Solid Variant of Adenoid Cystic Carcinoma of the Breast: A Case Series With Proposal of a New Grading System.

Adenoid cystic carcinoma (ACC) of the breast is a low-grade malignancy “triple negative” breast tumor. ACC of the breast can present a great variety of morphological features having a prognostic impact. Recently, cases of ACC having solid-basaloid features (SBACC) have been described. In the present study, 6 cases of SBACC have been reported. All the cases affected female patients aged 47 to 69 years (mean = 54 years). Two patients had metastases to the axillary lymph nodes, and 2 patients experienced local recurrences. No deaths due to the tumor were observed. A review of the literature on breast SBACC showed that local recurrences and lymph node metastases are more frequent than in the ACC conventional type; nevertheless, no deaths due to the tumor are registered at the moment. On the contrary, cases of ACC with features of malignant transformation are on record. Therefore, a new grading system on breast ACC is proposed.