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In most cases, cutaneous metastases develop after the diagnosis of the primary internal malignancy has been established, but sometimes they can be discovered earlier or simultaneously. We describe a case of a 90-year-old woman who presented to the emergency room in poor general condition, with cutaneous lesions characterized by hot, infiltrated, violaceous and erythematous plaques involving the left chest wall. The clinical and histopathological findings were consistent with the recently described variant of inflammatory cutaneous metastatic carcinoma named carcinoma hemorrhagiectoides. Microscopic examination demonstrated extensive infiltration of the dermis by tumor cells as well as intralymphatic involvement by neoplastic cells. This is a very rare presentation of cutaneous metastasis from breast cancer.

Background Merkel cell carcinoma (MCC) is an aggressive malignant neuroendocrine tumour. There are two subsets of MCC, one related to Merkel cell polyomavirus (MCPyV) and the other to ultraviolet radiation (UVR). MCPyV-positive and MCPyV-negative MCCs have been considered to be different tumours, as the former harbour few DNA mutations and are not related to UVR, and the latter usually arise in sun-exposed areas and may be found in conjunction with other keratinocytic tumours, mostly squamous cell carcinomas. Two viral oncoproteins, large T antigen (LT; coded by MCPyV_gp3) and small T antigen (sT; coded by MCPyV_gp4), promote different carcinogenic pathways. Objectives To determine which genes are differentially expressed in MCPyV-positive and MCPyV-negative MCC; to describe the mutational burden and the most frequently mutated genes in both MCC subtypes; and to identify the clinical and molecular factors that may be related to patient survival. Methods Ninety-two patients with a diagnosis of MCC were identified from the medical databases of participating centres. To study gene expression, a customized panel of 172 genes was developed. Gene expression profiling was performed with nCounter technology. For mutational studies, a customized panel of 26 genes was designed. Somatic single nucleotide variants (SNVs) were identified following the GATK Best Practices workflow for somatic mutations. Results The expression of LT enabled the series to be divided into two groups (LT positive, n = 55; LT negative, n = 37). Genes differentially expressed in LT- negative patients were related to epithelial differentiation, especially SOX9 , or proliferation and the cell cycle (MYC , CDK6), among others. Congruently, LT displayed lower expression in SOX9 -positive patients, and differentially expressed genes in SOX9 -positive patients were related to epithelial/squamous differentiation. In LT -positive patients, the mean SNV frequency was 4.3; in LT -negative patients it was 10 (P = 0.03). On multivariate survival analysis, the expression of SNAI1 [hazard ratio (HR) 1.046, 95% confidence interval (CI) 1.007–1.086; P = 0.02] and CDK6 (HR 1.049, 95% CI 1.020–1.080; P = 0.001) were identified as risk factors. Conclusions Tumours with weak LT expression tend to co-express genes related to squamous differentiation and the cell cycle, and to have a higher mutational burden. These findings are congruent with those of earlier studies. [ABSTRACT FROM AUTHOR]