Inflammatory breast cancer (IBC) is a rare and aggressive form of breast cancer, accounting for a small percentage of all diagnoses. It is distinct from more common types due to its unique clinical presentation and rapid progression. Understanding if IBC is hereditary requires distinguishing between cancers that arise spontaneously and those caused by an inherited mutation. Inherited genetic mutations significantly increase the risk for some cancers, making this a central concern for patients and families.
Defining Inflammatory Breast Cancer
Inflammatory breast cancer is characterized by rapid onset, often mimicking a severe breast infection rather than a typical tumor. It is rare, making up only 1% to 5% of all breast cancer cases. This aggressive disease is defined by cancer cells blocking the lymph vessels in the skin, causing the breast to look “inflamed.”
The clinical presentation of IBC usually does not involve a distinct lump felt or seen on a mammogram. Signs develop quickly, often over weeks or months, including a rapid increase in breast size, warmth, and a reddened, pink, or bruised appearance over at least one-third of the breast. The skin may also develop a pitted or thickened texture, known as peau d’orange. Because these symptoms are often mistaken for mastitis, a common infection, diagnosis requiring a biopsy can be delayed.
The Link Between IBC and Inherited Genetics
Most cancers, including the majority of breast cancer cases, are sporadic, resulting from random mutations acquired during a person’s lifetime. Hereditary cancer arises from a pathogenic gene variant passed down from a parent, significantly increasing the lifetime risk of developing the disease.
Inflammatory breast cancer is overwhelmingly considered a sporadic malignancy, rarely caused by a single inherited mutation. While up to 10% of IBC cases may have a hereditary component, most are not tied to a known inherited genetic syndrome. This contrasts with non-inflammatory breast cancer, where 5% to 10% of cases are attributed to inherited genetic mutations.
A family history of breast cancer increases the overall risk for IBC, but this does not mean the IBC itself is directly inherited. This familial risk suggests shared genetic susceptibility or environmental factors contribute to the risk without a single, highly penetrant gene being the direct cause. A first-degree family history of breast cancer is a risk factor for IBC, similar to other forms of breast cancer.
Identifying Key Genetic Mutations
When a hereditary link is suspected, testing focuses on established breast cancer susceptibility genes, such as BRCA1 and BRCA2. These genes are tumor suppressors that normally help repair damaged DNA. An inherited mutation in either gene substantially raises the risk for breast and ovarian cancer.
The association between BRCA mutations and IBC is less common than with other breast cancer subtypes. Women carrying a BRCA1 or BRCA2 mutation have a higher risk of developing IBC compared to those without the mutation. The rate of BRCA variants in IBC patients is similar to or slightly lower than in non-IBC cases. Research suggests IBC patients who test positive for a BRCA mutation are often diagnosed at a significantly younger age.
Genetic testing is not routinely recommended for all IBC patients but is advised when personal or family history meets established criteria for hereditary cancer risk. These criteria include diagnosis at a young age, a strong family history of breast or ovarian cancers, or the presence of triple-negative breast cancer. Genetic counseling evaluates a person’s risk and determines whether testing for genes like BRCA1, BRCA2, TP53, or PTEN is appropriate.
Non-Genetic Risk Factors for IBC
Since IBC is primarily a sporadic disease, non-inherited factors significantly contribute to a person’s risk. These factors often relate to demographic and health characteristics, though the precise cause for most cases remains unknown.
Demographic factors play a role, as IBC tends to be diagnosed in women at a slightly younger average age compared to other breast cancer types. Studies indicate that African American women may be diagnosed with IBC more frequently than women of other races.
Body weight is a notable non-genetic factor, as being overweight or obese increases the risk for IBC regardless of menopausal status. A high body mass index (BMI) has been identified as an independent risk factor for this cancer type.