Breast mucoepidermoid carcinoma is a rare type of breast cancer that includes mucus-producing and squamous-like cells. People with breast mucoepidermoid carcinoma may notice a new breast lump, tenderness, or changes in the skin or nipple, and early symptoms of breast mucoepidermoid carcinoma can be subtle. It typically grows slowly compared with many other breast cancers, but behavior can vary by grade. Treatment often includes surgery, and many also receive radiation or medicine such as hormone therapy or chemotherapy based on tumor features. Survival is generally good for low‑grade tumors, but higher‑grade breast mucoepidermoid carcinoma can carry a higher risk and needs closer follow‑up.
Overview
Breast mucoepidermoid carcinomaSymptoms
Early symptoms of breast mucoepidermoid carcinoma include a new, often painless lump, nipple discharge or inversion, skin dimpling or redness, breast swelling or shape change, and sometimes tenderness or a swollen underarm node.
Outlook and prognosis
Many living with breast mucoepidermoid carcinoma do well, especially when the tumor is low grade and found early. Treatment is often successful and recurrences are uncommon. Higher‑grade tumors carry more risk, so close follow‑up and tailored care matter.
Causes and risk factors
Breast mucoepidermoid carcinoma usually arises from acquired gene changes, often MAML2 fusions, and is rarely inherited. Risk factors resemble general breast cancer: increasing age, chest radiation, hormonal exposure, or family history. Obesity and alcohol may add risk.
Genetic influences
Genetics play a meaningful role in breast mucoepidermoid carcinoma, but data are limited due to its rarity. Tumor changes, like MAML2 gene fusions, are reported and may guide diagnosis and prognosis. Inherited risk appears low; most cases seem sporadic.
Diagnosis
Diagnosis of Breast mucoepidermoid carcinoma starts with breast exam and imaging (mammogram, ultrasound, sometimes MRI). A core needle biopsy confirms the cancer under the microscope. Pathology tests help classify the tumor and guide treatment.
Treatment and drugs
Treatment for breast mucoepidermoid carcinoma often centers on breast-conserving surgery or mastectomy, with lymph node assessment. Many people also receive radiation to lower local relapse risk. Depending on tumor grade and receptors, chemotherapy or targeted endocrine therapy may be recommended.
Symptoms
Many people first notice a new lump or a change in how one breast looks or feels. Symptoms vary from person to person and can change over time. Early symptoms of breast mucoepidermoid carcinoma can be subtle, like a small, painless lump or a bit of nipple discharge. New or persistent breast changes should be checked by a healthcare professional.
A new lump or thickened area in the breast is the most common change people notice. The lump is often painless at first. Any lump that persists should be evaluated.
Breast pain or tenderness can happen, though many cancers are painless. New, one-sided pain that doesn’t follow your cycle deserves attention. Pain alone is more often from noncancer causes.
Spontaneous clear, bloody, or sticky discharge from one nipple is a warning sign. With breast mucoepidermoid carcinoma, discharge may appear without squeezing. Discharge that is new or bloody should be checked promptly.
New inversion, flattening, or scaling of the nipple-areola area can occur. The area may feel tender or look different than the other side. These changes can be subtle.
How people usually first notice Breast mucoepidermoid carcinoma?
Many people first notice breast mucoepidermoid carcinoma as a new lump in the breast that feels firm or irregular, sometimes tender, or as a change in the breast’s shape, skin, or nipple (such as dimpling, redness, or discharge). It’s often found on a routine screening mammogram before it can be felt, especially in people without symptoms. Because this tumor is rare and can resemble more common breast cancers or benign lumps, doctors usually confirm it with imaging followed by a core needle biopsy, which is when the diagnosis becomes clear.
Types of Breast mucoepidermoid carcinoma
Breast mucoepidermoid carcinoma is a rare salivary‑gland–type tumor that arises in breast tissue and tends to behave differently depending on its grade and specific tumor features. Doctors most often classify the types of breast mucoepidermoid carcinoma by histologic grade—low, intermediate, or high—which closely tracks with how fast the cancer grows and the chance it will spread. People may notice different sets of symptoms depending on their situation. When reading about types of breast mucoepidermoid carcinoma, the key differences usually come down to speed of growth, lymph node risk, and likelihood of coming back after treatment.
Low-grade tumors
These cancers grow slowly and often form well-defined lumps that may stay stable for a while. They have a lower chance of spreading to lymph nodes or distant sites.
Intermediate-grade tumors
These sit between low and high grade in speed and behavior. They can grow faster than low-grade tumors and have a moderate risk of lymph node involvement.
High-grade tumors
These are more aggressive, can enlarge over weeks to months, and are more likely to cause pain, skin changes, or nipple symptoms. They carry a higher risk of spreading and coming back after treatment.
Triple-negative variant
Many breast mucoepidermoid carcinomas are negative for estrogen, progesterone, and HER2, which limits benefit from hormone or HER2‑targeted therapies. In these types of breast mucoepidermoid carcinoma, treatment often centers on surgery and may include chemotherapy based on tumor grade and stage.
MAML2‑rearranged tumors
Some tumors show a MAML2 gene fusion, similar to salivary gland counterparts, which is often linked with lower grade and a more favorable outlook. When present, this variant may correlate with slower growth and fewer recurrences.
What genetics can tell you about symptoms
Some breast mucoepidermoid carcinomas carry MAML2 gene fusions, which are linked to slower‑growing tumors and fewer aggressive symptoms like rapid enlargement or skin changes. When MAML2 is absent and other alterations drive growth, doctors may see faster growth, pain, or nipple discharge.
Causes and risk factors
The exact cause of breast mucoepidermoid carcinoma is unclear, and most cases seem to occur by chance. Some risks are modifiable (things you can change), others are non-modifiable (things you can’t). A tumor gene change called a MAML2 fusion is often found and seems to drive growth. General breast cancer risks may still apply, such as older age, prior chest radiation, alcohol use, higher weight, and hormone therapy. Family history of breast cancer and inherited gene variants like BRCA1 or BRCA2 may raise overall breast cancer risk, but links to this rare subtype are not well defined.
Environmental and biological risk factors
Breast mucoepidermoid carcinoma is rare, so most risk insights come from broader breast cancer research. Doctors often group risks into internal (biological) and external (environmental). Below are environmental and biological risk factors for breast mucoepidermoid carcinoma that likely track with other breast cancers, though data for this specific subtype are limited. Having one or more does not mean you will develop this cancer.
Prior high-dose radiation to the chest, especially at a young age, raises breast cancer risk. This is a clear external exposure that can also increase the chance of breast mucoepidermoid carcinoma. Risk tends to be higher with greater dose.
Denser breasts carry higher risk and can make small tumors harder to see on mammograms. Density reflects more gland and fibrous tissue compared with fat. This biological feature is relevant across breast cancer subtypes.
Risk of breast cancers increases as cells age and accumulate wear-and-tear. Hormone patterns also shift over time in ways that can promote tumor growth. This age effect likely applies to breast mucoepidermoid carcinoma.
Longer exposure to natural estrogen can raise breast cancer risk. Estrogen can act like a growth signal for breast cells. This reflects internal hormone patterns over the lifespan.
Genetic risk factors
Understanding which DNA changes drive this rare breast tumor can guide diagnosis and, at times, targeted care. People with the same risk factor can have very different experiences. Most cases of Breast mucoepidermoid carcinoma come from genetic changes that arise only in the tumor itself, not ones you inherit. Here’s what we know about genetic risk factors for Breast mucoepidermoid carcinoma.
CRTC1–MAML2 fusion: A rearrangement joining CRTC1 and MAML2 is the best-documented driver in Breast mucoepidermoid carcinoma. It is found in many cases and helps confirm the diagnosis on molecular testing. Fusion-positive tumors may behave as lower grade, though individual outcomes vary.
CRTC3–MAML2 fusion: Less commonly, MAML2 fuses with CRTC3 rather than CRTC1. This rarer fusion appears to activate a similar pathway and supports the same diagnosis. It is reported in a smaller subset of breast cases.
HRAS mutations: Some tumors that lack MAML2 fusions show activating changes in HRAS. These have been described in mucoepidermoid tumors and in a subset of breast cases, but current evidence is limited. When present, they may point to different biology than fusion-positive disease.
Germline predisposition: A consistent link with inherited breast cancer genes (such as BRCA1/2) has not been shown for this tumor type. Most Breast mucoepidermoid carcinoma seems to arise from changes acquired in the tumor, not inherited at birth. Germline testing is typically guided by personal and family history rather than this diagnosis alone.
Lifestyle risk factors
Evidence specific to breast mucoepidermoid carcinoma is sparse, so most insights come from broader breast cancer research. In that context, lifestyle risk factors for Breast mucoepidermoid carcinoma are presumed to mirror those for other breast cancers. Modifying daily habits may help lower risk and support outcomes alongside medical care.
Regular drinking raises breast cancer risk by increasing estrogen and promoting DNA damage. Risk appears dose-dependent, so less is better for rare subtypes like this as well.
Tobacco use is linked to higher risk for several breast cancer subtypes and may worsen treatment tolerance. Quitting can reduce inflammation and support recovery if cancer develops.
Higher body fat, especially after menopause, increases breast cancer risk via hormonal and inflammatory pathways. Weight management may also help reduce recurrence risk and treatment complications.
Low activity levels are associated with higher breast cancer risk and poorer outcomes. Regular moderate exercise can improve metabolic health and may enhance therapy tolerance.
Risk prevention
Breast mucoepidermoid carcinoma is rare, and there’s no guaranteed way to prevent it, but the same steps that lower overall breast cancer risk are likely helpful. Focus on everyday habits and personalized screening based on your age and family history. Prevention works best when combined with regular check-ups. If you notice new breast changes, timely evaluation can also reduce the chance of complications.
Follow age- and risk-based mammogram plans, and ask if you need earlier or more frequent imaging. Screenings and check-ups are part of prevention too.
Keep alcohol to no more than one drink a day, and fewer is better. Cutting back lowers breast cancer risk.
Aim for at least 150 minutes of moderate exercise or 75 minutes of vigorous activity each week, plus strength training. Regular movement helps balance hormones and weight.
Work toward a steady, healthy weight through balanced eating and activity. Avoiding weight gain, especially after menopause, can lower risk.
Transmission
Breast mucoepidermoid carcinoma is not contagious—it cannot be transferred between people and is not infectious. It does not spread through everyday contact, kissing, sex, or shared objects.
Regarding how breast mucoepidermoid carcinoma is inherited, there is no genetic transmission of this cancer; most cases arise from gene changes that occur only in the breast cells during a person’s life. Having a family history of breast cancer can influence general risk, but this rare subtype is typically not linked to inherited cancer syndromes.
When to test your genes
Consider genetic testing if you were diagnosed with breast mucoepidermoid carcinoma at a young age, have multiple or rare tumors, or a strong family history of breast, ovarian, pancreatic, or prostate cancers. Testing can guide surveillance, treatment options, and family risk. Ask your care team about germline and tumor profiling.
Diagnosis
Breast mucoepidermoid carcinoma is rare, so most people first notice general breast changes such as a new lump, tenderness, or a feeling that one area is different from the rest. Doctors usually begin with a breast exam and imaging, then move to a biopsy to confirm the exact type. Because this tumor can look like other breast cancers, the diagnosis relies on careful lab review of the tissue. If you’re wondering how breast mucoepidermoid carcinoma is diagnosed, it typically involves several steps that build on each other to provide clarity.
A clinician checks for a firm or tender lump, skin dimpling, or nipple changes. Findings guide which tests come next.
Detailed X‑rays look for a mass or new calcifications. Imaging can suggest cancer but cannot confirm the specific subtype.
Sound waves help distinguish a solid mass from a fluid‑filled cyst. It also helps target the exact area for biopsy.
MRI can map the size and extent of the tumor, especially in dense breast tissue. It helps plan surgery but still needs a biopsy for confirmation.
Stages of Breast mucoepidermoid carcinoma
Staging for breast mucoepidermoid carcinoma follows the standard breast cancer system, from stage 0 to stage IV. Early symptoms of breast mucoepidermoid carcinoma often mirror other breast cancers—like noticing a new lump—but stage is based on tumor size, lymph nodes, and whether it has spread. Different tests may be suggested to help define the stage, including breast imaging, lymph node assessment, and sometimes scans of other areas.
Stage 0
In situ: Abnormal cells are confined to the milk ducts with no invasion into nearby tissue. Often found on screening with no lump noticed. Treatment aims to prevent future spread.
Stage I
Small localized: The tumor is up to 2 cm (about 0.8 in) with no lymph nodes involved or only tiny traces found. Outcomes are usually favorable with local treatment and sentinel lymph node biopsy.
Stage II
Larger or nodes: The tumor measures 2–5 cm (about 0.8–2 in) and/or a few nearby lymph nodes are involved. Breast mucoepidermoid carcinoma at this stage may need combined treatments such as surgery plus radiation or medicines.
Stage III
Locally advanced: The tumor is larger than 5 cm (>2 in), involves many lymph nodes, or affects the skin or chest wall. It has not spread to distant organs. Care often includes several steps, like medicines before surgery to shrink the tumor.
Stage IV
Metastatic spread: Cancer has spread to distant organs such as bone, lung, or liver. The focus is on control, symptom relief, and maintaining quality of life. Treatments are typically whole‑body medicines, with targeted options when available.
Outlook and prognosis
Looking at the long-term picture can be helpful. For most people with breast mucoepidermoid carcinoma, the outlook depends on how early it’s found, the tumor’s grade under the microscope, and whether it has spread to lymph nodes. Low‑grade tumors tend to grow slowly and are often cured with surgery, sometimes followed by radiation if margins are close. High‑grade tumors act more aggressively and are treated more like other invasive breast cancers, usually with a combination of surgery, radiation, and systemic therapy.
Doctors call this the prognosis—a medical word for likely outcomes. In published case series, low‑grade breast mucoepidermoid carcinoma has a favorable prognosis with high survival rates and a low risk of returning after complete removal. High‑grade disease carries a higher chance of recurrence or spread, so follow‑up is more intensive. Mortality is uncommon in low‑grade cases; when deaths occur, they are usually linked to high‑grade features or distant metastases.
Everyone’s journey looks a little different. Your personal risks are shaped by tumor stage at diagnosis, grade, surgical margins, lymph node findings, hormone or HER2 status, and overall health. If you’re wondering about early symptoms of breast mucoepidermoid carcinoma, they often mirror other breast cancers—a new lump, breast firmness, or a change on screening—so standard breast screening and prompt evaluation still matter. Talk with your doctor about what your personal outlook might look like.
Long-term effects
Breast mucoepidermoid carcinoma is rare, and the long-term picture depends largely on the tumor’s grade and whether lymph nodes are involved. Many living with this diagnosis do well after surgery, especially when the tumor is low grade and caught early. Long-term effects vary widely, with higher-grade cancers carrying a greater chance of coming back or spreading. Regular follow-up helps catch changes early and supports timely treatment if needed.
Low-grade breast mucoepidermoid carcinoma often grows slowly and is linked with high long-term survival. High-grade tumors behave more aggressively and carry higher risks over time.
The cancer can return in the breast or surgical area, especially with high-grade tumors or close margins. Most relapses happen in the first 5 years, though later events can occur.
Nodes are less often affected in low-grade breast mucoepidermoid carcinoma but can be involved. When nodes are positive, the chance of spread and recurrence increases.
High-grade tumors can spread to lungs, bones, or liver. Low-grade tumors rarely travel beyond the breast over the long term.
How is it to live with Breast mucoepidermoid carcinoma?
Living with breast mucoepidermoid carcinoma can feel like stepping into unfamiliar territory, because it’s a rare breast cancer and information may be harder to find. Day to day, most people focus on recovery from treatment—managing fatigue, tenderness or tightness in the breast or chest wall, changes in body image, and the rhythm of follow-up visits—while making space for work, family, and the activities that restore energy. Loved ones are often deeply involved, offering rides, help with household tasks, and emotional support, but they may also need clear cues about when you want practical help versus quiet company. Over time, many find a new routine that blends vigilance—keeping up with checkups and reporting new symptoms—with confidence in their care plan and the things that keep life meaningful.
Treatment and drugs
Treatment for breast mucoepidermoid carcinoma usually centers on surgery to remove the tumor, with the goal of clear margins and preserving breast shape when possible. Depending on the tumor grade and lymph node findings, doctors may add radiation therapy to lower the risk of the cancer coming back in the breast, and sometimes chemotherapy for higher-grade or more advanced disease. Hormone-blocking therapy and HER2-targeted drugs are generally not helpful for breast mucoepidermoid carcinoma unless testing shows the tumor has those targets. Not every treatment works the same way for every person, so your team will tailor the plan based on tumor features, stage, your overall health, and your preferences. Ask your doctor about the best starting point for you.
Non-drug treatment
Non-drug care for breast mucoepidermoid carcinoma focuses on removing the tumor, aiming to prevent local return, and supporting recovery and daily function. Beyond prescriptions, supportive therapies can round out treatment so you heal well and stay active during and after care. Even if early symptoms of breast mucoepidermoid carcinoma are subtle, surgery and targeted radiation are often central, while rehabilitation, lymph care, and counseling help with long-term quality of life.
The surgeon removes the tumor with a small rim of healthy tissue to keep the breast shape. Lab checks on the margins guide whether more treatment is needed.
The whole breast is removed when the tumor is large, widespread, or margins would be hard to clear. Some choose immediate or delayed reconstruction to restore shape.
A few key lymph nodes are sampled to check if cancer has spread. This helps avoid removing many nodes when it isn’t necessary.
More lymph nodes are removed if tests show spread or if nodes feel involved. It can raise lymphedema risk, so it’s used only when clearly needed.
Your genes may have an impact on how drugs work for you
Genes can affect how your body processes cancer drugs—some people break down medicines quickly and need higher doses, while others metabolize them slowly and face more side effects. For breast mucoepidermoid carcinoma, doctors may use genetic testing to guide targeted therapies and dosing.
Pharmacological treatments
Because breast mucoepidermoid carcinoma is rare, drug choices are usually guided by standard breast cancer practice and by the tumor’s features (hormone receptors, HER2 status, PD‑L1, and any BRCA gene changes). Systemic therapy options for breast mucoepidermoid carcinoma may include chemotherapy, endocrine (hormone) therapy, targeted drugs, and, in select cases, immunotherapy. Not everyone responds to the same medication in the same way. Your care team will tailor treatment based on stage, biology, prior treatments, and your overall health.
Doxorubicin plus cyclophosphamide, followed by paclitaxel or docetaxel, is a common backbone for higher‑risk early disease or metastases. This approach is often adapted for breast mucoepidermoid carcinoma when chemotherapy is indicated.
Carboplatin or cisplatin may be paired with paclitaxel or docetaxel, especially for triple‑negative patterns or aggressive disease. This can be considered for breast mucoepidermoid carcinoma with high‑risk features.
Tamoxifen, or aromatase inhibitors such as anastrozole, letrozole, or exemestane, treat estrogen‑ or progesterone‑receptor–positive tumors. Ovarian suppression with goserelin may be added for premenopausal adults to enhance benefit.
Trastuzumab, often with pertuzumab, is used for HER2‑positive disease; ado‑trastuzumab emtansine (T‑DM1) may be used if cancer remains after pre‑surgery chemo. Ask your doctor why a specific drug was recommended for you.
Genetic influences
Most cases of breast mucoepidermoid carcinoma appear to come from genetic changes that develop only in the tumor, not from genes you’re born with. It’s natural to ask whether family history plays a role. In many tumors, pathologists find a specific DNA swap that joins two genes—often involving MAML2 (the CRTC1–MAML2 fusion)—which can act like a stuck-on growth signal inside the cancer cells. This fusion is an acquired, or somatic, change that sits in the tumor but not the rest of the body, so it isn’t passed down to children. Inherited mutations such as BRCA1 or BRCA2 raise the overall chance of breast cancer, but they haven’t been shown to specifically increase the inherited risk of breast mucoepidermoid carcinoma. Testing the tumor for MAML2 and related markers can help confirm the diagnosis and may offer clues to outlook, while inherited genetic testing is usually guided by your personal and family history of breast cancer rather than this rare subtype.
Is Breast mucoepidermoid carcinoma genetic?
Genetics play a meaningful role in breast mucoepidermoid carcinoma, but data are limited due to its rarity. Tumor changes, like MAML2 gene fusions, are reported and may guide diagnosis and prognosis. Inherited risk appears low; most cases seem sporadic.
Pharmacogenetics—how genetics influence drug effects
Treatment for Breast mucoepidermoid carcinoma is increasingly shaped by the tumor’s own biology rather than a single standard plan. Testing often looks for a MAML2 gene fusion seen in salivary‑type tumors; it can help confirm the diagnosis and may signal a less aggressive course, but it isn’t yet a direct drug target. Routine breast cancer markers still guide therapy: if the tumor is hormone‑receptor positive, endocrine medicines may help; if HER2 is amplified, HER2‑targeted drugs are considered; however, many breast mucoepidermoid carcinomas are negative for these and rely on chemotherapy or, in select cases, immunotherapy. Some inherited changes, such as BRCA1 or BRCA2 variants, can open options like PARP inhibitors or make platinum chemotherapy more relevant, especially if the cancer behaves like triple‑negative disease. Genetic testing can sometimes identify how your body processes certain medicines, for example checking DPYD before using 5‑fluorouracil or capecitabine to reduce severe side effects. Rare, targetable fusions (like NTRK) are uncommon but worth looking for in advanced disease, because tumor‑agnostic medicines may be an option when present.
Interactions with other conditions
People with breast mucoepidermoid carcinoma often manage it alongside other health issues, which can influence testing and treatment choices. Because early symptoms of breast mucoepidermoid carcinoma can look like common breast changes—a new lump or tenderness—benign conditions such as cysts or mastitis may briefly cloud the picture on exams and imaging. Doctors call it a “comorbidity” when two conditions occur together. Heart disease, diabetes, or kidney problems can affect which medicines are safest, recovery after surgery, and whether radiation or chemotherapy is recommended. If treatment does include chemotherapy, immune‑suppressing effects can raise infection risk, especially for those already living with chronic infections or taking steroids for another illness. Prior chest radiation for a different cancer, or ongoing therapies that interact with the heart, may also shape the plan for breast mucoepidermoid carcinoma, so teams usually coordinate closely across specialties.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described stubborn breast lumps that behaved differently from the usual patterns. Families and communities once noticed patterns of slow‑growing masses in the breast that didn’t fit neatly into familiar categories, sometimes returning after treatment or showing mixed features under the microscope. Before modern testing, early surgeons relied on look and feel, and these unusual tumors were grouped with other breast cancers, even though they didn’t act quite the same.
First described in the medical literature as a rare breast tumor with a “salivary‑type” appearance, breast mucoepidermoid carcinoma drew attention because it contained a mix of cell types—some making mucus and others looking more like skin‑type cells. Pathologists initially recognized it by how the tissue looked when stained and viewed under a microscope. Over time, descriptions became more precise as staining techniques improved, allowing doctors to separate it from more common breast cancers and from benign mucus‑producing changes.
As medical science evolved, specialists noticed that breast mucoepidermoid carcinoma has close relatives in the salivary glands, where mucoepidermoid tumors are more common and better studied. This connection helped clinicians borrow insights about grading and behavior, then adapt them to the breast. With each decade, larger case collections refined the picture: some tumors were low‑grade and slow, while others were higher‑grade and more aggressive. These differences explained why outcomes varied so widely in earlier reports.
Advances in imaging and surgery in the late 20th century improved detection and local treatment, while standardized pathology reports brought clearer terminology. Later, molecular tests began to reveal genetic fingerprints seen in some salivary‑type tumors, offering clues—but not yet a single defining marker—for the breast form. From early theories to modern research, the story of breast mucoepidermoid carcinoma has moved from scattered case notes to a more consistent understanding of how to diagnose and manage it.
Not every early description was complete, yet together they built the foundation of today’s knowledge. Today, clinicians recognize breast mucoepidermoid carcinoma as uncommon and diverse in behavior, with care tailored to the tumor’s grade and features. Knowing the condition’s history helps explain why careful pathology review still plays such an important role, and why recommendations may differ from those for more typical breast cancers.