Breast Cancer Molecular Subtypes and Skeletal Metastases Patterns on Bone Scintigraphy

Inclusion Criteria:

• Patients of both sexes (females and males) with a confirmed histopathological diagnosis of breast cancer, including all major histological types: Invasive Ductal Carcinoma (IDC), Invasive Lobular Carcinoma (ILC), other mixed or less common epithelial variants.
• Patient's age ranging from 18 to 80 years.
• Available immunohistochemical (IHC) profiles from the primary breast tumor biopsy or surgery, covering all molecular subtypes including; Luminal A: (ER-positive, PR-positive, HER2-negative, and low Ki-67 index). Luminal B: (ER-positive, PR-variable, HER2-variable "either positive or negative", and high Ki-67 index). HER2-enriched: (ER-negative, PR-negative, and HER2-positive). Triple-Negative breast cancer (TNBC): (no ER, PR or HER2 expression).
• Patients referred for bone scintigraphy as part of initial staging, follow-up, or due to clinical suspicion of bone metastasis.

Exclusion Criteria:

• Patients with other primary malignancies (to avoid confusion regarding the origin of bone metastases).
• Patients with incomplete medical records or unavailable immunohistochemical data.
• Pregnant female patients.
• Patients aged under 18 years old.