the first report of such a lesion presenting anywhere on the ocular adnexa.