Breast Neuroendocrine Cancer

Key characteristics of breast neuroendocrine cancer

Breast neuroendocrine cancer has several defining features that influence how it is diagnosed and treated.

Hormone receptor status

Some tumours may have the following hormone receptor characteristics:

• Oestrogen receptor (ER) positive
• Progesterone receptor (PR) positive
• HER2 negative

This means some patients are eligible for hormone (endocrine) therapy.

Neuroendocrine markers

Diagnosis depends on identifying specific markers in tumour cells, including:

• Chromogranin A
• Synaptophysin

These markers confirm neuroendocrine differentiation and distinguish this cancer from standard breast cancers.

Age and demographics

• Most commonly diagnosed in women in their 60s or 70s
• Can occur in younger women and, rarely, in men

Primary vs secondary disease

It is important to confirm whether the tumour:

• Originated in the breast (primary), or
• Spread to the breast from another organ (secondary metastasis)

This distinction significantly impacts treatment decisions.

Types and classification

Breast neuroendocrine cancers are classified based on how the tumour cells look and behave.

Well-differentiated neuroendocrine tumours

• Closely resemble normal cells
• Usually slow-growing
• Often have a better prognosis

Poorly differentiated neuroendocrine carcinomas

• Include small cell and large cell types
• Grow rapidly and behave aggressively
• Require more intensive treatment

Invasive breast cancers with neuroendocrine features

Some standard breast cancers show partial neuroendocrine differentiation. These are treated more like typical breast cancers but still require careful evaluation.

Symptoms of breast neuroendocrine cancer

Symptoms are usually the same as other types of breast cancer.

Common signs include:

• A new lump or thickening in the breast or underarm
• Changes in breast size or shape
• Skin dimpling or puckering
• Nipple changes such as inversion or discharge

Less commonly, if the tumour produces hormones, symptoms may include:

• Flushing
• Diarrhoea

However, hormone-related symptoms are rare in breast neuroendocrine cancer compared to other neuroendocrine tumours.

How breast neuroendocrine cancer is diagnosed

Diagnosis involves a combination of imaging, biopsy, and specialised testing.

Imaging tests

Initial investigations may include:

• Mammogram
• Ultrasound
• MRI

These help identify suspicious areas but cannot confirm the subtype.

Biopsy and histopathology

A tissue biopsy is essential. Under the microscope, specialists assess:

• Cell structure (differentiation)
• Growth rate (grade)

Immunohistochemistry

This is the key step for confirming neuroendocrine cancer. Tumour cells are tested for:

• Chromogranin A
• Synaptophysin

If a significant proportion of cells express these markers, a neuroendocrine diagnosis is made.

Additional imaging for NET features

In some cases, further scans may be used:

• PET scans
• Somatostatin receptor imaging (e.g. DOTATATE PET)

These help determine if NET-specific treatments may be appropriate.

Treatment options for breast neuroendocrine cancer

Treatment is tailored to the individual and depends on:

• Tumour size and location
• Grade and stage
• Hormone receptor status
• Whether the cancer has spread

Surgery

Surgery is the primary treatment for early-stage disease and may include:

• Breast-conserving surgery (lumpectomy)
• Mastectomy

Lymph nodes may also be assessed or removed.

Hormone therapy

Because most tumours are hormone receptor-positive, endocrine therapy is commonly used:

• Tamoxifen
• Aromatase inhibitors

These help reduce the risk of recurrence.

Chemotherapy

Chemotherapy may be recommended for:

• High-grade tumours
• Aggressive subtypes such as small cell carcinoma
• Advanced or metastatic disease

Some regimens may include platinum-based drugs, particularly for poorly differentiated cancers.

Radiotherapy

Radiotherapy is often used after surgery to reduce recurrence risk, following standard breast cancer protocols.

Targeted and NET-specific therapies

In selected cases, particularly where tumours show neuroendocrine characteristics, additional treatments may be considered:

• Peptide receptor radionuclide therapy (PRRT) for tumours with somatostatin receptors
• Targeted therapies
• Clinical trials exploring new treatment approaches

Prognosis and long-term outlook

Prognosis varies depending on tumour type and stage. Factors that influence outcomes include:

• Tumour grade (low vs high)
• Stage at diagnosis
• Hormone receptor status
• Response to treatment

Many breast neuroendocrine cancers are slow-growing and have a favourable prognosis when detected early. However, high-grade tumours can behave more aggressively and require intensive treatment.

Long-term follow-up is important, as recurrence can occur years after initial treatment.

Advanced considerations and emerging research

Because breast neuroendocrine cancer is rare, research is ongoing to better understand and treat it.

Molecular and targeted therapies

Researchers are exploring precision medicine approaches based on tumour genetics

Theranostics

This approach intergrates diagnosis and treatment using the same molecular target, particularly in tumours with neuroendocrine features.

Clinical trials

Patients may benefit from clinical trials due to:

• Limited standardised treatment pathways
• Access to emerging therapies

Support and specialist care

Managing a rare cancer can be complex, and specialist support is essential.

NeuroEndocrine Cancer Australia provides:

• Access to NET specialist doctors
• NET nurse support via telehealth
• Dietitian and counselling services
• Education and patient resources
• Guidance on clinical trials

Because this cancer overlaps both breast oncology and neuroendocrine care, patients may benefit from multidisciplinary teams that include:

• Oncologists
• Surgeons
• Endocrinologists
• Nuclear medicine specialists

If you’ve been diagnosed with a breast NET, or know someone who has been diagnosed, here are some next steps to take.

• Confirm tumour stage and pathology findings
• Understand whether further treatment is needed
• Discuss follow-up with a specialist

For guidance and support, contact the NECA NET Nurse.