BACKGROUND: Sarcomas can develop de novo or secondary to radiotherapy after or during breast cancer treatment. Diagnosis can be challenging, as such, a sarcoma is often missed on routine follow-up imaging and often presents with dermatologic findings.

CASE REPORT: Here, we present a case of a 45-year-old female who developed spindle cell sarcoma on her neck, which was mimicking supraclavicular lymph node metastasis of breast cancer.

CONCLUSIONS: Based on our report, we recommend a tissue biopsy with an immunohistochemistry profile when a mass suspicious for metastasis is found in patients with breast cancer.

Keywords: Breast Neoplasms, Sarcoma, Diagnosis, Differential, Neck, Neoplasms, Second Primary, Soft Tissue Neoplasms