invasive lobular carcinoma of the breast

Invasive lobular carcinoma is the most common special type of invasive breast cancer after invasive breast carcinoma of no special type (invasive ductal carcinoma not otherwise specified).

Epidemiology

They represent 5-10% of all breast cancer.

Associations

There is a greater rate of contralateral breast cancer in invasive lobular carcinoma compared with invasive carcinoma of no special type, with a 5-year rate of bilateral cancer of 8% (4% synchronous and 4% metachronous tumors).

Pathology

Microscopic appearance

Invasive lobular carcinoma is characterized microscopically by malignant monomorphic cells that form loosely dispersed linear columns that invade the normal tissues and encircle ducts. Compare this behavior with that of invasive carcinoma of no special type (ductal not otherwise specified), which more commonly presents as a mass with vigorous desmoplastic response. Cells of invasive lobular carcinoma often preserve the architecture of the ducts, which limits the sensitivity of detection using mammography.

Most invasive lobular carcinomas are grade 2 in the Nottingham histological grading system .

Markers

Loss of E-cadherin is a specific biomarker for invasive lobular carcinoma as opposed to invasive breast carcinoma of no special type, although 15% of invasive lobular carcinoma are positive for E-cadherin .

The majority of invasive lobular carcinomas have the following receptor profile :

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

Radiographic features

Invasive lobular carcinoma 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 . Imaging often underestimates the disease.

Mammography

The sensitivity of mammography for the detection of Invasive lobular carcinoma reportedly ranges between 57-81% . 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. Invasive lobular carcinomas 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%)
  • opacities or architectural distortions (10-25% )
  • microcalcifications (<10%)
  • 16% of invasive lobular carcinoma are mammographically occult or benign
Breast ultrasound

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 sonographic characteristics of invasive lobular carcinoma.

Breast MRI

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

Treatment and prognosis

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

History and etymology

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