Invasive lobular carcinoma of the breast

Dr Daniel J Bell and Radswiki et al.

Infiltrating or invasive lobular carcinoma (ILC) of the breast is the second most common type of invasive breast cancer after invasive ductal carcinoma (IDC) "not otherwise specified" (NOS).

They represent 5-10% of all breast cancer. The mean age at presentation may be higher than for IDC.

ILC is characterized microscopically by malignant monomorphic cells forming linear invasive columns that are loosely dispersed (note: IDC is more typically a discrete mass). Loss of E-cadherin has been demonstrated. ILC frequently invades the normal tissues without invoking the vigorous desmoplastic response that usually accompanies IDC. Cells of ILC often encircle ducts, thus preserving the architecture of the ducts. These histopathologic features limit mammography in detecting ILC.

The majority of ILCs have the following receptor profile 12:

  • estrogen receptor: positive
  • progesterone receptor: positive
  • HER2 amplification: negative

There is a greater rate of contralateral breast cancer in ILC compared with IDC with a 5-year rate of bilateral cancer of 8% (4% synchronous and 4% metachronous tumors).

ILC is more often multicentric and bilateral (10-15%). Therefore imaging evaluation of the contralateral breast is crucial. There can be very subtle changes such as progressive shrinkage or enlargement or reduced compressibility of the involved breast 9. Imaging often underestimates the disease.

The sensitivity of mammography for the detection of ILC reportedly ranges between 57-81% 8. Because of the limitations of mammography in detecting ILC, other modalities, such as sonography and MR imaging, are being used in evaluating clinically suspicious findings and known cancers to assess the extent of disease. ILC are more commonly seen on the craniocaudal (CC), compared to the mediolateral oblique (MLO).

Mammographic findings in order of frequency are:

  • spiculated mass lesion (most common)
  • asymmetrical densities (3-25% 6)
  • opacities or architectural distortions (10-25% 6)
  • microcalcifications (<10% 1)
  • 16% of ILC are mammographically occult or benign

The most common sonographic appearance is that of a heterogeneous, hypoechoic mass with angular or ill-defined margins and posterior acoustic shadowing. An ill-defined heterogenous infiltrating area of low echogenicity with disproportionate posterior shadowing is one of the ILC sonographic characteristics.

Due to its propensity for multicentricity, breast MRI is usually recommended in many countries when histology of a lesion reveals ILC.

Despite the difficulties of mammographic diagnosis and the propensity for multiplicity and bilaterality, the overall survival rate for patients with ILC of a given size and stage is believed to be slightly higher than for patients with invasive ductal carcinomas 8. Due to the diffuse invasive nature of this tumor, positive resection margins can be common.

It is thought to have been first described by Cornil in 1865 10.

Breast imaging and pathology
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Article information

rID: 13169
System: Breast, Oncology
Synonyms or Alternate Spellings:
  • Invasive lobular carcinoma
  • Invasive lobular carcinoma (ILC)
  • Invasive lobular cancer of the breast
  • Invasive lobular cancer
  • Infiltrating lobular carcinoma
  • Infiltrative lobular carcinoma of the breast
  • Infiltrative lobular carcinoma of breast
  • Infiltrating lobular carcinoma of the breast
  • Infiltrating lobular carcinoma of breast

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Cases and figures

  • Case 1: on MRI
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  • Case 2
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  • Case 3: incidental finding
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  • Case 4
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