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Merkel cell carcinoma (MCC) is an infrequent, aggressive cutaneous neoplasm, that typically affects the photodamaged skin of elderly individuals, and immunosuppressed patients. Because a subset of MCC is closely related to UV radiation, MCC can develop concurrently with other tumors, most commonly, as a combined tumor with squamous cell carcinoma (SCC). These combined tumors appear to represent a distinct disease process from pure MCC, as they are mostly Merkel cell polyomavirus (MCPyV) negative, and show a more aggressive behavior. We present two additional cases of combined MCC and SCC with nodal metastases, one of which was MCPyV positive. Two different subtypes of MCC have been proposed based on their origin: a true neuroendocrine carcinoma, that is MCPyV positive and has a dermal origin, and a UV-related SCC with neuroendocrine differentiation. This theory could explain why MCC can develop concurrently with SCC, and why these combined cases are generally MCPyV negative. However, it fails to explain the minority of combined MCC and SCC tumors that are MCPyV positive. Because both our patients had a history of chronic UV exposure, we hypothesize that UV radiation probably played a major role in the pathogenesis of these tumors, while MCPyV integration probably acted as an additional trigger., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: The plaque variant of trichoblastoma has been described as a solitary tumor with diffuse infiltration of the lower dermis and hypodermis, with poorly defined borders. Herein, we report a new variant of multiple centrofacial trichoblastoma., Object: To describe clinical and pathological features of a new multiple kind of plaque variant of centrofacial trichoblastoma., Methods: Case series of patients with a multiple-plaque variant of centrofacial trichoblastoma treated in our department between 2005 and 2017. We identified eight patients with the centrofacial plaque variant of trichoblastoma treated in our department from 2005 to 2017., Results: The final study sample comprised 13 trichoblastomas from four patients. All patients also developed at least one basal cell carcinoma. Mohs surgery was the method of treatment in the majority of the cases of trichoblastoma and in all the cases of basal cell carcinoma. We needed between 2 and 6 stages to obtain free margins in our cases of facial plaque trichoblastomas treated by Mohs surgery., Conclusion: To the best of our knowledge, a multiple-plaque variant of trichoblastoma has not been described in the literature. We suggest a genetic origin of this variant of trichoblastoma and describe its remarkable infiltrative nature, with poorly defined surgical margins., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Desmoplastic melanoma (DM) and cutaneous malignant peripheral nerve sheath tumors (MPNST) reveal histological and immunohistochemical similarities, including S100 positivity and negative staining for conventional melanocytic markers. We present 3 cases of cutaneous S100-positive spindle cell tumors in elderly patients, in which first findings led to initial misdiagnoses as cutaneous MPNST and benign peripheral sheath nerve tumor (neurofibroma). The identification of adjacent atypical melanocytic hyperplasia in the overlying skin along with tumor cell proliferation, also in the superficial dermis, the neurotropic component and the absence of any relationship between the tumor and a major nerve, pre-existing neural benign tumor or the existence of stigmata suggestive of neurofibromatosis raised consideration of a DM. Careful attention should be paid to the presence of a firm dermal nodule and atypical scar lesions especially in sun-exposed areas (mainly head and neck region) in elderly patients associated with S100-positive spindle cell proliferation, solar elastosis and adjacent atypical melanocytic proliferation. In such cases, the possibility of a DM should be excluded with caution, especially if the tumor reveals a paucicellular morphology resembling various non-melanocytic neoplasms including malignant or benign peripheral sheath nerve tumors., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Breast implant-associated anaplastic large cell lymphoma (ALCL) is a newly described clinical and pathologic entity that typically presents as seroma in the fibrous scar around the implant. Less frequently, it presents as a solid peri-implant mass, and there have been no reports to date of cutaneous lesions as the presenting manifestation. We report the case of a 56-year-old woman with a history of bilateral breast reconstruction following breast cancer of the right breast who consulted with several papules on the right breast suggestive of metastasis. Histopathology showed a proliferation of large epithelioid lymphocytes with highly pleomorphic cells and nuclei. The neoplastic cells were CD15 and CD30 positive and ALK-1 negative. The epithelial markers were all negative except for epithelial membrane antigen (EMA), which was weakly positive. Molecular analysis showed monoclonal T-cell receptor γ gene rearrangement, confirming a diagnosis of breast implant-associated ALCL. The non-specific morphology of the skin lesions, the epithelioid nature of the neoplastic cells and the expression of EMA can lead to an erroneous diagnosis of skin metastases from a poorly differentiated adenocarcinoma of the breast. We recommend immunohistochemical staining for CD30 and ALK-1 for patients with breast implants who develop anaplastic lesions., (© 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)