TY  - JOUR
T1  - Tarlatamab Treatment for Metastatic Small Cell Neuroendocrine Carcinoma of the Breast: A Case Report 
AU  - Poljak, Dijana
AU  - Zhang, Huina
JF  - Journal of Clinical and Translational Pathology
VL  - 
IS  - 000
SN  - 2771-165X
SP  - 
EP  - 
Y1  - 2026-09-30
DO  - 10.14218/JCTP.2026.00031
UR  - https://www.xiahepublishing.com/2771-165X/JCTP-2026-00031
AB  - Background 
Since their first inception, neuroendocrine neoplasms of the breast have undergone many iterations of classification and definition. Taken together with their extremely low incidence, the ever-evolving landscape has made diagnosis, treatment, and research exceedingly challenging.
Case presentation
Our patient is a 45-year-old female who had a breast mass with clinical workup favoring a breast primary. A diagnosis of small cell carcinoma was established after an extensive clinical and pathologic workup. The mass did not respond to traditional neoadjuvant platinum-based chemotherapy, and she underwent a total mastectomy. Shortly thereafter, imaging revealed widely metastatic disease involving the brain, chest, abdomen, and pelvis. She received whole-brain radiation and, given the previous lack of response to chemotherapy, was recommended to try off-label tarlatamab. To date, with a short-term follow-up of 5 months, after whole-brain radiotherapy administered concurrently with the first cycle of tarlatamab, subsequent imaging showed near-complete radiographic resolution of extracranial metastatic disease, while the brain lesions also showed radiographic resolution on follow-up MRI.
Conclusions
We report the novel and preliminary use of tarlatamab in a patient with small cell neuroendocrine carcinoma of the breast, with short-term follow-up. We also discuss the most critical challenges associated with this rare pathologic diagnosis and the important elements to consider to ensure that metastatic disease is excluded.