Management of Malignant Psoas Syndrome From Breast Cancer: A Case Report.

Malignant psoas syndrome (MPS) is a cancer-related pain syndrome caused by the metastasis or direct invasion of malignant tumors into the psoas muscle. Breast cancer metastases to skeletal muscles, particularly the psoas muscle, are extremely rare, leading to a limited awareness of MPS. Even suspected MPS is rarely reported in the literature. Here, we present the first confirmed case of psoas muscle metastasis in a patient undergoing treatment for recurrent breast cancer who was diagnosed with MPS using computed tomography-guided biopsy. Early recognition of psoas muscle metastasis is essential for improving patient outcomes, particularly in maintaining daily functional activities.