Expression of vascular endothelial growth factor in early cutaneous melanocytic lesion progression

BACKGROUND: A considerable body of evidence supports the concept that a significant number of cutaneous malignant melanomas progress through a precursor lesion or dysplastic melanocytic nevi (DN). Tumor angiogenesis likely plays a critical role in early development of melanoma, and intermediate biomarkers of angiogenesis could be useful as chemoprevention and prognostic markers. METHODS: Markers of angiogenesis that included expression of the vascular endothelial growth factor A (VEGF-A) and microvessel density counts (MVD) were evaluated in 13 prospectively collected benign nevi (BN) and 19 DN from 16 individuals and in a comparison group of 17 primary melanomas (16 archival samples and 1 prospective melanoma). RESULTS: VEGF expression in melanocytic cells (mean+/-standard error [SE]) was low or absent in BN (3.4+/-1.4), increased significantly in DN (41.0+/-10.1; P=.0003 for BN vs DN), and increased further in primary melanoma (119.9+/-28.3; P = .06 for DN vs melanoma). MVD using CD31 (mean+/-SE [percentage x intensity]) followed a similar pattern with similarity between BN (2.6+/-0.7; N=13) and DN (2.2+/-0.8; N=19; P=.4 for BN vs DN), whereas primary melanomas were significantly higher (39.4+/-6.4; N=17; P=.0001 for BN or DN vs melanoma). CONCLUSIONS: In a prospective setting, the current data suggested that increased VEGF-A expression in DN may be a good indicator of preneoplastic change in melanocytic lesions with the potential for improving the understanding and prevention of the transformation of DN to melanoma.     

Skin cancer in Egypt: a word in your ear

BACKGROUND AND OBJECTIVES: In Egypt, the clinicopathologic features of skin cancer are still unknown. MATERIALS AND METHODS: To define these features, registries of the Pathology Departments, Assiut and South Valley University Hospitals were reviewed. The lesions included 21 melanomas, 39 squamous cell carcinomas (SCCs), and 202 basal cell carcinomas (BCCs). RESULTS: Skin cancer represented 5% of the malignant tumors of the entire body. BCC (77%) was the most common skin cancer followed by SCC (15%) and melanomas (8%). The mean age was 54 +/- 3 (melanomas), 66 +/- 10 (BCC), and 60 +/- 5.18 (SCC). The most common sites were the face (BCCs), face and extremities (SCCs), and face and lower limbs (melanomas). The average size (mm) was 21 +/- 0.3 (melanomas), 28 +/- 0.3 (BCC) and 30 +/- 1.1 (SCC). Melanomas, BCCs and SCCs were of nodular, keratotic invasive and nodular infiltrative types, respectively. CONCLUSIONS: In Egypt, skin cancer is uncommon malignancy. As compared to Western societies, the incidence rate of melanoma is very low and its topographic distribution is different. Alternatively, the rates for SCCs/BCCs are comparably high and their topographic distribution is similar. This is the first investigation that reports the clinicopathologic features of skin cancer in Egypt and compares it to other parts of Africa and Western societies.     

Cyclooxygenase-2 (COX-2): first immunohistochemical marker distinguishing early cutaneous melanomas from benign melanocytic skin tumours

We have reported recently that changes in expression level of COX-2 are correlated with development and progression of human melanoma. In this study, we investigated whether the COX-2 expression level might be a useful immunohistochemical marker for distinguishing cutaneous melanomas from benign melanocytic lesions. Up to now, immunohistochemical markers have not ensured satisfactory sensitivity and specificity of differential pathologic diagnosis of melanoma. The expression of COX-2 was determined immunohistochemically in formalin-fixed, paraffin-embedded specimens of 33 early Clark I/II melanomas and 58 naevi. Mean COX-2 expression in melanomas was significantly stronger than in naevi (P approximately 10(-13)). A simple diagnostic algorithm using threshold values of the COX-2 expression level allows for differentiation between early melanomas and naevi with high sensitivity (Se) and specificity (Sp) (for Se between 91 and 100%, Sp values change between 96.5 and 51.7%). Areas under the receiver operating characteristic curves were, respectively, 0.97+/-0.02 and 0.86+/-0.04 for the COX-2 expression in central and border regions of the lesions. For all the melanomas (not only the early ones),the respective areas under the ROC curve values were 0.98+/-0.01 and 0.97+/-0.02. In conclusion, COX-2 is the first immunohistochemical marker that allows the distinguishing of early melanomas from benign melanocytic lesions with both high sensitivity and specificity.     

Epiluminescence microscopy features of cutaneous malignant melanoma metastases

Especially small and/or initial cutaneous malignant melanoma metastases (CMMMs) are tumours with inconspicuous clinical and sometimes histological features which may be difficult to differentiate from benign melanocytic lesions or angiomas. Thus it would be very valuable to have additional criteria for the differential diagnosis of such lesions. Thirty histologically verified CMMMs were examined using epiluminescence microscopy (ELM) in order to visualize a large number of morphological features permitting the recognition of malignancy. One hundred primary cutaneous malignant melanomas (PCMMs), 50 dysplastic naevi, 50 common naevi, 30 blue naevi and 20 haemangiomas served as the control group; these were randomly selected from a large data base and were all reviewed for histological diagnosis. Four of the 24 features studied were shown to differ significantly between CMMMs and the control group. Two features of the malignant tumour group (CMMM and PCMM) differed significantly from the benign tumour group. A polymorphic angiectatic base pattern and/or vascular aneurysms, peripheral erythema, brown-grey coloration as a negative criterion (i.e. its absence is indicative of CMMM) and a light brown halo had a specificity of 86.7-96.0% for CMMM. Areas of polymorphic and/or horizontally dilated capillaries and a saccular pattern had a specificity of 97.3-99.2% for the malignant group (CMMM and PCMM). Three features - peripheral greyish patches, lesions surrounded by grey streaks (melanoma cell infarcts of the vessels) and microscopic ovoid blood lakes (spontaneous microhaemorrhages)--were absent in the benign group. The prevalence of distinct ELM criteria in CMMM represents a useful enhancement for the diagnosis of malignancy in melanocytic skin lesions.     

Fluorescence in situ hybridization (FISH) evaluation of chromosomes 6, 7, 9 and 10 throughout human melanocytic tumorigenesis

Loss of the 9p21 region, 6q and 10q and gain of chromosome 7 are the most frequent chromosomal abnormalities found in human melanomas, but very few cytogenetic data are available regarding dysplastic and common naevi. To study the occurrence of the most consistent chromosomal changes during melanocytic tumorigenesis, archival samples from 30 common naevi and 30 naevus-associated melanomas were analysed by interphase fluorescence in situ hybridization (FISH) using centromeric probes for chromosomes 9 and 7 and locus-specific probes for 9p21, 6q11.1, 6q24.1, 10p15.3 and 10q23.1 regions. In naevus-associated melanomas, separate evaluations were made for sectors corresponding to residual naevus, dysplastic naevus, radial growth phase melanoma and vertical growth phase melanoma. No chromosomal aberrations were found in common naevi, but monosomy 7 was observed in one case. In naevus-associated melanomas, loss of the entire chromosome 9 or of the 9p21 region was observed in 56% of common and 54% of dysplastic naevus sectors, in 64% of radial growth phase melanoma and in 82% of vertical growth phase melanoma. Loss of the long arm of chromosome 6, monosomy 10 and deletion 10q were exclusively confined to radial (18% for both chromosomes) and vertical (29 and 59%, respectively) growth phase melanomas. Polysomy of chromosome 7 was detected only in melanoma sectors (radial growth phase, 14%; vertical growth phase, 59%). The high incidence of 9p21 loss in melanoma-associated naevi, which is maintained in all evolutionary phases of melanocytic tumorigenesis, and the complete absence of chromosomal aberrations in common naevi, strongly suggest that 9p21 loss may be regarded as a cytogenetic marker of melanocytic naevi with a high potential for progression.     

Melanoma with benign melanocytic naevus components: reappraisal of clinicopathological features and prognosis

The clinicopathological features and prognosis of primary cutaneous malignant melanoma with benign melanocytic naevus (BMN) components are still under debate. The purpose of this study was to characterize further the clinical and histopathological features of naevus-associated melanomas, with emphasis on the BMN components, and to examine their prognosis based on a large series. Following a histopathological review of 667 consecutive cases of primary cutaneous melanoma, 148 melanomas with BMN components (22.1%) were identified for further study. A control group of 519 melanomas without BMN components seen in a similar period were also studied. Clinically, patients with melanomas containing BMN components (n = 148; age range 25-86 years, mean age 54 +/- 16 years; male to female ratio 1:1.02) presented with tumours located mainly on the trunk (34.5%), followed by the upper extremities (24.3%), lower extremities (20.3%), and head and neck (14.2%). Compared with tumours without BMN components (n = 519; age range 19-89 years, mean age 57 +/- 15 years; male to female ratio 1:1.3), melanomas with BMN components occurred in slightly younger individuals (P = 0.027). Histopathologically, BMN components mainly showed features of acquired naevi (total 87 cases; dysplastic, 80 cases; banal, seven cases) or congenital naevi (total 57 cases; superficial, 56 cases; deep, one case), but a minority of these lesions (four cases) could not be further subcategorized. Generally, melanomas containing BMN components were relatively thinner than melanomas without BMN components (mean Breslow index 0.95 +/- 0.83 mm and 1.3 +/- 1.6 mm, respectively) (P = 0.015). The follow-up data available in 69 patients with naevus-associated melanomas consistently revealed a relatively good outcome (5 year metastasis-free survival rate 93.75%), although no statistical difference in prognosis was observed between this group and a subset of 283 melanomas patients without BMN components stratified by tumour thickness. We conclude that BMN components in naevus-associated melanomas constitute a heterogeneous group morphologically, consisting mainly of dysplastic and superficial congenital naevi. This finding indicates a more important role for superficial congenital naevus as a precursor lesion of naevus-associated melanomas than presently recognized. Patients with naevus-associated melanomas generally show a good clinical outcome, reflecting their small Breslow index.     

Structural asymmetry as a dermatoscopic indicator of malignant melanoma--a latent class analysis of sensitivity and classification errors

Asymmetry of pigmented skin lesions is an important indicator of possible malignant melanoma and contributes substantially to the diagnosis of melanoma in the dermatoscopic ABCD rule for melanocytic lesions and other algorithms. However, it may be observer dependent. Dermatoscopic asymmetry cannot be assessed objectively and no golden standard of asymmetry diagnosis exists. The aim of this study was to assess the sensitivity of axis (a-) symmetry using latent class analysis. We analysed ratings from four experts in dermatoscopy of 232 pigmented lesions by latent class analysis (LCA). Possible ratings were 'no asymmetry', 'asymmetry in one axis' and 'asymmetry in two axes'. A subset of melanocytic lesions (blue naevi excluded) was analysed. Based on LCA, the asymmetry of the singular lesion was determined. The sensitivity of 'no asymmetry' was 40-77%, 40-70% for one-axis asymmetry, and 77-92% for two-axes asymmetry. Overestimation of asymmetry was more common than underestimation. Melanomas were significantly more asymmetric than pigmented naevi, atypical naevi and papillomas, but not basal cell cancers. Analysis of the melanocytic subset gave similar results. The median asymmetry of malignant melanomas (1.67, interquartile range 1.81-1.99) was higher than for melanocytic naevi. In conclusion, asymmetry and symmetry are important criteria for diagnosing or excluding malignant melanoma using the dermatoscopic ABCD rule, risk stratification and other diagnostic rules. Using LCA, we minimized observer dependence in the assessment of axis (a-) symmetry. LCA, besides conceptualizing the diagnostic process, enables the assignment of lesions to their true diagnostic class.     

In situ analysis of transforming growth factor-{beta}s (TGF-{beta}1, TGF-{beta}2, TGF-{beta}3and TGF-3 type II receptor expression in malignant melanoma

We have analysed, by in situ hybridization, mRNA expressionof TGF-ß1, TGF-ß2, TGF-ß3, andof TGF-ß type II receptor in benign melanocytic naevi,primary melanomas, and in skin metastases of malignant melanomas.Our results show that melanoma progression correlates with overexpressionof TGF-ß. All skin metastases and most primary melanomasinvasive to Clark's level IV-V revealed specific TGF-ß2mRNA and protein expression. However, expression of this cytokinewas not observed in benign melanocytic lesions and was detectedonly in one of five early primary melanomas investigated. Someprimary melanomas and skin metastases also revealed specificTGF-ß1 mRNA signals although expression of this isoformwas not found in benign naevi. TGF-ß3 expression,which was only barely detectable in benign melanocytic lesions,was enhanced in some skin metastases. Interestingly, the epidermisoverlaying melanomas revealed lower levels of TGF-ß3mRNA expression than epidermis of healthy skin or epidermisadjacent to benign naevi, thereby suggesting that paracrinemechanisms between tumour cells and keratinocytes may influencemelanoma development. In primary melanomas TGF-ß typeII receptor mRNA signals were much more heterogeneously distributedwhen compared to benign melanocytic naevi, suggesting variabledegrees of TGF-ß resistance among melanoma cells withinindividual lesions. However, melanoma progression appeared notto be correlated with a complete loss of TGF-ß typeII receptor gene expression, since all skin metastases revealedclearly detectable although heterogeneous levels of TGF-ßtype II receptor mRNA expression.     

VEGF and VEGFR-2 immunohistochemistry in human melanocytic naevi and cutaneous melanomas

Vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-2 (VEGFR-2) play a key role in vasculogenesis and angiogenic sprouting, which are crucial for tumour development and metastasis. In order to determine their possible role in the acquisition of metastatic potential throughout melanocytic tumour progression, VEGF and VEGFR-2 immunohistochemical expression were evaluated in 36 human melanocytic tumours of the skin (24 malignant melanomas and 12 common naevi). Different VEGFR-2 immunostaining patterns were detected in the vast majority of melanomas (21/24; 88%). A nuclear membrane-like pattern was mainly associated with in situ and microinvasive melanomas, whereas a combined cytoplasmic membrane and nuclear membrane-like pattern was seen in invasive melanomas. A nuclear membrane-like pattern was also observed in 83% (10/12) of common naevi. Cytoplasmic immunostaining for VEGF was observed in 72% (8/11) of in situ/microinvasive melanomas, 84% (11/13) of invasive melanomas and 91% (11/12) of naevi. CD31 was also investigated as an immunohistochemical marker for microvessel density (MVD) evaluation. No associations were found between MVD and VEGF/VEGFR-2 expression. Taken together, these data indicate that VEGF production is a common event in benign melanocytic tumours, whereas VEGFR-2 expression, co-localized in the cytoplasmic and nuclear membrane, is associated with progression towards invasive melanoma. The role exerted by VEGF/VEGFR-2, however, seems to be independent of the development of a tumour-related capillary network.     

The value of cyclooxygenase-2 expression in differentiating between early melanomas and histopathologically difficult types of benign human skin lesions

Early cutaneous melanomas may present a substantial diagnostic challenge. We have already reported that expression of cyclooxygenase-2 (COX-2) may be useful for differentiating between cutaneous melanomas and naevi. The purpose of this study was to examine the value of COX-2 in a challenging task of differential diagnosis of early melanomas and melanocytic naevi considered by histopathologists as morphologically difficult to unequivocally diagnose as benign lesions. The material for the study comprised formalin-fixed paraffin-embedded samples of 46 naevi (including 27 cases of dysplastic, Spitz and Reed naevi) and 30 early human cutaneous melanomas. The expression of COX-2 was detected immunohistochemically. Melanomas expressed COX-2 significantly more strongly compared with naevi. The test, on the basis of determination of the percentage fractions of COX-2-positive cells, allows for differentiation of early skin melanomas and naevi with high sensitivity and specificity. Receiver operating characteristic analysis of the test results yielded areas under receiver operating characteristics curves (AUC)=0.946±0.030 for central regions and AUC=0.941±0.031 for the peripheries of the lesions. The performance of the test in differentiating between melanomas and the naevi group comprising dysplastic, Spitz and Reed naevi was also good, with AUC=0.933±0.034 and 0.923±0.037 for the central and the border regions of the lesions, respectively. Using a more complex diagnostic algorithm also accounting for the staining intensity did not result in an improvement in the resolving power of the assay. A diagnostic algorithm using differences in the percentage fractions of cells expressing COX-2 may serve as a useful tool in aiding the differential diagnosis of 'histopathologically difficult' benign melanocytic skin lesions and early melanomas.     

Dermatoscopic differences between atypical melanocytic naevi and thin malignant melanomas

Dermatoscopy is used to aid in the differential diagnosis of pigmented skin lesions. The aim of this study was to identify dermatoscopic differences between atypical melanocytic naevi and thin malignant melanomas. A set of 180 difficult cases (60 thin melanomas, 120 clinically atypical benign melanocytic naevi) was analysed. Differences in structure, distribution of pigmentation, presence or absence of important structures, total number of colours and asymmetry of the lesions were identified. The three-structure type, multifocal distribution of pigmentation, eccentric peripheral hyperpigmentation, multiple colours (three or more) and asymmetry of structures/colours in the dermatoscopic image were considerably more frequent in melanomas than in benign lesions (P<0.001, chi-squared test). No single dermatoscopic criterion exists to discriminate between all melanocytic lesions with sufficient confidence. Some criteria are helpful in the differential diagnosis and management of difficult cases.     

Magnetic resonance imaging in the diagnosis of melanoma: in vivo preliminary studies with dynamic contrast-enhanced subtraction

The aim of this study was to analyse the potential of fast dynamic subtraction magnetic resonance (MR) imaging in differentiating in vivo melanomas from benign melanocytic lesions. Dynamic MR imaging was performed after intravenous administration of gadopentetate dimeglumine (Gd-DTPA) in 18 patients with melanocytic skin lesions. Using a post-processing algorithm, time-signal intensity curves were obtained for the lesions and classified according to their shapes as type I (steady enhancement increase), type II (plateau of signal intensity) or type III (wash-out of signal intensity). Other parameters evaluated for their potential to differentiate melanomas from benign lesions were the enhancement rate (percentage of signal intensity increase) in the first minute after Gd-DTPA administration, the peak value of the enhancement rate, and the wash-out slope. The pigmented lesions were then surgically excised and the MR results compared with the histological assessment. In melanomas, the mean value of the enhancement rate in the first minute was 611%, whereas in benign lesions it was 131% (P = 0.001). The distribution of curve types was also different: seven of the nine naevi showed type I curves, while eight of the nine melanomas displayed a type III curve. In addition, distinctive wash-out dynamics were observed: the enhancement rate began to decrease between the first and third minutes for melanomas, but continued to increase until the sixth minute for naevi (P = 0.000). These findings, which are most likely related to the neoangiogenesis present in melanomas, indicate that dynamic MR imaging can be helpful in the differential diagnosis of pigmented skin lesions.     

Detection of microsatellite alterations in the spectrum of melanocytic nevi in patients with or without individual or family history of melanoma

We studied a group of patients with or without individual or family history of melanoma for the occurrence of genetic alterations at microsatellite DNA sequences, usually referred to as microsatellite instability (MSI), and loss of heterozygosity (LOH). Microsatellite analysis of 3 markers located on chromosome 9p21-22 was performed for 88 melanocytic lesions, including 27 melanomas and 35 dysplastic and 26 common nevi, from 48 patients. Three additional markers, on 11q23, 17q21 and 5q22, were investigated in 16 melanomas. Overall, microsatellite alterations of the type usually considered low-level instability at 9p21-22 were observed in 22% of melanomas and 31% of dysplastic and 23% of common nevi. LOH at the same loci was found in 15% of melanomas and 8% of dysplastic nevi but never in common nevi. Cases with a positive family history of melanoma compared to those with a negative family history showed a higher microsatellite alteration frequency (43% vs. 20%), and the same was observed in melanoma compared to non-melanoma carriers (31% vs. 16%). Our results show that (i) MSI is common in all melanocytic lesions, though with differences in the group of patients which could have clinical relevance if confirmed, whereas LOH is restricted to melanomas and dysplastic nevi; (ii) various melanocytic lesions from the same patient represent clonally distinct tumors; (iii) the phenotype suggestive of DNA repair deficiency is influenced by a family or an individual history of melanoma; (iv) the microsatellite alteration frequency correlates with patient groups ordered according to increasing melanoma risk.     

Linear discriminant analysis of dermoscopic parameters for the differentiation of early melanomas from Clark naevi

As a first step to develop a screening system for pigmented skin lesions, we performed digital discriminant analyses between early melanomas and Clark naevi. A total of 59 cases of melanoma, including 23 melanoma in situ and 36 thin invasive melanomas (Breslow thickness < or =0.75 mm), and 188 clinically equivocal, histopathologically diagnosed Clark naevi were used in our study. After calculating 62 mathematical variables related to the colour, texture, asymmetry and circularity based on the dermoscopic findings of the pigmented skin lesions, we performed multivariate stepwise discriminant analysis using these variables to differentiate melanomas from naevi. The sensitivities and specificities of our model were 94.4 and 98.4%, respectively, for discriminating between melanomas (Breslow thickness < or =0.75 mm) and Clark naevi, and 73.9 and 85.6%, respectively, for discriminating between melanoma in situ and Clark naevi. Our algorithm accurately discriminated invasive melanomas from Clark naevi, but not melanomas in situ from Clark naevi.     

Evaluation of DNA ploidy and degree of DNA abnormality in benign and malignant melanocytic lesions of the skin using video imaging

BACKGROUND: Making a morphologic distinction between benign and malignant melanocytic tumors of the skin is frequently difficult, especially because "gray zones" between these lesions often exist. DNA image cytometry as an adjuvant method for the diagnosis and prognostic prediction of premalignant lesions and malignant tumors of many other organs is already well established. The aim of this study was to determine whether DNA image cytometry is helpful in distinguishing benign from malignant melanocytic lesions and whether cytometry would give valid information with which to predict the prognoses associated with malignant melanomas. METHODS: DNA image cytometry was performed on 127 benign and 58 primary maligant melanomas of the skin as well as 11 metastatic melanomas, using an enzymatic single cell solution according to a method described by Heiden et al. in Cytometry (1991;12:614-21). RESULTS: DNA aneuploidy was graded by DNA index (DI) and a 2c deviation index (2cDI). In contrast to benign melanocytic lesions (with 16% DNA aneuploidy), primary and metastatic malignant melanomas had significantly higher frequencies of DNA aneuploidy (86% and 73%, respectively). In the degree of DNA aneuploidy, significant differences between benign and malignant melanocytic tumors could be observed. The mean 2cDI of aneuploid benign lesions was 1.0, whereas the primary malignant melanomas had a mean 2cDI of 2.92 and the metastatic melanomas a mean of 6.9. The frequency of DNA aneuploidy increased with Breslow thickness. Twenty-one patients with primary malignant melanoma developed metastases. All metastasizing primary tumors were aneuploid and showed a significantly higher grade of DNA aneuploidy than nonmetastasizing malignant melanomas. Moreover, none of the diploid malignant melanomas developed metastases. CONCLUSIONS: This study reveals that DNA image cytometry is prognostically and diagnostically relevant to the evaluation of melanocytic lesions of the skin. Nevertheless, it cannot be relied on alone to provide enough information for a diagnosis.     

Multiple primary cutaneous melanomas.

BACKGROUND. Development of multiple primary cutaneous melanomas is a well-recognized phenomenon. As with single primary melanoma, personal and family histories of melanoma and dysplastic nevi (DN) are considered important risk factors. The natural history and impact of regular follow-up evaluation of this entity were examined. METHOD. Through a search of the computerized data bank of the Pathology Department and the Melanoma Registry of the Pigmented Lesion Clinic at Massachusetts General Hospital, 41 patients with multiple cutaneous melanomas were identified. RESULTS. Mean (+/- standard error) age at first diagnosis was 49 +/- 2 years (range, 21-75 years). The male to female ratio was 2:1. The median number of primary melanomas was two (88%). Three patients had three and one had five. Melanoma types included superficial spreading (70%), nodular (8%), lentigo maligna (2%), and unclassified (10%), and in 7% the type was unknown. Nineteen (46%) patients had histologic and/or clinical evidence of DN. For the group with DN, the mean age at first diagnosis (44 +/- 3 years) was significantly less than that of patients without DN (54 +/- 3 years) (P less than 0.05). Family history of melanoma was found in 10 patients (24%). Multiple melanomas were diagnosed concurrently in 16 patients (39%), whereas in 25 (61%) diagnosis was sequential. For the latter group, the mean tumor thickness from the first (1.21 +/- 0.28 mm) to the second melanoma (0.51 +/- 0.08 mm) decreased significantly (P less than 0.05); the median time interval was 36 months (range, 2-372 months). CONCLUSION. These data confirm the need for complete skin examination for patients with newly diagnosed melanoma; and, with subsequent melanomas appearing as long as 31 years after the first melanoma, continued follow-up with complete skin examinations seems prudent.     

Immunohistochemical investigation of alpha1 (IV) and alpha5 (IV) collagen chains in a broad spectrum of melanocytic tumours

BACKGROUND: Cells of melanocytic naevi and cutaneous malignant melanomas (MM) are surrounded by a basement membrane (BM). AIM: To scrutinize any difference between the deposits of alpha1 (IV) and alpha5 (IV) collagen chains in melanocytic naevi and MM. METHODS: A total of 27 common melanocytic naevi, 11 dysplastic naevi, 21 atypical naevi (melanocytomas) including Spitz and non-Spitz types, as well as 24 MM were studied. Their phenotypic and functional characteristics defined by immunohistochemistry using a panel of antibodies, including those directed to the alpha1 (IV), alpha3 (IV) and alpha5 (IV) collagen chains. RESULTS: Almost all naevi and half the melanocytomas exhibited a strong positivity for the alpha1 (IV) collagen chain. By contrast, the remaining melanocytomas and MM presented a heterogeneous staining pattern for the alpha1 (IV) collagen chain. One third of the naevi, 23% of the MM without cutaneous micrometastasis and 83% of MM with cutaneous micrometastasis showed discrete cytoplasmic positivity for the alpha5 (IV) collagen chain. All other melanocytic tumours were negative for this antibody. Rare MM cells in transepidermal migration were stained with the anti-alpha1 (IV) or alpha5 (IV) collagen chain antibodies. No immunoreactivity for the alpha3 (IV) collagen chain was disclosed in any of the samples. CONCLUSION: We report the expression of alpha1 (IV) and alpha5 (IV) collagen chains in naevi and MM. The inconsistent staining pattern for alpha1 (IV) collagen chain in phenotypically atypical melanocytomas and in MM highlight the heterogeneity in both cell differentiation and stroma-tumour interactions. This biological aspect may be related to neoplastic progression and influence metastatic potential.     

Cellular senescence in naevi and immortalisation in melanoma: a role for p16?

Cellular senescence, the irreversible proliferative arrest seen in somatic cells after a limited number of divisions, is considered a crucial barrier to cancer, but direct evidence for this in vivo was lacking until recently. The best-known form of human cell senescence is attributed to telomere shortening and a DNA-damage response through p53 and p21. There is also a more rapid form of senescence, dependent on the p16-retinoblastoma pathway. p16 (CDKN2A) is a known melanoma susceptibility gene. Here, we use retrovirally mediated gene transfer to confirm that the normal form of senescence in cultured human melanocytes involves p16, since disruption of the p16/retinoblastoma pathway is required as well as telomerase activation for immortalisation. Expression (immunostaining) patterns of senescence mediators and markers in melanocytic lesions provide strong evidence that cell senescence occurs in benign melanocytic naevi (moles) in vivo and does not involve p53 or p21 upregulation, although p16 is widely expressed. In comparison, dysplastic naevi and early (radial growth-phase, RGP) melanomas show less p16 and some p53 and p21 immunostaining. All RGP melanomas expressed p21, suggesting areas of p53-mediated senescence, while most areas of advanced (vertical growth-phase) melanomas lacked both p16 and p21, implying escape from both forms of senescence (immortalisation). Moreover, nuclear p16 but not p21 expression can be induced in human melanocytes by oncogenic BRAF, as found in around 80% of naevi. We conclude that cell senescence can form a barrier to melanoma development. This also provides a potential explanation of why p16 is a melanoma suppressor gene.