Lobular Breast Cancer Updates

New Research, Treatment Advances, and Clinical Insights

Before we dive into the latest research and updates in lobular breast cancer, here's a little peek at what I've been up to recently outside of the clinic!

I recently recorded a podcast with Perry as part of their new Seen & Heard conversations. Miranda McKeon and I spoke about breast cancer, diagnosis, treatment, survivorship, menopause and perimenopause, sexual health and so much more! I can’t wait to share this conversation with you when it is out.

Much of what we discussed is covered in my upcoming book, Beyond The Pink: Navigating Life, Health, and Breast Cancer! The book comes out on 9/29/2026 and for anyone who has pre-ordered, I am hosting a live virtual Beyond The Pink Book Club on 7/22/2026 at 7pm EST.

Submit your pre-order receipt here (open to US and Canada) and you’ll get the Zoom link shortly before the event to join. It will also be recorded if you can’t make it live. Some of the topics we will be talking about include: systemic hormones in breast cancer (including testosterone), vaginal estrogen, updates in treatment, cardiovascular health and MORE (and I’ll be answering your questions!) Can’t wait to see you there!

Let’s now dive into lobular breast cancer updates:

Lobular breast cancer is the second most common type of breast cancer, accounting for approximately 10-15% of cases, and the incidence of lobular breast cancer is increasing.¹ Despite this, much of what we know about breast cancer comes from studies in invasive ductal carcinoma (IDC). As a result, lobular breast cancer is often treated as though it behaves the same way as ductal carcinoma, but that is not the case.

Here are some key facts about lobular breast cancer:

• ILC originates in the lobules and/or the terminal duct lobular units (lobule and small duct) of the breast and the cancer cells commonly grow in a single-file or sheetlike pattern, instead of forming a discrete lump. This is why it can be harder to detect lobular breast cancers on a mammogram compared to ductal breast cancers.

• ILC is characterized by loss of E-cadherin, a protein that normally helps cells adhere to one another. Loss of this protein contributes to the characteristic single-file growth pattern seen in lobular cancers.

• Are more likely to be bilateral (in both breasts).

• Breast MRI is recommended for lobular breast cancers because it can better define the extent of disease than mammography alone.

• Invasive lobular cancer is generally less sensitive to chemotherapy than invasive ductal cancers. (This can differ for pleomorphic lobular cancers which are a variant of invasive lobular cancers and tend to be faster growing and higher grade).

• Most lobular cancers are hormone receptor-positive. HER2-positive and triple-negative lobular cancers are uncommon, although they do occur.

• ILC has distinct patterns of metastatic spread. In addition to common metastatic sites such as bone, lung, and liver, lobular cancers are more likely than ductal cancers to spread to the gastrointestinal tract, peritoneum, and ovaries.

Although treatment recommendations for lobular and ductal breast cancers are often grouped together, these biologic and clinical differences matter. The type of cancer should be considered when making diagnostic and treatment decisions.

A new study published in the journal, ESMO Open, by Nader-Marta et al. looks at characteristics, treatment patterns, and overall survival of nearly 52,000 patients with stage I-III breast cancer diagnosed in Belgium between 2008-2014, comparing lobular breast cancer with other breast cancer types.² Of 51,815 eligible patients, 7593 (14.6%) had invasive lobular cancers. 91% of the patients with ILC had estrogen receptor positive/HER2-negative cancer. 6.1% had ER+/HER2+ disease, 0.8% had ER-/HER2+ disease and 1.9% had triple negative breast cancer.

What did they find? Compared with patients with other breast cancer subtypes, patients with ILC:

• Were older at diagnosis (median age 62 vs. 59 years)

• Were more likely to present with larger primary tumors (T3–T4 disease; 16.5% vs. 7.4%)

• Were more likely to have more extensive lymph node involvement (N3 disease; 5.4% vs. 2.9%)

• Were less likely to have high-grade (grade 3) tumors (19.3% vs. 40.7%)

This illustrates one of the paradoxes of lobular breast cancer. Although it is typically lower grade and hormone receptor-positive, it is often diagnosed at a more advanced stage, likely because its infiltrative growth pattern makes it more difficult to detect on physical examination and mammography.

What about outcomes?

• Patients with ILC experienced lower early mortality but higher late mortality, consistent with prior studies demonstrating that lobular breast cancer can remain at risk for recurrence and breast cancer-related events many years after diagnosis. Overall survival was similar between patients with invasive lobular carcinoma (ILC) and invasive ductal carcinoma during the first several years after diagnosis. Around 8 to 9 years, the survival curves began to separate, with outcomes becoming less favorable for patients with ILC.

• Survival varied by lymph node stage. Patients with no cancer in the lymph nodes (N0) had slightly better overall survival, while those with extensive lymph node involvement (N3) had worse overall survival than patients with other breast cancer subtypes.

• There were worse outcomes among patients with ILC treated with neoadjuvant therapy (treatment given before surgery). ILC was less likely than ductal breast cancer to respond to neoadjuvant therapy, with about 66% lower odds of complete or partial response. The finding was most consistent in ER-positive/HER2-negative disease. No clear difference was seen in HER2-positive cancers (compared to ductal breast cancer), and the triple-negative result was not consistent across all analyses. (This may be in part due to the fact is that ILC is more often clinically and radiologically underestimated at baseline compared with ductal carcinoma, which may result in underappreciation of the true disease extent and complicate the evaluation of response to neoadjuvant therapy).

Importantly, this does not mean chemotherapy does not work in lobular breast cancer. Rather, it reflects that lobular cancers have distinct biology and often respond differently to systemic therapy than ductal cancers.

A study was just published in early July 2026 in the Annals of Surgical Oncology by Fasano G et al.: “Clinical Impact and Outcomes of Neoadjuvant Systemic Therapy for Invasive Lobular Carcinoma”³ This study looked at 853 patients with non-metastatic classic ILC (not pleomorphic) that received neoadjuvant systemic therapy followed by surgery. 715 patients received neoadjuvant chemotherapy and and 138 patients received neoadjuvant endocrine therapy. Most of the patients receiving neoadjuvant therapy had large primary tumors with lymph node positive disease. Overall, 87.6% of patients had HR-positive tumors, with 9.3% having HER2+ disease and 4.1% with triple negative tumors. 9.3% of patients had a pathologic complete response in the lymph nodes (meaning no cancer in the lymph nodes at time of surgery after neoadjuvant therapy). Patients with a nodal pCR had better survival outcomes compared to those without. They found that:

• Lymph node response may be more important than breast response. Patients who achieved a pathologic complete response (pCR) in the lymph nodes had better long-term outcomes.

• Neoadjuvant endocrine therapy performed similarly to chemotherapy in this predominantly hormone receptor-positive ILC population after adjusting for differences between the groups.

• Sentinel lymph node biopsy after neoadjuvant therapy appeared safe in appropriately selected patients, supporting continued efforts to reduce the extent of axillary surgery when possible.

Take Home Points

• Lobular breast cancers behave differently and we need to incorporate this into our treatment planning. Lobular cancers differ in how they grow, how they are detected, how they spread and respond to treatment.

• Both stage at diagnosis and the unique biology of lobular breast cancer likely contribute to long-term outcome differences. Because ILC often grows in a diffuse, single-file pattern that is more difficult to detect on mammography, it is frequently diagnosed at a more advanced stage, while its distinct biology may also contribute to differences in long-term outcomes.

• Some of the differences in outcomes may reflect challenges in detecting distant metastases in ILC with standard imaging. There has been recent interest in using novel imaging technologies such as FES-PET, which is a newer PET tracer designed to detect estrogen receptors.

• For more information on lobular BC, Lobular Breast Cancer Alliance is a fantastic resource.

• Recently, I had Dr. Shannon Klingman on my podcast - Dr. Klingman is a OB-GYN and lobular breast cancer survivor and recently made a historic $1 million donation to the Lobular Breast Cancer Alliance for lobular breast cancer research, a donation that I know will be transformational. Take a listen to our conversation - you will learn a lot! You can also watch it on YouTube.

• Clinicaltrials.gov is an excellent resource to search for lobular BC specific trials.

• Linking here to my Substack on lobular breast cancer updates in June 2025:

As we continue to better understand the unique biology of ILC, there is increasing recognition that patients with lobular breast cancer deserve studies specifically designed for this disease rather than relying on evidence generated primarily from ductal breast cancer.

I am hopeful that a better understanding of lobular breast cancer will ultimately lead to more personalized imaging strategies, more individualized treatment decisions, and, hopefully, improved outcomes. Share your experiences with lobular breast cancer whether as a patient or a clinician! Let’s have a conversation about it.

1. Giaquinto AN, Freedman RA, Newman LA, Jemal A, Siegel RL. Lobular breast cancer statistics, 2025. Cancer. 2025 Oct 15;131(20):e70061. doi: 10.1002/cncr.70061. PMID: 41055508.

2. Nader-Marta G, Ameye L, Martins-Branco D, Salgado R, Van Damme N, Verbeeck J, Aftimos P, Buisseret L, Paesmans M, Molinelli C, Mayer EL, Lambertini M, Van Baelen K, Desmedt C, Piccart M, de Azambuja E. Long-term outcomes and treatment response in early-stage invasive lobular carcinoma: insights from a nationwide population-based study. ESMO Open. 2026 Jun 12;11(7):107731. doi: 10.1016/j.esmoop.2026.107731. Epub ahead of print. PMID: 42284621.

3. Fasano GA, Mouabbi J, Johnson HM, Lin HY, Wanis KN, Sun SX, Lucci A, Valero V, Mitchell M, Shen Y, Hunt KK, Kuerer H. Clinical Impact and Outcomes of Neoadjuvant Systemic Therapy for Invasive Lobular Carcinoma. Ann Surg Oncol. 2026 Jul 3. doi: 10.1245/s10434-026-20130-4. Epub ahead of print. PMID: 42399515.