Merkel cell carcinoma (MCC) is a rare but very aggressive human malignancy of the elderly or immunosuppressed patients. Recently, the clonal integration of a new human polyoma virus, which was termed Merkel cell polyomavirus (MCPyV), has been reported in 8 of 10 MCC patients. In the present study, we studied the formalin-fixed and paraffinembedded tissue specimens of 39 MCC for the presence of MCPyV by PCR. We applied four different primer sets directed against the large T antigen and the VP1 gene of MCPyV. We were able to detect MCPyV in 77% (n = 30) of MCC as confirmed by sequence analyses of the PCR products. Sequence analyses showed only minor nucleotide changes compared with the previously published MCC sequences. In addition, one patient revealed the amplification of two PCR products using PCR primers directed against the VP1 gene. Sequence analyses confirmed the presence of the expected 351-bp PCR product and in addition a second PCR product of 261 bp containing a unique 90-bp deletion in the VP1 gene, which will lead to a predicted loss of 28 amino acids. The unique 90-bp deletion within the VP1 gene possibly is a result of incomplete viral integration of MCPyV in the MCC. The presence of MCPyV in the majority of MCC tissue specimens in our study strongly underlines a possible role for MCPyV as an etiologic agent in the carcinogenesis of MCC. [Cancer Res 2008;68(13):5009-13]

Recently, a new human polyoma virus has been identified in Merkel cell carcinomas (MCC). MCC is a highly aggressive neuroendocrine nonmelanoma skin cancer (NMSC) associated with immunosuppression. Clonal integration of this virus which was termed Merkel cell polyoma virus (MCPyV) was reported in a number of MCC. Squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) are also NMSC and are the most frequent cancers in the setting of immunosuppression. A unique group of 56 NMSC from 11 immunosuppressed patients and 147 NMSC of 125 immunocompetent patients was tested for MCPyV by DNA PCR, targeting the Large T Antigen and the structural Viral Protein 1. NMSC included SCC, BCC and Bowen's disease (BD). In addition, normal skin and 89 colorectal cancers were tested. MCPyV specific sequences were significantly more frequently found in NMSC of immunosuppressed patients compared to immunocompetent patients (p < 0.001). In particular BD and BCC revealed a significant increased association of MCPyV of immunosuppressed patients (p 5 0.002 and p 5 0.006). Forty-seven of 147 (32%) sporadic NMSC were MCPyV positive. Interestingly, 37.5% (36/96) of sporadic BCC of immunocompetent patients were MCPyV positive. No MCPyV was detected within normal skin and only 3 out of 89 of additionally tested colorectal cancers were MCPyV positive. Our data show that MCPyV is a frequently reactivated virus in immunocompromized patients. How MCPyV contributes to the pathogenesis of NMSC, i.e., BD, SCC and BCC, in immunosuppressed patients and in addition, potentially to the pathogenesis of a subset of sporadic BCC needs further investigations. ' UICCKey words: nonmelanoma skin cancer (NMSC); merkel cell polyoma virus (MCPyV); immunosuppression Squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) are nonmelanoma skin cancers (NMSC) and in this order constitute the most frequent cancers associated with immunosuppression in transplant recipients. [1][2][3][4][5][6] According to the steadily increasing number of transplant operations performed each year in the European Union and the United States, post-transplant skin cancer is a leading medical issue in current transplantation medicine. To date a number of risk factors for the increasing number of NMSC under immunosuppression have been identified. 2 In addition to SCC and BCC, other NMSC, i.e., sebaceous cancers, cutaneous lymphomas and Merkel cell carcinomas (MCC) occur more frequently in post-transplant patients. 7,8 MCC has been described relatively recently and is a rare but very aggressive malignant neuroendocrine skin cancer of the elderly and immunosuppressed. [8][9][10] Very recently, Feng et al. reported the identification of a new human polyoma virus which was designated Merkel cell polyomavirus (MCPyV) based on its detection in MCC by digital transcriptome subtraction technique. 11 They reported the presence of MCPyV in 8 of 10 human MCC and also clonal integration of the viral DNA in 6 of 8 MCPyV-positive MCC. Analyzing the first large number patient cohort of MCC by PCR...

Background: Multiple studies have compared the performance of artificial intelligence (AI)ebased models for automated skin cancer classification to human experts, thus setting the cornerstone for a successful translation of AI-based tools into clinicopathological practice.

In the past decades, the incidence of melanoma has been reported to rise in epidemic proportions. The chief reason for that pseudo-epidemic is improved criteria for diagnosis that allow melanomas to be recognized far more accurately and at earlier stages. The rising number of melanomas diagnosed has resulted in increased diagnostic scrutiny, more pigmented lesions being biopsied and more melanomas recognized, thus enhancing the 'epidemic' in self-perpetuating fashion. Regression of melanomas may, in part, explain why lesions undetected before did not result in a far higher mortality. Another potential reason for the disparity between increasing incidence of melanoma and relatively steady mortality may be overdiagnosis of melanoma. The latter may be curtailed by establishment of well-defined diagnostic categories, efforts to establish reliable criteria for recognition of those categories, better clinicopathologic correlation, postponement of biopsy of pigmented lesions in the case of irritation and excisional rather than incisional biopsies.

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Drug eruptions are among the most common inflammatory diseases of the skin and also among those biopsied most often. Yet, the value of histopathologic examination of drug eruptions has often been disputed. One reason is that the spectrum of histopathologic changes in drug eruptions is broad. Nevertheless, each histopathologic pattern assumed by drug eruptions has a limited number of differential diagnoses, and numerous criteria and clues are available to distinguish drug eruptions from other diseases associated with those patterns. By recognition of common patterns, consideration of differential diagnoses, and attention to distinct clues, a histopathologic diagnosis of drug eruption can usually be made with confidence.

SCC of the hair follicle represents a poorly recognized but distinctive subset of SCC of the skin that should be considered in the differential diagnosis of other cutaneous epithelial tumors. The term follicular SCC (FSCC) is proposed for this neoplasm.

Our cases provide additional evidence supporting the benign nature of this atypical vascular proliferation, not recurring, never developing metastases and being cured readily by local excision. Clinical, histopathological and ultrastructural findings suggest a lymphatic origin. Whether these lesions represent a neoplastic or a reactive condition secondary to radiotherapy is unclear. The name 'benign lymphangiomatous papules of the skin following radiotherapy' is proposed.