Retromammary Space

The retromammary space is an anatomical potential space located between the breast tissue and the underlying pectoral fascia covering the pectoralis major muscle. Although not a true anatomical cavity, this space allows for a degree of movement of the breast over the chest wall and serves as a critical surgical and radiological landmark. It is composed primarily of loose connective tissue and small amounts of fat, and its integrity is important in both benign and malignant conditions of the breast.

Location and Boundaries

• Anterior boundary: Deep surface of the breast parenchyma (posterior part of the glandular and fatty tissue)
• Posterior boundary: Pectoral fascia overlying the pectoralis major muscle
• Laterally: Continuous with axillary connective tissue spaces
• Superiorly and inferiorly: Extends from the second to the sixth ribs, along the height of the breast

Tissue Composition

The retromammary space is filled with loose areolar connective tissue and varying amounts of retromammary fat. This composition allows the breast some mobility relative to the chest wall — a clinically important characteristic in physical exams. Unlike the dense fibroglandular tissue of the breast proper, the retromammary space is non-glandular and lacks ducts or lobules.

Functional Significance

• Allows mobility of the breast over the pectoral muscles, especially in younger individuals
• Separates the glandular breast tissue from deeper chest wall structures, acting as a
• Helps define the posterior boundary of breast masses during palpation and imaging
• Used as a surgical access plane during mastectomy or implant placement

Role in Imaging

In breast ultrasonography and mammography, the retromammary space appears as a relatively hypoechoic (dark) area posterior to the dense breast tissue. It is used as a key landmark for:

• Assessing the posterior extent of a lesion
• Determining breast mobility
• Differentiating between superficial and deeply invasive tumors

Loss of definition or obliteration of this space may suggest tumor invasion into the chest wall or deep fixation of a malignancy.

Surgical Relevance

The retromammary space is frequently used as a dissection plane during:

• Total mastectomy: The entire breast is removed by separating it from the pectoralis major along this plane
• Subglandular breast implant placement: Implants may be placed within this space, anterior to the muscle
• Reconstructive surgery: The space allows for flap tunneling or placement of tissue expanders

Preservation of this plane is important for minimizing chest wall trauma and achieving clean surgical margins.

Clinical Significance

• Fixation of the breast: In advanced breast cancer, tumor invasion may cause loss of movement across this plane
• Deep infections: Rarely, infections or abscesses may track into this space and obscure normal anatomy
• Implant-related pathology: Capsular contracture or implant rupture may involve the retromammary zone and be detected through imaging or surgery