# Occult Breast Cancer Presenting as Sternum Pain

## TL;DR

A 38-year-old woman with sternum pain was diagnosed with hidden breast cancer through imaging and lab tests, even without visible breast tumors.

## Contribution

This case highlights the use of PET-CT and IHC staining to identify occult breast cancer in the absence of visible breast lesions.

## Key findings

- A PET-CT scan showed increased FDG uptake in the sternum and internal mammary node.
- Immunohistochemical staining confirmed the diagnosis of occult breast cancer.

## Abstract

Bone metastasis has been reported in up to 70% of patients with advanced breast cancer. A total of 55.76% of skeletal metastases in women were derived from breast cancer. However, patients with bone metastasis from an occult primary breast cancer are a rare subset of patients. Here, we present the case of a 38-year-old woman who had sternum pain for 4 months. A whole-body PET-CT scan revealed that the FDG uptake of both the sternum and internal mammary node was significantly increased. The final diagnosis of occult breast cancer was established by immunohistochemical (IHC) staining, which is of great significance for identifying the origin of a metastatic tumor despite no visualized lesions of mammary glands.