A rare and notoriously deceptive cancer of the breast’s blood vessels has been documented in a 51-year-old postmenopausal woman who remained disease-free for more than five years after a diagnosis that nearly slipped through the cracks. The case, published in the open-access journal Cancer Reports, describes a primary breast angiosarcoma—a malignancy arising from the endothelial cells that line blood vessels—that accounted for only about 0.04 percent of all primary malignant breast tumors. Because these tumors overwhelmingly strike younger women between the ages of 20 and 40, and because postmenopausal angiosarcoma of the breast is almost always a secondary cancer triggered by earlier radiation therapy, the appearance of a primary tumor in a woman of this age is exceptionally unusual. The clinical team’s account offers a detailed lesson in how easily such a tumor can masquerade as an ordinary benign lump, and how a combination of surgical caution, pathological consultation, and multidisciplinary decision-making rescued the diagnosis.
The patient’s story began in September 2019, when she first noticed a small, mobile mass in her left breast measuring roughly 2 by 1 by 1 centimeters. The lump caused no tenderness, no skin changes, and no nipple discharge, so she initially ignored it. Two months later, at another hospital, mammography and breast color Doppler ultrasound both classified the lesion as Breast Imaging Reporting and Data System category III—a designation implying a probably benign finding with less than a 2 percent risk of malignancy—and recommended routine follow-up. Over the following three months, however, the mass grew dramatically, reaching approximately 4 by 3 by 2 centimeters and occasionally becoming painful. That rapid enlargement prompted her admission to the reporting hospital in March 2020, where physical examination found a smooth, moderately firm, mobile mass without skin ulceration, nipple retraction, or enlarged lymph nodes in the armpits.
The imaging workup revealed a striking contradiction. Mammography at the outside hospital had graded the lesion BI-RADS 3, but repeat ultrasound at the new institution upgraded it to BI-RADS 4A, indicating a small but real suspicion of malignancy of roughly 2 to 10 percent. The ultrasound showed a solid, irregular, lobulated mass at the 11 o’clock position of the left breast, containing strip-like blood flow signals with low-resistance arterial waveforms—a vascular pattern that would later prove telling. Chest computed tomography confirmed a mound-shaped mass in the upper inner quadrant with an unclear boundary on plain scan. Meanwhile, laboratory results were entirely unremarkable: blood counts, liver and kidney function, and coagulation were normal, and the tumor markers CEA, CA 15-3, CA 125, and CA 19-9 all sat comfortably within reference ranges. The team noted that breast angiosarcomas frequently produce negative results on routine malignant tumor markers, rendering these tests of extremely low diagnostic value in such cases.
Reconciling the discordant imaging grades against current standards proved decisive in shaping the diagnostic pathway. According to the fifth edition of the American College of Radiology BI-RADS criteria, the 2024 National Comprehensive Cancer Network breast guidelines, and the 2021 Chinese Society of Breast Surgery fibroadenoma guideline, the combined clinical and imaging picture did not meet formal indications for contrast-enhanced breast MRI, bone scintigraphy, or percutaneous core needle biopsy. Those tools are reserved for high-risk patients, radiologically indeterminate lesions with definite malignant suspicion, or preoperative staging of confirmed cancers—not for discordant low-grade BI-RADS 4A lesions accompanied by benign mammographic findings. The clinicians therefore concluded the lesion was highly suggestive of a benign fibroadenoma and recommended elective surgical resection, a decision that conformed to guidelines but, as they later acknowledged, failed to account specifically for the lesion’s rapid growth.
Surgery took place on March 11, 2020, under general anesthesia, and it was here that the case pivoted. Intraoperative frozen section pathology suggested a spindle cell tumor tending toward a vascular origin, with definitive classification awaiting immunohistochemistry. Because the team had rarely encountered such lesions, and because committing to a radical operation on an uncertain diagnosis carried obvious risks, they consulted the patient’s family and made the unusual decision to temporarily suspend the surgery. Final pathology returned on March 17: the excised nodule, about 3.5 by 2.5 by 1.8 centimeters, was packed with anastomosing slit-like vascular channels infiltrating breast lobules and fat, lined by a single layer of endothelial cells showing mild nuclear atypia and occasional mitoses. Immunohistochemistry showed strong positivity for the endothelial markers CD34, CD31, and FLT-1, along with vimentin and smooth muscle actin, while epithelial markers EMA and broad-spectrum cytokeratins were negative. The Ki-67 proliferation index was 25 percent. The diagnosis was low-grade angiosarcoma.
To be certain, the slides were sent for outside consultation at a higher-level hospital, which returned on March 20 with a confirmatory and slightly more concerning picture: part of the tumor showed the mild, well-formed vascular pattern, but other areas were solid, densely cellular, and pleomorphic with mitotic figures, extensive hemorrhage, and necrosis. The consultants recommended optional molecular testing for c-Myc, KDR, and VEGFR2—markers mainly useful for distinguishing primary from radiation-associated secondary angiosarcoma—though the team ultimately judged these unnecessary given the clear histopathological diagnosis. After a hospital-wide multidisciplinary team discussion, the patient underwent completion resection of the remaining left breast tissue plus sentinel lymph node biopsy on March 23. Frozen section confirmed an R0 resection with clear microscopic margins and no sentinel node metastasis, and final pathology found no residual cancer in the surrounding breast, nipple, skin, or basal margin, with zero of three sentinel nodes involved.
The staging and treatment decisions reflected the peculiar biology of this tumor. Under the eighth edition of the AJCC staging system, the disease was classified as stage I (T1N0M0). Unlike conventional breast carcinoma, which spreads chiefly through lymphatic channels, primary breast angiosarcoma metastasizes predominantly through the bloodstream, seeding the liver, lungs, bone, and brain early, while regional lymph node involvement is extremely rare. Routine axillary lymph node dissection is therefore not recommended, and the team performed only a sentinel node biopsy for accurate staging, sparing the patient unnecessary surgical trauma. Beginning April 3, 2020, she received eight cycles of adjuvant chemotherapy—four of doxorubicin plus cyclophosphamide followed by four of paclitaxel—completed without significant adverse reactions by the end of July 2020.
The prognosis data assembled in the report underscore why vigilance matters. Secondary angiosarcoma of the breast, which typically arises after radiotherapy for breast cancer or in the setting of chronic lymphedema known as Stewart-Treves syndrome, carries a five-year overall survival of roughly 38 percent with a recurrence-free survival of about 43 months. Primary breast angiosarcoma fares somewhat better, with a five-year overall survival near 49 percent and recurrence-free survival of about 44 months, with outcomes tied to stage, histological grade, and tumor size. Diagnosis remains the hardest part: mammography yields false negatives in roughly a third of patients because of dense glandular tissue, ultrasound lacks specificity despite showing heterogeneous masses and increased blood flow, and MRI—considered the most useful non-invasive modality—reveals heterogeneous signals and avid contrast enhancement reflecting the tumor’s rich vascularity. Core needle biopsy, the usual route to preoperative diagnosis, frequently returns false negatives because of bleeding risk and marked tumor heterogeneity, meaning most cases are only confirmed after surgery.
Emerging evidence is beginning to reshape treatment thinking for this orphan disease. A meta-analysis by Skarentzos and colleagues found that adjuvant chemotherapy significantly improved survival in primary breast angiosarcoma, with a hazard ratio of 0.11, while radiotherapy showed no survival benefit. Anthracycline-, ifosfamide-, and paclitaxel-containing regimens are considered the most effective, though the disease’s rarity means evidence rests on small series and case reports rather than large trials. Genomic research is opening new doors: the Angiosarcoma Project, a patient-partnered genomic study, has suggested that inhibitors of the phosphatidylinositol-3-kinase catalytic alpha subunit could become targeted therapeutic options, and next-generation sequencing may eventually identify actionable alterations in tumors like this one.
Follow-up tells the story’s encouraging end. The patient was re-examined at one, three, and six months after surgery, then roughly every six months, with breast ultrasound, chest CT, abdominal and urinary tract ultrasound, blood counts, and tumor markers. As of November 5, 2025—more than five years after her diagnosis—she showed no sign of local recurrence or distant metastasis. The authors argue their case carries three broader lessons: that a rapidly growing, benign-appearing breast mass in a postmenopausal woman deserves heightened suspicion even when guidelines do not mandate advanced imaging; that suspending surgery when frozen section reveals something unexpected can preserve diagnostic accuracy and prevent undertreatment; and that multidisciplinary collaboration, staged surgery, and guideline-conformant individualized therapy can deliver excellent long-term outcomes even in a cancer this rare and this easy to miss.
Subject of Research: Primary breast angiosarcoma diagnosis and treatment in a postmenopausal woman
Article Title: Primary Mammary Angiosarcoma in a Postmenopausal Woman: A Case Report
Article References: Liu, T., Xu, Y., Wang, Q., Yu, S., Lin, H., Ye, Z., Zheng, Z., Yang, C., & Hong, T. (2026). Primary Mammary Angiosarcoma in a Postmenopausal Woman: A Case Report. Cancer Reports, 9(9), Article e70653. https://doi.org/10.1002/cnr2.70653
Image Credits: AI Generated
DOI: 10.1002/cnr2.70653
Keywords: breast angiosarcoma, primary breast angiosarcoma, postmenopausal, BI-RADS, fibroadenoma, frozen section pathology, immunohistochemistry, CD31, sentinel lymph node biopsy, adjuvant chemotherapy, R0 resection, rare cancer
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Nathaniel Bowman. (September 24, 2026). Rare Breast Cancer That Hides as a Benign Lump Diagnosed in Postmenopausal Woman. Scienmag. https://scienmag.com/rare-breast-cancer-that-hides-as-a-benign-lump-diagnosed-in-postmenopausal-woman/
Nathaniel Bowman. “Rare Breast Cancer That Hides as a Benign Lump Diagnosed in Postmenopausal Woman.” Scienmag, 24 September 2026, https://scienmag.com/rare-breast-cancer-that-hides-as-a-benign-lump-diagnosed-in-postmenopausal-woman/. Accessed 24 September 2026.
Nathaniel Bowman. “Rare Breast Cancer That Hides as a Benign Lump Diagnosed in Postmenopausal Woman.” Scienmag. September 24, 2026. https://scienmag.com/rare-breast-cancer-that-hides-as-a-benign-lump-diagnosed-in-postmenopausal-woman/
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Tags: adjuvant chemotherapyBI-RADSbreast angiosarcomaBreast angiosarcoma diagnosis in postmenopausal womenCD31challenges in diagnosing rare breast cancersclinical features of primary breast angiosdeceptive benign breast lumpearly detection of rare breast tumorsfibroadenomafrozen section pathologyimmunohistochemistryimportance of pathological consultation in breast tumor diagnosislong-term survival in rare breast angiosarcomamalignant vascular tumors of the breastmultidisciplinary approach to breast cancer diagnosispostmenopausalpostmenopausal breast cancer case studyprimary breast angiosarcomaR0 resectionrare cancerrare primary breast blood vessel cancersecondary breast angiosarcoma after radiation therapysentinel lymph node biopsy
