Mammographic, sonographic and MR imaging features of invasive micropapillary breast cancer

Describe mammographic, sonographic and MRI findings of invasive micropapillary carcinoma (IMPC) of the breast.

Review of the pathology database identified 43 patients (mean age, 59.3 years) with the diagnosis of breast IMPC. Three patients had no available imaging studies. Mammograms (40), breast ultrasounds (33) and MRIs (8) were retrospectively evaluated by two radiologists in consensus following the BI-RADS Lexicon. Clinical, histopathologic features, as well as hormone status were recorded.

Twenty patients presented with palpable abnormality (20/40, 50%). Thirty-five patients had an abnormal mammogram (87.5%, 35/40) showing 39 lesions, 29 corresponding to masses (29/39, 74.4%), 11 associated with microcalcifications and two associated with architectural distortion. Sonography identified 41 masses (in 33 patients) displaying an irregular shape (30/41, 73.2%), appearing hypoechoic (39/41, 95%), with spiculated or angular margins (26/41, 63.4%), non-parallel orientation (26/41, 63.4%) and combined acoustic posterior pattern (18/41, 44%). MRI identified 13 lesions (in eight patients), 12 as masses (12/13, 92.3%) with irregular or spiculated margins (12/12, 100%), eight displaying an irregular or lobulated shape (8/12, 66.7%), six with homogeneous internal enhancement (6/12, 50%) and eight with type 3 enhancement curve (8/12, 61.5%). Associated non-mass like enhancement was noted in two patients. Twenty-nine patients had associated lymphovascular invasion (29/40, 72.5%) and axillary lymph node metastases were present in 22 of the 39 patients (22/39, 56%).

Invasive ductal carcinoma with IMPC features display imaging findings highly suspicious of malignant lesions. They are associated with high lymphovascular invasion and lymph node metastases rates.