Invasive lobular carcinoma (ILC) of the breast is the second most common type of primary breast cancer, accounting for 10-15% of cases. 6-28% of cases are bilateral, approximately twice the risk of invasive ductal carcinoma.
Risk factors for breast cancer include:
â€¢ Age > 50
â€¢ Genetics (BRCA1, BRCA2, HER2, p53)
â€¢ Personal history of breast cancer
â€¢ Family history, especially in first-degree relative
â€¢ Previous breast biopsy showing benign conditions (e.g. LCIS or atypical hyperplasia)
â€¢ Menarche before age 12 or menopause after age 55
â€¢ Delayed childbirth after age 30
â€¢ High-fat diet
â€¢ Obesity (weight gained as adult)
â€¢ Previous radiation therapy, e.g. tx Hodgkinsâ€™ disease
â€¢ Combined estrogen and progesterone replacement therapy (CHRT)
It has been historically difficult to diagnose early due to lack of pathomnemonic radiographic signs. Classically, ILC exhibits the â€˜Indian fileâ€™ appearance of small, regular non-cohesive cells arranged in single files. The subtle mammographic findings are often due to malignant cells permeating the parenchyma around normal ducts, inducing little connective tissue reaction.
Physical exam may also be non-specific in ILC and may include vague areas of thickening which may be confused with benign breast change, especially in the younger patient.
US and MR imaging has been shown to be more sensitive than mammography for invasive cancer, but with the risk of overestimating the extent of the tumor. Combined mammography, clinical exam, and MRI were more sensitive at detecting ILC than any other individual test or combination of tests.
The majority of ILCs are of intermediate histological grade (grade 2) and ER+; prognosis is similar to that of invasive ductal carcinomas of similar grade.
IMAGING FEATURES OF PRIMARY INVASIVE LOBULAR CARCINOMA
â€¢ micro-calcification less frequently observed (6.5-25%) unlike in ductal ca
â€¢ speculated mass
â€¢ asymmetric density without definable margins
â€¢ architectural distortion without an obvious mass
â€¢ better demonstrated on craniocaudal view
Because these subtle findings are often confused with normal glandular tissue, the relative infrequency of micro-calicification, and the insidious growth of the tumor, ILC is often undetected until clinically palpable. At this stage, skin tethering, skin thickening, and nipple retraction are often apparent.
â€¢ useful adjunct to mammography
â€¢ ill-definied hypoechoic mass with acoustic attenuation
â€¢ FNA often do not yield much information due to the relative sparseness of malignancy cells within these tumors
â€¢ wide-bore needle biopsy should be performed if FNAs inconclusive
â€¢ highly sensitive in detecting ILC and the extent of ILC
â€¢ may be of value in preoperative planning as well as the diagnosis of multifocal or contralateral involvement
American College of Radiology (ACR) / Breast Imaging Reporting and Data System (BI-RADS)
BI-RADS Assessment Categories:
Category 0: Need Additional Imaging Evaluation
Category 1: Negative
Category 2: Benign Finding
Category 3: Probably Benign Finding - Short Interval Follow-Up Suggested
Category 4: Suspicious Abnormality - Biopsy Should Be Considered
Category 5: Highly Suggestive of Malignancy - Appropriate Action Should Be Taken
METASTATIC MANIFESTATIONS OF INVASIVE LOBULAR BREAST CARCINOMA
Gastrointestinal, gynecological, peritoneal, retroperitoneal, bone marrow, and leoptomeningeal metastases are more frequently seen with ILC than with IDC. CT, MRI, and PET scans are useful, but somewhat limited in revealing the full extent of metastatic ILC. Knowledge of pattern of metastasis is useful for interpretation of these imaging studies.
â€¢ Bone (most frequent metastasis site)
â€¢ Gastrointestinal â€“
o Esophagus, stomach (produces linitis plastica), small bowel (50% of mets) and large bowel wall thickening
o Can present as obstruction, hemorrhage, or performation
â€¢ Gynecologic â€“
o Uterus â€“ ILC is most common extragenital neoplasm to metastasize to uterus
o Ovary, Vagina, Parametrium
â€¢ Genitourinary system â€“ Direct invation of kidneys and ureters
â€¢ Peritoneum â€“ Manifests as small nodules which may become confluent
â€¢ Retroperitoneum â€“ Ureteric obstruction and hydronephrosis
â€¢ Orbital metastases