An American woman is thought to be one of only nine known cases where a biopsy led to the cancer vanishing within a matter of weeks, and without any treatment being initiated.
It’s understood that a biopsy to diagnose a tumour in the woman’s arm triggered an immune response against the cancer, according to New Scientist.
The 59-year-old first discovered the lump when it was around 2cm wide, said doctors at Marshfield Clinic Health System in Wisconsin, USA, where she was treated, The Sun reports.
After it quickly grew in size and caused her pain, she sought medical attention and received a needle biopsy. The cancer cells were found to be aggressive and located between her skin and muscle in the connective tissue.
Rohit Sharma, who treated the woman at Marshfield, said her cancer was “likely to spread” when it was diagnosed.
But when she arrived to have the tumour surgically removed two weeks later, it had vanished, leaving doctors mystified.
According to Sharma, the tumour had “started to go down within three or four days” after the biopsy. To ensure the cancer had truly gone, a sample of surrounding tissue was examined and found to be cancer free.
The woman is now in remission having received no treatment.
“The timing of the biopsy and resolution suggests there’s an immune reaction occurring,” Sharma said.
It marks an incredibly uncommon occurrence, known as spontaneous regression (SR).
The case, discussed by six surgeons in the journal Cureus, was described as “an exceptionally rare biological event, estimated to occur in one out of every 60 000 to 100 000 cancer cases”.
It was dubbed an “extremely remarkable” case by one expert who concurred with Sharma.
Toby Lawrence, of the Centre for Immunology of Marseille-Luminy in France, said: “It really suggests some kind of immune activation in response to the injury of the biopsy, because it had extremely rapid effects on tumour growth.”
But he stressed the rarity of such a response from the body, and said such people may have a genetic disposition that causes their immune systems to respond in such a way.
However, such instances could lead to further breakthroughs in improving the general responses to cancer therapy – especially if there are further cases.
Study details
Spontaneous Regression of Soft Tissue Sarcoma Following Biopsy: A Case Report and Systematic Review of the Literature
Megan Gannon, Rachel Gabor, Anushka Gupta, Cheshta Gupta, Ruhi Shah, Rohit Sharma.
Published in Cureus on 15 April 2026
Abstract
Spontaneous regression (SR) of malignancy is a rare phenomenon offering unique insights into tumour-host immunology. In sarcomas, the incidence, triggers, and clinical implications of SR are poorly characterised. We aim to synthesise the published literature on SR in sarcoma and report a novel case from our institution where diagnostic biopsy triggered a complete pathological response (pCR).
We retrospectively reviewed one institutional case: a 59-year-old female with myxofibrosarcoma (MFS) who demonstrated significant regression following core needle biopsy. We subsequently conducted a descriptive systematic review in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, rather than a formal meta-analysis. PubMed, Embase, and Scopus were searched from inception to July 2025 for reports of SR in pathologically confirmed sarcomas without prior cytotoxic therapy.
In our institutional experience, the patient (59-year-old female, MFS) achieved complete clinical resolution within weeks of biopsy. Definitive wide excision revealed no viable tumour cells, confirming pCR. The systematic review identified 32 published studies describing 32 unique cases of SR in sarcoma. Diagnostic biopsy was the leading identified trigger (25%). Biopsy-associated regressions occurred more rapidly (median 0.9 months) compared to infection-associated (median five months) or spontaneous cases. Despite clinical regression, 75% of patients in the biopsy-triggered group underwent definitive surgical resection.
SR in sarcoma is frequently preceded by an immune-stimulating event, most notably biopsy. While SR provides in vivo evidence of host anti-tumour immunity, the potential for incomplete or transient response underscores that SR should not preclude definitive oncologic management. Ultimately, SR can be conceptualised as a “neoadjuvant immune boost” rather than a definitive cure. Wide surgical resection based on pre-regression tumour fields remains the standard of care to eradicate microscopic disease and ensure oncologic safety.
See more from MedicalBrief archives:
Spontaneous cancer regression, without treatment, rare – Canadian study