Guideline Summary for Evaluation and Management of Non‑Tender Sternal Enlargement After Modified Radical Mastectomy

Clinical Presentation

Most local recurrences after mastectomy present as clinically detectable chest‑wall masses, and the absence of pain does not exclude malignancy. 1, 2

Node‑positive disease at initial diagnosis is associated with an 11 % recurrence rate at 5 years, versus 6.7 % for node‑negative disease. 3
High‑grade tumor, lymphovascular invasion, and non‑luminal tumor type at original diagnosis are high‑risk features for recurrence. 3
Primary tumor size greater than 5 cm and positive surgical margins increase the risk of recurrence. 3, 4
Age younger than 35–40 years at initial diagnosis is an additional risk factor. 4

Fat necrosis is the most common benign finding after breast surgery and may appear years after the procedure. 5
Seroma, hematoma, or chronic inflammatory changes are possible but are less likely five years after surgery. 5

Biopsy is mandatory for any suspicious sternal‑region mass to confirm recurrence versus a benign etiology and to assess hormone‑receptor and HER2 status; ultrasound guidance facilitates safe sampling of parasternal masses. 3

Isolated locoregional recurrence without distant metastases can be treated with curative intent using surgery, radiation therapy, and systemic therapy. 3
True sternal metastases are rarely solitary and usually occur with multiple skeletal lesions elsewhere. 3
When sternal invasion is present, selected patients can undergo resection with excellent outcomes. 3
Invasion of the sternum into thoracic structures indicates a poorer prognosis, yet aggressive local therapy may still achieve long disease‑free survival. 3

The modified radical mastectomy preserves the pectoralis major muscle and does not involve the sternum, distinguishing it from procedures that require sternotomy or chest‑wall resection. 6

Local‑regional recurrence after mastectomy occurs at a rate of 1–2 % per year, with a constant incidence of local failure from years 2 through 8 post‑treatment. 7

MRI with T1‑weighted fat‑suppressed gadolinium sequences is superior to CT for identifying residual or recurrent tumor involving chest‑wall and parasternal structures. 6
PET‑CT demonstrates high diagnostic accuracy for sternal involvement, with a sensitivity of ~91 % and specificity of ~97 % when infection or tumor recurrence is suspected. 6, 8

Ultrasound should be the initial imaging modality for any palpable mass in the post‑mastectomy chest wall, including areas adjacent to the sternum, to guide further work‑up and possible tissue diagnosis. 9