Lobular carcinoma in situ (LCIS) is a non-invasive neoplastic proliferation arising from epithelial cells of terminal ductules and acini of breast lobules that has not breached the basement membrane. LCIS is typically discovered incidentally — it shows no specific findings on mammography and is most often diagnosed incidentally on biopsy performed for another reason. LCIS is less a precancerous lesion itself than a risk marker that increases the risk of bilateral breast cancer — it raises the risk of developing invasive carcinoma in either breast equally by 7-12 fold. It tends to be multifocal in 30-40% and bilateral in 20-30% of cases. There is a strong association with invasive lobular carcinoma (ILC) but risk of invasive ductal carcinoma is also increased. It typically occurs in premenopausal women (age 40-50). The pleomorphic LCIS variant shows more aggressive biological behavior and may present with calcifications similar to DCIS.
Age Range
40-60
Peak Age
50
Gender
Female predominant
Prevalence
Uncommon
LCIS is a proliferation of E-cadherin negative neoplastic cells lining the acini and small ductules of the terminal ductal lobular unit. E-cadherin loss is the most defining molecular feature of LCIS — loss of this cell-cell adhesion molecule causes cells to grow in a discohesive pattern. This discohesive growth shows that LCIS shares a common pathological mechanism with invasive lobular carcinoma (ILC) — ILC is also E-cadherin negative and shows 'Indian file' (single file) infiltration pattern. The primary reason LCIS is invisible on mammography is that neoplastic cells do not distort the lobular architecture, do not produce desmoplastic reaction (stromal fibrosis), and typically do not generate necrosis or calcification. Although lobules are filled, the overall breast parenchyma is structurally preserved — therefore mass, distortion, or calcification is not expected on mammography. In the pleomorphic LCIS variant, cells are larger and more atypical, central necrosis may occur, and dystrophic calcification similar to DCIS can form — therefore pleomorphic LCIS may present with calcifications on mammography.
The most defining 'finding' of LCIS is actually the absence of findings — being invisible on mammography, ultrasound, and often MRI is the most characteristic feature of LCIS. This results from E-cadherin negative discohesive cells not producing desmoplastic reaction, necrosis, or calcification.
Classic LCIS is invisible on mammography — does not produce calcifications, mass, or architectural distortion. Breast density is independent of LCIS presence. Diagnosis is made incidentally on biopsy performed for another finding, not through mammographic screening.
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No specific finding detected on mammography; however, as LCIS is typically occult on mammography, a negative mammogram does not exclude LCIS.
LCIS is generally undetectable on contrast-enhanced breast MRI, but in some cases multifocal, regional, or diffuse non-mass enhancement may be seen. Segmental or ductal NME may be more prominent in pleomorphic LCIS. MRI sensitivity for LCIS detection is low (40-60%).
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Bilateral diffuse mild non-mass enhancement is observed on contrast-enhanced breast MRI; this finding is nonspecific in the setting of LCIS and clinical correlation is recommended.
Amorphous or fine pleomorphic calcifications may be seen in the pleomorphic LCIS variant — these calcifications mimic DCIS calcifications. May show grouped or regional distribution. Immunohistochemical E-cadherin negativity confirms LCIS diagnosis.
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Grouped amorphous calcifications are observed; DCIS and pleomorphic LCIS should be considered in the differential diagnosis; stereotactic biopsy with E-cadherin immunohistochemistry is recommended.
LCIS may show mild T2 signal increase in affected lobules but this finding is usually very subtle and may be indistinguishable from background parenchyma. T2 signal changes may be more prominent in pleomorphic LCIS.
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No significant focal signal abnormality is observed on T2-weighted series; LCIS may typically be occult on MRI.
Classic LCIS typically shows no findings on ultrasound. Rarely, nonspecific mild hypoechoic area or focal asymmetric density increase may be seen. US is not the primary modality for LCIS screening but is valuable for detecting accompanying invasive lesions.
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No focal lesion detected on ultrasound; LCIS is typically occult on ultrasound and negative US findings do not exclude LCIS.
Criteria
Small, uniform, round cells — discohesive proliferation filling lobular acini. E-cadherin negative. No necrosis. Low mitotic activity. Most common type (80-90%).
Distinct Features
Occult on all imaging modalities. Evaluated as bilateral risk marker. Active surveillance or chemoprophylaxis (tamoxifen) is recommended. Surgical excision is generally not required (with adequate sampling).
Criteria
Large, atypical cells, nuclear pleomorphism, focal comedo necrosis may be present. E-cadherin negative (differentiating from DCIS). More aggressive biological behavior — management similar to DCIS is recommended.
Distinct Features
May show calcifications on mammography (DCIS-like). Enhancement on MRI may be more prominent. Surgical excision is generally recommended. Recurrence risk is higher than classic LCIS.
Criteria
LCIS characterized by massive distension of lobules. Acini are markedly expanded and filled with neoplastic cells. Central necrosis may be seen. Considered more aggressive than classic LCIS.
Distinct Features
Expanded lobules may sometimes create mass effect — may appear as focal asymmetry or nonspecific lesion on MRI or US. Surgical excision is recommended. Risk of progression to invasive carcinoma is higher than classic LCIS.
Distinguishing Feature
DCIS presents with calcifications (pleomorphic/linear/branching) on mammography — LCIS is typically occult on mammography. DCIS is E-cadherin positive, LCIS is E-cadherin negative. DCIS is a local premalignant lesion, LCIS is a bilateral risk marker.
Distinguishing Feature
ILC is an invasive tumor presenting with mass or non-mass enhancement on MRI — LCIS is typically occult even on MRI. ILC may be occult on mammography but detectable on US/MRI. Both are E-cadherin negative but ILC has breached the basement membrane.
Distinguishing Feature
Fibroadenoma appears as a well-circumscribed, oval, hypoechoic solid mass on US — LCIS is typically invisible on US. Fibroadenoma shows oval mass or coarse calcification on mammography. Fibroadenoma is a benign neoplasm without malignancy risk.
Distinguishing Feature
IDC forms spiculated or irregularly marginated mass on mammography — LCIS does not form a mass. IDC appears as hypoechoic, irregularly marginated mass with posterior acoustic shadowing on US. IDC is E-cadherin positive while LCIS is negative.
Urgency
routineManagement
surveillanceBiopsy
Not NeededFollow-up
annualClassic LCIS is managed as a risk marker — surgical excision is generally not required (with adequate sampling on core biopsy). Management options: (1) Active surveillance — annual mammography + 6-monthly clinical examination, annual MRI screening in high-risk patients. (2) Chemoprophylaxis — tamoxifen or raloxifene for 5 years (~50% risk reduction). (3) Bilateral prophylactic mastectomy — in very high-risk selected cases (BRCA + LCIS). In pleomorphic and florid LCIS, management similar to DCIS is recommended — surgical excision + clear margins. Lifetime risk of invasive carcinoma after LCIS diagnosis is 20-30%.
LCIS is a risk marker, also considered a precursor lesion. Annual mammography and MRI high-risk screening is recommended. Chemoprophylaxis (tamoxifen/raloxifene) may be considered for risk reduction. Bilateral prophylactic mastectomy may be discussed in rare cases.