Prognosis: Mammary analogue secretory carcinoma (MASC) is currently regarded as a low-grade carcinoma with a generally favorable prognosis. It has a low risk of local recurrences (15%), lymph node metastases (20%) and distant metastases (5%). There have been case reports of transformation to a high-grade lesion marked by accelerated growth and poor outcome. Overall, mortality is seen in 6% to 13% of cases of MASC. The image shows a focus of MASC with solid growth pattern. The tumor cells have bland morphology with uniform round to oval vesicular nuclei and small nucleoli. The cytoplasm is pale eosinophilic and granular or vacuolated. High-grade cytologic features and increased mitotic activity are not present.