What is atypical lobular hyperplasia?

Atypical Lobular Hyperplasia (ALH)

Atypical lobular hyperplasia (ALH) is a proliferative breast lesion with atypia that significantly increases the risk of developing breast cancer, with a lifetime risk of approximately 4-5 times that of the general population, equating to a continuous risk of about 0.5% to 1.0% per year. 1

Definition and Classification

ALH is part of a spectrum of lobular neoplasia that includes:

• Atypical lobular hyperplasia (ALH): Less extensive proliferation
• Lobular carcinoma in situ (LCIS): More extensive proliferation

Both conditions are characterized by proliferation of cells within the terminal duct lobular units of the breast. ALH is classified as a "proliferative lesion with atypia" along with atypical ductal hyperplasia (ADH), LCIS, and flat epithelial atypia. 1

Pathological Features

ALH is characterized by:

• Proliferation of monomorphic cells within the terminal duct lobular units
• Cells that are small with round nuclei
• Incomplete involvement of the lobular units (unlike LCIS which shows more extensive involvement)
• Often an incidental finding on breast biopsy performed for other reasons

Risk Implications

ALH confers significant breast cancer risk:

• 4-5 fold increased risk compared to the general population 1
• Risk is bilateral (affects both breasts equally) regardless of which breast had the ALH 2
• Risk persists long-term, with many subsequent cancers occurring more than 15 years after the ALH diagnosis 1
• Risk is doubled if there is an associated family history of breast cancer 1

Clinical Management

When ALH is found on core needle biopsy:

• Historically, surgical excision was recommended for all ALH cases
• Recent evidence suggests that in specific circumstances, imaging surveillance may be appropriate for minimal ALH (≤3 foci) with radiologic-pathologic concordance 3, 4
• Surgical excision is still recommended when:
  • There is radiologic-pathologic discordance
  • ALH is extensive (>3 foci)
  • ALH is associated with pleomorphic features
  • ALH involves more than 4 terminal ductal units 2

For surveillance after diagnosis:

• Regular clinical examinations every 6-12 months
• Annual diagnostic mammography 2
• Consider supplemental screening based on breast density and overall risk 1
• Consistent long-term surveillance is necessary due to the persistent elevated risk 2

Risk Reduction Options

For women with ALH, risk reduction strategies should be discussed:

• Chemoprevention with selective estrogen receptor modulators:

  • Tamoxifen for premenopausal women (reduces risk by approximately 46%) 2
  • Tamoxifen or raloxifene for postmenopausal women 2

• Surgical options:

  • Bilateral risk-reduction mastectomy is generally not recommended for ALH alone
  • May be considered in special circumstances (BRCA1/2 mutations, strong family history) 2

Prognosis and Outcomes

The natural history of ALH shows:

• Both ALH and ADH behave similarly in terms of later breast cancer outcomes 5
• There is a 2:1 ratio of ipsilateral to contralateral breast cancer development 5
• Ipsilateral predominance is marked in the first 5 years after diagnosis 5
• Subsequent invasive cancers are predominantly ductal (not lobular), with approximately two-thirds being moderate or high grade 5

Common Pitfalls in Management

• Overtreatment of minimal ALH with unnecessary surgical excision
• Inadequate long-term follow-up (risk persists for decades)
• Failure to discuss risk reduction options with patients
• Not recognizing that ALH increases risk for both breasts equally
• Confusing ALH with other atypical lesions that may require different management

ALH represents an important risk marker that requires appropriate management and surveillance to reduce the risk of subsequent breast cancer development.