The purpose of this study was to describe the mammographic and sonographic appearances and the clinical-pathologic features of invasive micropapillary carcinoma.

Between December 1999 and March 2005, among the 3,109 patients who underwent operation for breast cancer, 25 patients proved to have invasive micropaillary carcinoma. Among the 25 patients, we included 22 patients (mean age: 48, range: 26-77 years) who had undergone preoperative mammography and ultrasound. The mammographic and sonographic findings of the lesions were analyzed retrospectively. The pathologic findings were analyzed via the clinical records and pathology reports.

Patients manifested with a palpable mass (77%, 17/22), bloody nipple discharge (14%, 3/22) or incidental lesion on the screening mammography (9%, 2/22). On mammography, a mass with an irregular (86%, 12/14) shape and an indistinct (43%, 6/14) or spiculated (43%, 6/14) margin was the most common findings on mammography. On sonography, a hypoechoic (91%, 20/22) mass with irregular shape (73%, 16/22) and an indistinct (32%, 7/22) or microlobulated (32%, 7/22) margin was the most common finding. Pathologically, axillary lymph node metastasis was present in 73% (16/22) of the patients.

Invasive micropapillary carcinoma appeared an irregular shaped mass with an indistinct margin mass or microcalcifications on mammography and/or sonography. The tumors were frequently associated with axillary lymph node metastasis.