PET/CT underestimates locoregional lymph node staging in large primary breast cancer patients. PET/CT is a valuable tool to discard unsuspected extra-axillary lymph nodes and distant metastases.

Metaplastic carcinoma of the breast shows high signal intensity on T2-weighted MRI. This finding is related to the necrotic component of the tumor and may be useful for preoperative diagnosis of metaplastic carcinoma of the breast, although it must be differentiated from mucinous carcinoma and, less frequently, necrotic infiltrating ductal carcinoma.

A denoidcysticcarcinomais a rarevariant of adenocarcinoma that usually occursinthemajorand minor salivary glands. Nevertheless, tumors with this patternhavebeenobservedin other organs including the breast, tracheobronchial tree, uterine cervix, larynx, and Bartholin's gland[ 1â€"5]. The cell of origin is obscure, but evidence suggests that it may be derived from the ductal epithelium and myoepithe hum [6]. Pathologically, the presenceof both cell types is necessary for the diagnosis of adenoidcysticcarcinomaof the breast.Adenoid cystic carcinoma of the breast constitutes lessthan 1% of all mammarycar cinomas. This unusual neoplasm of the breast has certain histopathologicand bio logic characteristics that distinguish it from more common histologic types. For example, the incidence of axillary lymph node in volvement is lower and distant metastases are uncommon, although they can occur without prior lymph nodeinvolvement.This lack of prognostic significance for negative axillary lymph nodes suggests that axillary dissectioncan be eliminatedfrom the surgi cal treatment of low-grade adenoid cystic carcinoma and that wide excision alone couldbe curativein thosecases[6]. The mammographic features of these le sions have scarcely been reported in the liter ature to our knowledge. We describe the clinical and mammographicfindingsand the histopathologic features of seven cases of proven adenoid cystic carcinoma. Materials and MethodsA retrospective review of all cases of pathologi cally proven adenoid cystic carcinoma of the breast between 1988and 1996 was undertakenat our de partment. During this 8-year period. a total of 1015 invasivebreast tumors were diagnosed:sevencases of adenoid cysticcarcinoma of thebreast werein cluded in the study. Clinical histories, mammo grams, and cytologic and histologic studies of these patients were reviewed. Women were from 40 to 79 years old (mean age. 60 years old).All patients underwent conventional X-ray mam mography. Standard craniocaudal and mediolateral oblique views of each breast were obtained.

Purpose To investigate the performance of tumor subtype and various magnetic resonance (MR) imaging parameters in the assessment of tumor response to neoadjuvant systemic therapy (NST) in patients with breast cancer and to outline a model of pathologic response, considering pathologic complete response (pCR) as the complete absence of any residual invasive cancer or ductal carcinoma in situ (DCIS). Materials and Methods This was an institutional review board-approved retrospective study, with waiver of the need to obtain informed consent. From November 2009 to December 2014, 111 patients with histopathologically confirmed invasive breast cancer who were undergoing NST were included (mean age, 54 years; range, 27-84 years). Breast MR imaging was performed before and after treatment. Presence of late enhancement was assessed. Apparent diffusion coefficients (ADCs) were obtained by using two different methods. ADC ratio (mean posttreatment ADC/mean pretreatment ADC) was calculated. pCR was defined as absence of any residual invasive cancer or DCIS. Multivariate regression analysis and receiver operating characteristic analysis were performed. Results According to their immunohistochemical (IHC) profile, tumors were classified as human epidermal growth factor receptor 2 (HER2) positive (n = 51), estrogen receptor (ER) positive/HER2 negative (n = 40), and triple negative (n = 20). pCR was achieved in 19% (21 of 111) of cases; 86% of them were triple-negative or HER2-positive subtypes. Absence of late enhancement at posttreatment MR imaging was significantly associated with pCR (area under the curve [AUC], 0.85). Mean ADC ratio significantly increased when pCR was achieved (P < .001). A κ value of 0.479 was found for late enhancement (P < .001), and the intraclass correlation coefficient for ADCs was 0.788 (P < .001). Good correlation of ADCs obtained with the single-value method and those obtained with the mean-value methods was observed. The model combining the IHC subtype, ADC ratio, and late enhancement had the highest association with pathologic response, achieving an AUC of 0.92 (95% confidence interval: 0.86, 0.97). Conclusion Triple-negative or HER2-positive tumors showing absence of late enhancement and high ADC ratio after NST are associated with pCR. RSNA, 2016 Online supplemental material is available for this article.