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High-grade carcinoma with a large central acellular zone (central acellular carcinoma, CAC) and matrixproducing carcinoma (MPC) are aggressive tumors that both have a central myxomatous acellular zone. Their characteristic morphology may be useful in diagnostic imaging. Ultrasonographic findings based on the Breast Imaging Recording and Data System (BI-RADS) and detailed histological features were evaluated in 11 cases of CAC and 2 cases of MPC to characterize their features. Safranin-O staining was undertaken for the evaluation of central acellular zones in these tumors. Overall, ultrasonography demonstrated heterogeneous hyperechoic lesions in the center of the hypoechoic mass. Posterior echo enhancement was observed in all but 1 case. One case was classified as malignant and the others as "borderline." Histologically, cancer tissue was located in the periphery of the tumor with a ring-like structure and fewer cellular central areas comprising hyaline cartilage myxoid material such as those stained by safranin-O. The present study showed that the pathological findings of CACs and MPCs accurately reflect the ultrasonographic findings. Tumors that showed hyperechoic areas in the center of the hypoechoic mass, with posterior echo enhancement indicating acellular zones composed by myxochondroid material, and that were also relatively round on ultrasonography may be benign, but evaluation is required to exclude CAC and MPC.

Fibroadenoma (FA) is a benign tumor that must be differentiated from carcinomas. FAs often exhibit myxedematous changes (myxomatous FA, M-FA). We previously reported on the clinical significance of M-FA. M-FA and (mucinous) carcinoma share clinical findings, rapid growth and a relatively large size, a high-depth/width (D/W) ratio, a relatively round shape, and posterior echo enhancement with internal hyperechogenicity on ultrasonography (US). Next, a biopsy is required for differential diagnosis. In this study, we evaluated the diagnostic significance of the cytological findings of M-FA with US findings. Among 13 FAs that were diagnosed by cytology, we compared (i) a group of six mucinous carcinomas with acellular mucin and a D/W ratio ≥ 0.7 (a suspicious factor for malignancy) with a group with a D/W ratio of <0.7, and (ii) the frequency of metachromasia on Giemsa stain between M-FAs and non-M-FAs among eight FA cases confirmed by histology. (i) FA lesions (7 of 13) showed metachromasia with Giemsa staining significantly more frequently than did mucinous carcinoma (0/6) (Fisher's exact test, P < 0.044). FA lesions with a D/W ratio ≥ 0.7 (6/7) showed metachromasia significantly more frequently than did FA with a D/W ratio <0.7 (1/6) (Fisher's exact test, P < 0.029). Among eight FA cases confirmed by histology, M-FA cases (6/6) demonstrated metachromasia significantly more frequently than non-M-FA cases (0/2) (P < 0.036). M-FA cytologically exhibits marked metachromasia on Giemsa staining. Combining cytological examination and understanding the clinical features of M-FA may allow us to choose cytological examination as a first-line diagnostic method for tumor-forming lesions.

The management of atypical intraductal lesions of the breast remains controversial. In the present study, the subsequent surgical excision results and follow-up data on 86 (3.65%) atypical intraductal lesions and 78 (3.31%) low-grade ductal carcinoma in situ (DCIS) from a cohort of 2358 needle biopsies were examined. There were 17 cases (0.72%) of pure flat epithelial atypia (FEA), 44 (1.87%) pure atypical ductal hyperplasia (ADH), three (0.13%) pure atypical lobular hyperplasia (ALH), 18 (0.76%) combined ADH + FEA, three (0.13%) combined ALH + FEA and one (0.04%) combined ALH + FEA + ADH. Subsequent surgical excisions were done in 53 cases and revealed the following incidences of malignancy: pure FEA (1/8); pure ADH (17/31); FEA + ADH (7/10); FEA + ALH (2/3); and FEA + ALH + ADH (0/1), with pure FEA showing significantly lower incidence of malignancy. In this cohort, there were 703 carcinomas including 155 DCIS with 78 cases (50.3%) being low-grade. FEA with ADH (and/or ALH) was present in 22 (28.2%) of these 78 cases of low-grade DCISs at surgical excisions. Pure FEA was not detected in any of the subsequently excised surgical materials of the atypical intraductal lesions nor the low-grade DCISs. Thus, pure FEA was very unusual in surgical specimens. When pure FEA is detected at needle biopsy, a wait and see approach can be adopted. However, when the FEA is associated with other concomitant atypical intraductal lesions, especially ADH, further excision should be contemplated.

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