Primary acinic cell carcinoma of the breast is associated with a poor outcome: A case report and literature review.

Primary acinic cell carcinoma (AcCC) is a rare histological type of malignant breast cancer. AcCC was first identified as an entity in 1996, and since then 51 cases have been reported in the literature. The first early case reports and reviews suggested a relatively favourable prognosis for patients with AcCC; however, reports of AcCC recurrent disease have been more recently described in a subset of patients with high-grade disease. The present case report describes an unusual case of estrogen receptor-negative AcCC of the breast in a 59-year-old woman who did not respond to neoadjuvant chemotherapy (NACT), despite imaging revealing a large reduction in tumour volume. Furthermore, 14 months after NACT completion, the patient presented with disease progression comprising peritoneal involvement and linitis plastica. The patient started on first-line chemotherapy with carboplatin and paclitaxel combination, achieving a notable and prolonged response. After 2.5 years and while still on carboplatin and paclitaxel, the patient developed leptomeningeal carcinomatosis disease (LD) and died 6 weeks after LD presentation. The present report is the third case of AcCC in which cancer-associated death was registered. As studies on large series are lacking, further investigations are required to identify predictors of poor outcome. Notably, the prolonged response achieved to first-line chemotherapy suggested that platinum and taxane compounds may offer a potential therapeutic benefit for patients with AcCC. Moreover, the present case report highlights the importance of careful interpretation of follow-up imaging, as an apparent positive response to treatment may not always be a true representation of disease.