A 38-year-old woman who had been well all her life walked into an emergency department with a painful red lump in her left breast, about five centimeters across, firm and mobile. She was not breastfeeding. She felt otherwise fine. The team suspected an abscess, one of the most routine problems in breast surgery, and sent her home with antibiotics.
A week later she was back, no better. She was referred to general surgery, and during the operation to treat what everyone still assumed was an abscess, the surgeon found something else inside the cavity: a hard lesion with a necrotic center. Biopsies were taken. The pathology came back as metastatic large cell neuroendocrine carcinoma.
The case was published on August 28 in the New Zealand Medical Journal by Ally Yu, a University of Auckland medical student, surgical registrar Yijiao Wang, and breast and colorectal surgeon Eva Juhasz of Te Whatu Ora Waitematā in Auckland. To their knowledge, no one has previously reported neuroendocrine carcinoma presenting as a breast abscess.
Cancer Reaching the Breast from Somewhere Else Is Vanishingly Rare
Large cell neuroendocrine carcinoma is an aggressive high-grade cancer that most often starts in the lung, though it can arise in the gastrointestinal tract or pancreas. It typically spreads to the liver, bone, brain, and adrenal glands.
The breast is not on that list, and the numbers explain why the diagnosis is so easy to miss. Published estimates cited by the authors put metastases from neuroendocrine tumors at roughly 0.005 to 0.02 percent of all breast malignancies. When such metastases do occur, they have almost always presented as discrete masses or nodules, not as something that looks or feels infected.
There is a counterweight worth noting. A 2013 study in World Journal of Surgery argued that breast metastases from neuroendocrine tumors are more common than thought and represent a diagnostic pitfall. The rarity in the record may partly reflect how often the diagnosis is never made. A systematic review in Endocrine-Related Cancer published in 2025 has since gathered the reported cases of metastatic neuroendocrine neoplasms in the breast, a sign that clinicians are increasingly treating this as a pattern worth documenting rather than a one-off curiosity.
The distinction matters practically. A cancer that has spread to the breast from elsewhere is not breast cancer and is not treated like breast cancer. Getting the origin wrong sends a patient down the wrong treatment pathway entirely.
A Non-Smoker with a Smoker's Cancer
The patient profile was as unusual as the presentation. Large cell neuroendocrine carcinoma is strongly associated with tobacco exposure and, according to the literature the authors cite, typically affects men with a median age around 65. She was a 38-year-old lifelong non-smoker.
Her tumor markers were markedly elevated across the board, including chromogranin A, CA 15-3, CA 19-9, CA 125 and carcinoembryonic antigen. During further assessment, she was admitted with significant back pain. CT of the chest, abdomen and pelvis showed extensive disease: a large mass in the left upper lobe of the lung, with nodal, skeletal, pelvic and possible liver involvement. MRI confirmed the cancer had reached her lumbar spine. Even then, the primary tumor could not be definitively identified. A neuroendocrine tumor multidisciplinary meeting settled on stage IVB disease, most likely of lung origin.
The Molecular Result That Changed Her Treatment
Then came the twist that shifted her care. Molecular testing found an anaplastic lymphoma kinase rearrangement, an alteration usually associated with lung adenocarcinoma and only rarely reported in this cancer type.
Standard practice for advanced large cell neuroendocrine carcinoma is platinum-based chemotherapy similar to that used in small cell lung cancer, and she was initially waitlisted for carboplatin and paclitaxel. After the ALK result, she was started on the targeted drug alectinib instead. She had already completed palliative radiotherapy for her painful spinal metastases.
Reports of alectinib response in this tumor type are scarce in the literature. The New Zealand report does not describe long-term outcome, and the authors are direct that management guidelines for this cancer remain limited because of its rarity, with prognosis generally poor.
What Doctors Are Being Asked to Watch For
The authors' central argument is narrow and practical. Breast abscess is a common and usually benign condition routinely managed by general surgeons. Their case argues for a lower threshold to biopsy when an apparent abscess does not respond to treatment as expected.
That framing matters to readers, too, but it should not be taken as a reason for alarm. Most breast abscesses are exactly what they appear to be. Metastatic cancer presenting this way is, on current evidence, a first-of-its-kind report. The reasonable response is not fear of every breast infection but persistence when something is not resolving. A lump that fails to improve on antibiotics, or that keeps recurring, deserves follow-up rather than another round of the same treatment.
Anyone with a new breast lump, an unresolving breast infection or unexplained persistent back pain should be assessed by a clinician. Decisions about imaging and biopsy belong to the treating team.
Key Questions Answered
What was mistaken for an abscess? A metastatic deposit of large cell neuroendocrine carcinoma in the breast. It looked and behaved like a painful infected lump until surgery revealed a hard lesion with a necrotic center.
How rare is cancer spreading to the breast from another organ? Very rare. Published estimates put metastases from neuroendocrine tumors at roughly 0.005 to 0.02 percent of all breast malignancies.
Why was her case unusual beyond the presentation? This cancer is strongly linked to smoking and typically affects men around age 65. She was a 38-year-old lifelong non-smoker.
What did the molecular testing change? An ALK rearrangement was found, which is uncommon in this tumor type. Her planned chemotherapy was replaced with the targeted drug alectinib.
Does this mean breast abscesses are dangerous? No. Breast abscesses are common and usually straightforward. This appears to be the first reported case of neuroendocrine carcinoma presenting this way.
What should someone do if a breast lump is not improving? Go back to a clinician rather than repeating the same treatment. An apparent abscess that does not respond as expected warrants further assessment.
