Primary and metastatic lobular carcinoma of the breast.

Invasive lobular carcinoma of the breast is the second most common type of primary breast cancer, accounting for 8-14% of cases, but is often difficult to diagnose early. It typically shows a diffuse pattern of infiltration within the breast, resulting in a variety of often subtle radiological appearances. A similar infiltrative pattern is seen in its metastatic form, with involvement of the gastrointestinal tract, peritoneum, retroperitoneum, bone marrow, meninges and uterus occurring more frequently than with the more common infiltrating ductal carcinoma of the breast. This pictorial essay illustrates the spectrum of radiological appearances which may be encountered with both primary and secondary lobular carcinoma.