IS Case 241: Invasive lobular carcinoma
Imaging Sciences URMC 2008
Publication Date: 2009-05-26
Invasive lobular carcinoma (ILC) accounts for 5% to 15% of breast cancers. Its overall prognosis is thought to be similar to that of the invasive ductal subtype. Histologically, lobular carcinomas demonstrate a pattern of infiltrating tumor cells, often in a single file pattern, or in loose clusters or sheets. Most cases present as a palpable mass or mammographic density, but about one-fourth of cases have a diffuse pattern of invasion and may produce only vague skin thickening and subtle architectural distortion on mammography.
Many reports suggest that lobular carcinomas have a greater incidence of bilaterality. However, the actual incidence is closer to 5% - 10%, similar to ductal carcinomas. Lobular carcinomas metastasize in a different pattern than other breast cancers, with metastases to the peritoneum, leptomeninges, gastrointestinal tract, and ovaries and uterus more frequently seen. They are less likely to metastasize to the lungs and pleura.
Mammographic detection of ILC may be difficult, which may be due the diffuse infiltrative pattern of single rows of malignant cells, which causes little distortion of the underlying anatomic structures, and little reaction of the adjacent connective tissue. As such, subtle mammographic findings such as asymmetric density and architectural distortion have been reported. They are often only seen on one view, most commonly the craniocaudal view. Microcalcifications are uncommon with ILC, and are frequently unrelated.
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