By: Amy Zhang, MD and Reza Fardanesh, MD 

Introduction, Demographics, Clinical Presentation

Lobular carcinoma in situ (LCIS) is a noninvasive lesion of the breast considered to be a nonobligate precursor of invasive lobular carcinoma1. The pathologic definition is proliferation of atypical cells filling and distending at least half of the acini in the lobular unit2. In patients diagnosed with primary LCIS, there is a 7.1% incidence of invasive breast cancer at 10 years, with nearly identical incidence in ipsilateral versus contralateral breasts3

LCIS has been described as clinically occult. It is found to be multicentric in most cases and is often bilateral4. Typically, an incidental finding on a biopsy performed for a separate reason, studies report the incidence of LCIS as 0.8-3.8% in open surgical biopsies and 0.02-3.3% of image-guided core needle biopsies. There is a much lower incidence demonstrated in population-based data2.

LCIS is seen most often in premenopausal women (mean age of 49 years)5. In postmenopausal women, long-term HRT use is associated with the risk of developing LCIS6

Imaging Features

The imaging features of LCIS are nonspecific. On mammography, LCIS is most frequently occult5,7. When present, the most common mammographic finding is microcalcifications which may be of variable morphology and distribution, most often grouped and amorphous4. Of note, in many cases microcalcifications are found in tissue adjacent to the focus of LCIS instead of within the LCIS itself5.  

Case: LCIS Figure 1
Figure 1 (circle). Amorphous calcifications with grouped distribution. These underwent stereotactic biopsy, with results of LCIS and atypical lobular hyperplasia (ALH) with calcifications present in ALH.

On sonography, LCIS may appear as oval, hypoechoic masses with circumscribed or microlobulated margins Posterior enhancement is common. In 32% of cases, LCIS is seen as vague shadowing or distortion without a discrete mass8.   

When LCIS is seen on MRI, the most common finding is non-mass enhancement. Most of the non-mass enhancement show persistent enhancement on delayed phase4.

Case: LCIS Figure 2
Figure 2. Focal nonmass enhancement at site of biopsy-proven LCIS.


In LCIS, cells typically show dyscohesion with loss of E-cadherin expression. Pagetoid spread of cells between the epithelial and myoepithelial layers is another common pathologic feature9

Besides classic LCIS, less common variants of LCIS have been recognized. Pleomorphic LCIS demonstrates large, pleomorphic nuclei. Florid LCIS involves marked distension of ducts or terminal duct lobular units. Both pleomorphic and florid LCIS subtypes are often associated with calcifications and comedonecrosis10.


The management of LCIS is currently evolving and varies across institutions, with some recommending surgical excision and others surveillance11,12,13. This is related to the variable upstaging rate of LCIS to invasive breast cancer or to DCIS, which ranges from 2% to 25%11

According to 2023 NCCN guidelines, a core biopsy showing classic LCIS can be managed without surgical excision, which should be considered on a case-by-case basis. If excision is not performed, the patient is recommended to undergo close follow-up with mammogram and breast MRI screening11.

The role of screening MRI in patients with LCIS is not well established. One retrospective study demonstrated additional work-up in 16.7% of patients after excision of LCIS who underwent screening MRI, with PPV of only 20%14

Chemoprevention with selective estrogen receptor modulars or aromatase inhibitors can reduce the risk of breast cancer in patients with LCIS15


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