Michael Tronnier

Uv-irradiated Melanocytic Nevi Simulating Melanoma In Situ

A causative role of UV light in the development of melanocytic neoplasms has often been suggested. In order to investigate the short-term effects of UV light on melanocytic nevi. the morphological and immunohistochemical changes in nevi after a single UV irradiation are studied in 12 nevi from 10 patients and compared with the nonirradiated part of the same nevus. After irradiation more melanocytes above the dermal-epidermal junction are observed in seven nevi. simulating a melanoma in situ in three nevi. Moreover, a marked increase in the expression of HMB-45 is found after irradiation in all investigated nevi, indicating an activation of the melanocytes and active melanosome formation. The metabolic activity correlates with the ultrastructural findings, which show a large cytoplasm, hypertrophic Golgi apparatus, abundant mitochondria, and an increased number of mclanosomes of different stages. One week after irradiation, no increase in the proliferative activity of the melanocytes is found. The morphological and immunohistochemical changes after one low dose of UV irradiation should be considered in the differential diagnosis of pigmented skin lesions. The UV-irradiated nevus should be added to the list of so-called simulators of malignant melanoma.

Cadherin expression pattern in melanocytic tumors more likely depends on the melanocyte environment than on tumor cell progression

Background:  Adhesion molecules have been assigned an important role in melanocytic tumor progression. By the loss of E‐cadherin, melanocytes might escape the control of neighbouring keratinocytes. Although in vitro data support this hypothesis, there are yet no conclusive immunohistochemical results on cadherin expression in melanocytic tumors.

Enhanced expression of Ki-67, topoisomerase IIα, PCNA, p53 and p21WAF1/Cip1 reflecting proliferation and repair activity in UV-irradiated melanocytic nevi

To investigate the effect of ultraviolet (UV) irradiation on the expression of cell cycle-associated proteins, melanocytic nevi from healthy volunteers were partially covered, irradiated with a defined UV dose, and excised 1 week thereafter. The irradiated and the protected parts were examined separately by conventional microscopy and immunohistochemistry using the antibodies Ki-S11 (Ki-67), Ki-S7 (topoisomerase IIalpha), PC10 (proliferating cell nuclear antigen [PCNA]), DO-7 (p53), 6B6 (p21WAF1/Cip1), and the melanocytic marker HMB-45. DNA nick-end labeling was used as a marker of apoptosis. Irradiation resulted in morphological changes and increased HMB-45 reactivity. Proliferation, as assessed by Ki-67 and topoisomerase IIalpha expression, was also clearly enhanced in the UV-exposed areas. This was confirmed by the appearance of occasional mitotic figures. PCNA expression levels markedly exceeded those of the proliferation markers and did not correlate with the latter in most cases. p21 immunolabeling indices were also consistently augmented after UV exposure; hence it is likely that growth-inhibitory mechanisms partly compensate for the proliferative impulse, and the disproportional rise in PCNA expression probably reflects DNA repair activity. Enhanced p53 immunostaining in four cases suggests that the induction of p21 after irradiation may be p53 mediated, whereas no concomitant apoptotic events were observed. We conclude that UV light can stimulate the proliferative activity of melanocytes in melanocytic nevi, but that simultaneously cell cycle inhibitors are activated to permit DNA repair.

Adhesion molecule expression in normal skin and melanocytic lesions. Role of UV-irradiation and architectural characteristics in nevi.

Cell adhesion between surfaces of cells and to extracellular matrices represents a fundamental mechanism in tissue organization and influences the biological behaviour and the architecture of tumors. We investigated the expression of various adhesion molecules in normal skin (n=5), nevi (n=29), and malignant melanoma (n=10) by immunohistochemistry. Special attention was paid to the correlation between adhesion molecule expression and the respective architectural features, e.g. UV‐induced morphological changes, and the arrangement of melanocytes in congenital nevi. In nevi, a single erythemagenic close of UV‐light did not influence the influence expression of melanocytes, but results in an upregulation of α3β1‐ and α6β1‐integrin within the suprabasal layers of the epidermis. This suprabasal labelling was associated with an increased number of suprabasal melanocytes in UV‐irradiated nevi which were detected with HMB‐45 antibody. Nine of 10 congenital nevi demonstrated a labelling of α4β1‐integrin only in melanocytes of the deeper dermis. This integrin previously has been associated with high tumor thickness and the clinical outcome in melanomas. The integrin profile observed in melanomas differed in part from that seen in nevi with expression of β2‐and β3‐integrins in some cases. The results may indicate a correlation between adhesion molecule expression and histopathological findings in melanocytic lesions.

One single erythemagenic UV irradiation is more effective in increasing the proliferative activity of melanocytes in melanocytic naevi compared with fractionally applied high doses

The effect of a single irradiation with UV light on the expression of Ki67 antigen, topoisomerase IIα, proliferating cell nuclear antigen (PCNA), the melanocyte activation marker HMB‐45 and protein p53 in melanocytic naevi was investigated 1 week after application of a single erythemagenic UV dose and after daily exposures with suberythemagenic doses over 4–6 weeks. To assess the effect of UV irradiation, one half of each naevus was shielded with black tape during the UV exposure, and the irradiated part and the non‐irradiated parts were evaluated separately. Except for HMB‐45, a double staining procedure was performed to distinguish between labelled melanocytes and keratinocytes. After semiquantitative assessment of the staining signal the irradiated part was compared with the non‐irradiated part of the same naevus. Morphological changes and an enhanced proliferative/reparative activity in melanocytes were much more frequent in the naevi irradiated with a single erythemagenic UV dose than in those given repeated suberythemagenic doses. In addition, the keratinocytes showed an increased labelling for PCNA and p53 after the single irradiation. These data may support the importance of intermittent UV exposure and sunburns in the development of both benign and malignant melanocytic lesions.

Attachment and chemotaxis of melanocytes after ultraviolet irradiation in vitro.

Because ultraviolet (UV) radiation is able to influence the spatial distribution of melanocytes in melanocytic naevi in vivo, we investigated the influence of UV radiation on the ability of melanocytes to adhere to the extracellular matrix proteins fibronectin, laminin and collagen type IV in vitro. In addition, chemotaxis of melanocytes was studied using both fibronectin and the supernatants from irradiated, as well as non‐irradiated, keratinocytes and fibroblasts as attractants. Melanocyte attachment to fibronectin was significantly increased 48 h after a single UV irradiation at 30 mJ/cm2 in comparison with that of non‐irradiated melanocytes, whereas attachment to laminin and collagen type IV showed only minor changes after UV exposure. The UV‐induced increase in attachment to fibronectin was suppressed by preincubation with antibodies against α5β1 or αvβ3 integrin. Both immunohistochemistry and flow cytometric analysis showed an increase in α5β1 integrin expression on melanocytes after UV exposure. The chemotaxis of melanocytes to fibronectin was not influenced by UV exposure. A decreasing migration rate of melanocytes towards the supernatants of UVA‐irradiated fibroblasts was observed with increasing UVA doses. The chemotactic effects of conditioned medium of keratinocytes towards melanocytes was not influenced either by UVB or by UVA. The results indicate that UV radiation may alter the ability of melanocytes to adhere to certain substrates by modification of integrin expression. Because fibronectin, as the major target protein of UV‐altered attachment, is located in the dermis, the UV‐induced morphological changes in melanocytic lesions, with an increase in suprabasally located melanocytes within the epidermis, may be due to other changes in the adhesive properties of melanocytes.

MMP-2, TIMP-2 and MT1-MMP are differentially expressed in lesional skin of melanocytic nevi and their expression is modulated by UVB-light

Background:  In malignant melanoma, recent studies have demonstrated an important role of matrix‐metalloproteinase 2 (MMP‐2), its co‐activating enzyme membrane‐type matrix‐metalloproteinase 1 (MT1‐MMP), and the endogenous inhibitor of MMP‐2, tissue‐inhibitor of matrix metalloproteinase 2 (TIMP‐2). Melanocytic nevi are benign neoplasms of the melanocytic lineage, but may exhibit dysplastic features that can be difficult to distinguish from early stage melanoma. As shown in earlier studies, nevi show important morphological and phenotypical changes in response to ultraviolet light (UVB) irradiation.

Histopathological diagnostics of malignant melanoma in accordance with the recent AJCC classification 2009: Review of the literature and recommendations for general practice

Background: TNM classifications are the basis for diagnostic and therapeutic procedures in oncology. Histopathological reports have to enable a proper indexing of tumor specific findings into recent classifications.

Detection of Merkel cell polyomavirus and human papillomaviruses in Merkel cell carcinoma combined with squamous cell carcinoma in immunocompetent European patients.

Background: About 10% of patients with Merkel cell carcinoma (MCC) suffer from an associated squamous cell carcinoma (SCC). In European patients, Merkel cell polyomavirus (MCPyV) is detectable in 60%–88% of the MCC tumors. In combined lesions, MCPyV was not detectable so far. Methods: We investigated 2 combined tumors of MCC and SCC for the presence of MCPyV and human papillomavirus (HPV) by polymerase chain reaction and immunohistochemistry. Results: In both lesions, MCPyV DNA was found, and in 1 case, HPV DNA was also detected. This is the first report of a coinfection with HPV and MCPyV in combined MCC–SCC tumors. Conclusions: The results underline the hypothesis of cocancerogenesis of 2 oncogenic viruses in nonmelanoma skin cancer. Technical reasons and a low viral copy number of MCPyV hampering immunohistochemical detection may be responsible for the negative results in the literature.

Treating advanced melanoma: current insights and opportunities

Whereas thin melanomas have an excellent prognosis after sufficient surgical treatment, melanoma disease in advanced stages is still a therapeutic challenge. After decades of frustrating studies, new therapeutic strategies have come up in the past few years. On the one hand, increasing insights into the molecular aberrations in melanoma have led to specific “targeted” therapies to affect only the mutated tumor cells, as in many other types of cancers. Today there are few “targeted” substances which are already approved and successfully used for single or combination therapy, but many others are under development. While on the other hand, nonpersonalized strategy substances have been developed successfully inducing an immunologic tumor response. Both kinds of therapy have been found to result in an improvement not only of the response rate, but also of the overall survival in metastatic disease, which represents a milestone in melanoma therapy. However, using these therapies there is still much to learn regarding the effects, the side effects, and the limitations of these promising substances.