Abstract
Primary skin cancers comprise most malignant lesions of the skin but secondary metastases from internal malignancies remain often overlooked; Studies show the prevalence of skin metastases is about prevalence of 1% to 4.3% and usually present as single or multiple nodules with firm consistency and flesh- or red-pink coloration. Metastatic skin cancers with breast origin can involve chest, head and neck, abdomen, back, buttock and surgical scars. Generally, skin metastasis is a sign of poor prognosis. Addressing the underlying primary malignancy is the most important therapeutic approach. The patient is a 72-year-old female who presented with a scalp nodule. She has no previous history of malignancies. Physical examination reveals a 1.4cm pink nodule with large surface telangiectasia on the left anterior vertex scalp. The biopsy from the nodule revealed unremarkable epidermis, and a papillary tumor within the dermis extending to the edge of the biopsy. The tumor is composed of branching papillae lined by medium-sized tumor cells with eosinophilic cytoplasm and stratified nuclei. The nuclei show moderate atypia and increased mitotic activity. Lymphovascular tumor invasion and focal mucinous stroma is present. The histologic appearance is consistent with metastatic papillary carcinoma. The immunostaining results of tumor cells are as follows: Positive: CK7, RCC, P504S, CEA, EMA, ER and PR. Rare focal positivity: GCDFP-15, breast cocktail. Negative: p63, CK5/6 (excludes primary cutaneous adnexal tumors), CD10, PAX8, CK20, CDX2, TTF-1 and thyroglobulin. The molecular cancer classifier (cancer ID results) result shows breast adenocarcinoma with the probability of 96%.
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