Abstract
Background: Cutaneous adnexal tumor arising from the skin (sebaceous, pilar, eccrine, follicular, and endocrine) usually presents as a solitary dermal nodule. Histologic and positive breast immunohistochemichal markers (GCDF-15, ER, PR, GATA-3 and mammaglobin) makes distinction of primary cutaneous adnexal carcinoma versus breast metastasis difficult. In rare instances, they may present as a breast mass and can mimic breast carcinoma clinically and radiologically, causing diagnostic dilemmas for the treating physician and pathologist. Method: We used cbioportal GENIE v9.0-public database, a multi-institutional web-based platform that curates data on cancer genomics from prior literature as well as The Cancer Genome Atlas database, to compare alterations in each individual gene from malignant adnexal tumors and breast cancer database. Cbioportal main studies on skin cancer, non-melanoma included 53 malignant adnexal tumors before February 2021, including: (Sweat Gland Carcinoma/Apocrine Eccrine Carcinoma, Endocrine Mucin Producing Sweat Gland Carcinoma, Sweat Gland Adenocarcinoma and Porocarcinoma/Spiroadenocarcinoma). We compared the mutational data of these samples with breast cancers (11727 samples) in the database. Results: Among the skin adnexal cancers 229 somatic mutations, 31 copy alteration and 4 fusions were found. We selected genes with highly significant difference between malignant adnexal tumor and breast cancer gene alterations (p-value<10-7). We identified 4 signature genes (PIK3CA, TCF7L1,CTNNB1 and EPHA5 )(table 1). Conclusion: The 4 signature genes identified in this study can be used to differentiate breast versus skin adnexal cancer of unknown primary.Financial Disclosure: No current or relevant financial relationships exist.