Occult breast carcinoma presenting as isolated vertebral metastasis with negative PET-CT but detected on contrast-enhanced MRI: A case report.

Occult breast cancer (OBC) is a rare subtype of breast malignancy defined by histologically proven metastasis without a clinically or radiologically detectable primary tumor. We report the case of a 45-year-old woman who presented with chronic lower-back pain and was found to have isolated vertebral metastasis without axillary involvement-an uncommon initial manifestation. Fluorodeoxyglucose (FDG) PET-CT failed to identify a primary lesion, whereas contrast-enhanced breast MRI (CE-MRI) demonstrated a subtle area of architectural distortion, later confirmed as infiltrating lobular carcinoma on biopsy. This case highlights the diagnostic limitations of PET-CT in tumors with low FDG avidity, such as invasive lobular carcinoma, and underscores the superior sensitivity of CE-MRI in detecting occult breast cancers.