Purpose: Our aims were to study the incidence, age at diagnosis, familial aggregation of cancer, clinical presentation, delay/pitfalls in the diagnosis and overall survival of the different types of breast angiosarcomas Material and Methods: We investigated all breast angiosarcomas diagnosed in the area of Vigo (Galicia, Spain) during the period between January 1974 and December 2020. Results: Twelve patients (11 women and 1 man) with breast angiosarcoma were identified among a total of 5000

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... ignant neoplasms of the breast: 3 primary angiosarcomas and 9 secondary angiosarcomas (7 post-radiotherapy and 2 Stewart-Treves syndromes -associated with lymphedema). Globally, the 12 breast angiosarcomas represent 0.24% of all malignant breast cancers (BCs) in our healthcare area; that is to say, one breast angiosarcoma is diagnosed every 400 BCs. The mean age at diagnosis was 66.5 years (range: 28-91). We highlight the intense familial aggregation of cancer (present in almost all cases) but genetic studies have only been performed in two of them. All the primary angiosarcomas appeared as palpable nodules, while the secondary ones showed a more heterogeneous clinical picture (cutaneous oedema, hematomas, red-bluish macules or even as nodules). This non-specific clinical presentation caused errors and was one of the causes of the diagnostic delay. The mean interval between the diagnosis of BC and angiosarcoma was 106 months (SD 46). Angiosarcomas showed a very aggressive behaviour: 8 of the 12 patients died, and survival ranged from 3 months to 19 months after diagnosis, with high rates of local and distant progression. Conclusions: Breast angiosarcoma is a neoplasm with a very poor prognosis. Due to its rarity and its different forms of presentation, it represents a diagnostic challenge. We have observed an intense and striking familial aggregation of cancer that leads us to think that there is a genetic predisposition that plays an important role in the carcinogenesis of breast angiosarcomas. Investigating and clarifying this predisposition could have consequences in its prevention and in the treatment planning (eg radiotherapy) of patients with BC.