Sonographic appearance of mucinous carcinoma of the breast

The aim of this study was to evaluate the sonographic and mammographic features of mucinous carcinoma and to correlate the imaging features with two histologic classifications.

Two radiologists analyzed the mammographic and sonographic features of 33 mucinous carcinomas. Mammographic features according to the Breast Imaging Reporting and Data System (BI-RADS) and sonographic features were recorded and analyzed. The imaging features of the mass were correlated with the nuclear grade and mucin content of these 33 mucinous carcinomas. The incidence of axillary lymph nodes metastasis in different histologic grades and their detection by imaging were also assessed.

As many as 21.2% (7/33) of mucinous carcinomas could not be detected mammographically. When they were detected mammographically, more than 92% of the tumors presented as a mass, either oval or lobular. Microlobulations were present in 38.5% of these lesions. The margin of the lesion as seen on mammography can be used to predict the histologic grade. A circumscribed margin was associated with a favorable histologic grade (p = 0.01), whereas an indistinct margin was more commonly associated with the mixed type of lesion (p = 0.05). Sonographically, mixed cystic and solid components, distal enhancement, and microlobulated margins were commonly found in mucinous carcinomas, with an incidence of 37.5%, 43.8%, and 56.3%, respectively. Homogeneity on sonography was associated with the pure type of mucinous carcinoma and hence a better prognosis. Sonography showed a sensitivity of 50%, specificity of 89%, positive predictive value of 60%, negative predictive value of 84%, and accuracy of 79.2% in the detection of axillary lymph node metastasis.

Both sonographic and mammographic assessments are important in the correct diagnosis of mucinous carcinoma, the prediction of histologic grade, and the prognosis of the tumors.