Lobular breast cancer, also known as invasive lobular carcinoma (ILC), is a type of breast cancer that originates in the milk-producing lobules of the breast. Distinguished from the more common invasive ductal carcinoma (IDC), which begins in the milk ducts, ILC typically presents with a unique pattern of spread and growth. ILC is the second most common form of breast cancer and accounts for about 10% to 15% of all breast cancers.
Most commonly diagnosed in older women, although it can occur at any age, ILC is often challenging to detect due to its diffuse nature. The treatment and prognosis for lobular breast cancer generally align with other types of breast cancer, involving a combination of surgery, radiation, chemotherapy, and hormone therapy, depending on the individual case.
Continue reading to learn how lobular breast cancer is different from other forms of breast cancer, its connections with genetic mutations, and how ILC is diagnosed and treated.
How is lobular breast cancer different from other subtypes of breast cancer?
Invasive lobular carcinoma (ILC) is a type of breast cancer that is recognized as biologically distinct from the more common invasive ductal carcinoma (IDC).
ILC is distinct from other forms of breast cancer in several ways:
Cellular characteristics: ILC is characterized by the loss of the cell adhesion molecule E-cadherin, leading to discohesive cells that proliferate into single-file strands. This unique growth pattern contributes to the difficulty in detecting ILC using standard imaging techniques.
Hormone receptor status: ILC tumors are often estrogen receptor- (ER) positive, affecting treatment choices and responsiveness.
Metastatic patterns: Unlike ductal carcinomas that form distinct lumps, ILC grows in sheets throughout the breast tissue, making tumors more challenging to detect. It’s also more likely to be multifocal (occurring in multiple sites) and bilateral (occurring in both breasts).
What genetic and molecular factors are associated with lobular breast cancer?
ILC often exhibits specific genetic mutations and molecular features distinct from IDC. For example, mutations in the CDH1 gene are commonly associated with ILC, which can affect how cells adhere to each other.
Several genetic and molecular factors have also been linked to ILC, including TP53, PIK3CA, FOXA1, ZNF703, FGFR1, and BCAR4. These factors contribute to the unique molecular characteristics of ILC and may have implications for its development and progression. Here’s an overview of these factors:
TP53 mutations: TP53 is a tumor suppressor gene that plays a crucial role in preventing the growth of cancer cells. Mutations in TP53 have been associated with ILC. TP53 mutations can lead to the loss of its tumor-suppressing function, allowing cancer cells to proliferate more rapidly and evade cell cycle checkpoints.
PIK3CA mutations: PIK3CA is a gene involved in the PI3K/AKT/mTOR signaling pathway, which regulates cell growth and survival. Mutations in PIK3CA are common in various cancer types, including ILC. These mutations can activate the pathway, promoting cell growth and survival.
FOXA1 expression: FOXA1 is a transcription factor that plays a role in hormone receptor signaling. ILC often exhibits high levels of FOXA1 expression. This can influence the behavior of hormone receptor-positive ILC and its response to hormone therapy.
ZNF703 amplification: Amplification of the ZNF703 gene has been observed in some cases of ILC. ZNF703 is involved in gene regulation and may contribute to the growth and progression of ILC.
FGFR1 amplification: Amplification of the FGFR1 gene has also been associated with ILC. FGFR1 is a receptor tyrosine kinase that can promote cell proliferation when amplified.
BCAR4 expression: BCAR4 is a long non-coding RNA (lncRNA) that has been linked to the progression of ILC. It may play a role in the invasive behavior of ILC cells.
These genetic and molecular factors can interact and influence the biology of ILC, making it distinct from other breast cancer types, such as invasive ductal carcinoma (IDC). Understanding these molecular characteristics is important for tailoring treatment strategies for individuals diagnosed with ILC.
In practice, the presence of specific mutations or molecular alterations in ILC tumors may guide treatment decisions. For example, hormone receptor-positive ILC may respond well to hormone therapy, while targeted therapies that inhibit pathways like PI3K/AKT/mTOR may be considered for cases with PIK3CA mutations. Additionally, ongoing research continues to explore these molecular factors and their potential as therapeutic targets for ILC.
How is lobular breast cancer detected?
Detecting ILC poses significant challenges given its unique characteristics and how it presents:
Mammography limitations: Since ILC does not usually form distinct masses, it may not appear on mammograms, or it may appear as asymmetrical tissue thickening rather than a distinctive mass. For this reason, ILC can be more challenging to diagnose early. Know what to look and feel for: changes in breast shape or texture or mild, diffuse pain. Pay attention to subtle changes and always report them promptly to your doctor.
Breast ultrasound: Ultrasound imaging may be used in conjunction with mammography to evaluate areas of concern in the breast. It can help distinguish between solid masses and cysts and provide additional information about the characteristics of a lesion.
MRI as a superior modality: Magnetic resonance imaging (MRI) is an exceptionally sensitive technique for detecting ILC, showcasing an impressive sensitivity range of 94% to 99%. The high level of accuracy is due to MRI’s advanced imaging capabilities, which are adept at discerning the distinct and often subtle tumor characteristics unique to ILC.
Unlike other imaging modalities, MRI excels in providing detailed images of the breast tissue, enabling it to detect ILC’s atypical growth patterns and diffuse spread, which traditional methods like mammography might miss. MRI’s superior imaging proficiency in identifying the intricate and distinct features of ILC enhances the accuracy of diagnoses, ensuring earlier and more effective treatment interventions.
What treatment is available for lobular breast cancer?
When caught early, ILC generally has a similar prognosis to invasive ductal carcinoma. Surgery is often the first line of treatment, followed by radiation, chemotherapy, hormone therapy, or targeted drugs as needed.
Surgery: Often the first line of treatment, which may include lumpectomy or mastectomy, coupled with an evaluation of lymph node involvement.
Lumpectomy: This involves the removal of the cancerous tumor along with a margin of surrounding healthy tissue. It is an option for early-stage lobular breast cancer.
Mastectomy: In some cases, a mastectomy, which is the removal of the entire breast, may be recommended. This decision depends on factors such as the size of the tumor, its location, and individual preference.
Sentinel lymph node biopsy or axillary lymph node dissection: During surgery, a sentinel lymph node biopsy or axillary lymph node dissection may be performed to determine if the cancer has spread to nearby lymph nodes.
Radiation therapy: Typically used post-surgery to target any residual cancer cells in the breast and surrounding areas.
Chemotherapy: Used to kill cancer cells throughout the body, either before surgery to shrink the tumor or after surgery to eliminate remaining cancer cells.
Targeted therapy: Involves treatments that specifically target the characteristics of cancer cells, with a reduced likelihood of harming healthy cells.
Antihormone therapy: Especially effective in ILC due to its high ER positivity, this therapy reduces estrogen levels in the body, thereby inhibiting the growth of breast cancer cells.
Endocrine therapy: Favored due to ILC’s low chemosensitivity and reduced pathological response rates to chemotherapy.
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Note: This article is designed to provide general information and not replace professional medical advice. Always discuss your options with your healthcare provider.
Lobular breast cancer stories from the SBC community:
On the Podcast: Breast Cancer Conversations
Inflammatory and Lobular Breast Cancer: Patient Advocates Share SABCS Insights
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