A soft tissue mass is an abnormal lump or growth that develops in the non-bony, non-organ structures of the body. These masses can occur anywhere from the skin’s surface down to the deep layers of muscle and connective tissue. Understanding what a soft tissue mass is and how doctors determine its nature can help clarify the situation.
Defining Soft Tissue and Mass Formation
Soft tissue is an umbrella term for the structures that connect, support, and surround the internal organs and bones of the body. These components include fat, muscle, tendons, ligaments, fascia, nerves, and blood vessels. Soft tissue is distinct because it is not hardened by the processes of calcification or ossification, which create bone and teeth.
A “mass” forms when there is an abnormal accumulation or growth of cells or fluid within this soft tissue framework. This formation occurs through one of two primary mechanisms: neoplastic or non-neoplastic processes. Neoplastic masses involve the uncontrolled and excessive multiplication of cells, often resulting in a solid growth.
Non-neoplastic masses are not caused by abnormal cell growth but by other issues like inflammation, trauma, or fluid collection. Examples include hematomas, which are collections of clotted blood after an injury, or abscesses, which are localized pockets of pus from an infection.
The Spectrum of Soft Tissue Masses
Soft tissue masses span a wide spectrum, ranging from common, harmless lumps to rare, serious growths. The majority of these masses are benign, meaning they are non-cancerous and do not spread to other parts of the body. Benign masses are estimated to occur at least ten times more frequently than their malignant counterparts.
Common benign examples include lipomas, which are slow-growing tumors made of fat cells, and cysts, which are fluid-filled sacs. These typically grow slowly, are often small, and may feel soft or squishy to the touch. While they can sometimes cause pain by pressing on a nerve, benign masses generally remain localized.
Malignant soft tissue masses are known as sarcomas, and they are capable of invading surrounding tissue and spreading (metastasizing) to distant sites in the body. These growths are more likely to be found deeper in the tissue, be larger than five centimeters, and grow at a rapid rate. Sarcomas are also more likely to be painless initially, though pain can develop as they grow and compress nerves or other structures.
How Doctors Determine the Nature of the Mass
The process of investigating a soft tissue mass begins with a detailed physical examination and medical history. The doctor will assess the mass’s size, depth, consistency (soft or firm), and mobility within the surrounding tissue. A mass that is large, fixed to underlying structures, and deep beneath the fascia raises suspicion and prompts further investigation.
Imaging studies are the next step, with Ultrasound often used as the first line of evaluation. Ultrasound uses sound waves to determine if the mass is solid, suggesting a tumor, or cystic, meaning it is fluid-filled and likely benign. It also provides information on the mass’s size, borders, and blood flow.
Magnetic Resonance Imaging (MRI) is considered the preferred method for detailed evaluation of a concerning soft tissue mass. An MRI provides exceptional detail of the soft tissues, clearly mapping the mass’s exact size and its relationship to nearby structures like nerves and vessels. This detailed mapping is performed before a biopsy to ensure proper planning should the mass require surgical removal.
The definitive step to determine if a soft tissue mass is benign or malignant is the biopsy. This procedure involves taking a small sample of tissue from the mass, typically through a fine-needle aspiration or a core needle biopsy. The collected tissue is then examined by a pathologist under a microscope to identify the cell type and confirm whether the growth is non-cancerous or cancerous.