Round or ovoid cells with little cytoplasm in a single-file infiltrating pattern, sometimes concentrically giving a targetoid pattern
Mixed
40%
No dominant pattern
Solid
10%
Sheets of classical-appearing cells with little intervening stroma
Alveolar
5%
Aggregates of classical-appearing cells
Tubulolobular
5%
Cells form microtubules in >90% of tumor (smaller than in tubular carcinoma)
Pleomorphic
Classical-appearing but with pleomorphic cells. It may include signet-ring cells, or plasmacytoid cells (pictured) which have abundant cytoplasm and eccentric nuclei.
Invasive lobular carcinoma demonstrating a predominantly lobular growth pattern
Lobular breast cancer. Single file cells and cell nests.
ILC may be subtle on low magnification (left). Higher magnification (right) shows invasive growth pattern and vesicular nuclei with prominent nucleoli.
Prognosis
Overall, the five-year survival rate of invasive lobular carcinoma was approximately 85% in 2003.[9]
Diagnosis
On mammography, ILC shows spiculated mass with ill-defined margins that has similar or lower density than surrounding breast tissues. This happens only at 44–65% of the time. Architectural distortion on surrounding breast tissues is only seen in 10–34% of the cases. It can be reported as benign in 8–16% of the mammography cases.[10]
Ultrasound has 68–98% sensitivity of detecting ILC. ILC shows irregular or angular mass with hypoechoic or heterogenous internal echoes, ill-defined or spiculated margins, and posterior acoustic shadowing.[10]
Loss of E-cadherin is common in lobular carcinoma but is also seen in other breast cancers.[11]