What causes a new lump or swelling?

Swelling can occur when immune tissue reacts to infection or irritation. A cyst contains fluid or other material, while a benign growth is an organised collection of cells that does not invade nearby tissue. Tumours can arise in soft tissue, skin, or organs and may feel different depending on their depth and location.

Cancer-related causes vary by body site and can include soft tissue sarcoma, Merkel cell carcinoma, penile cancer, vulvar cancer, childhood cancer, or cancer of unknown primary. A new lump is a presentation of these conditions in some people; it does not establish that the lump is cancerous.

Note where the lump is, when you first noticed it, whether it is growing, and whether the skin is warm, red, or broken. Mention fever, pain, night sweats, unexplained weight change, or a recent injury. A clinician may examine the area and arrange imaging or a tissue sample.

Do not squeeze, puncture, or repeatedly massage a new lump. Arrange review when it persists, enlarges, returns, feels hard or fixed, or has no clear explanation.

Arrange prompt review for a lump that is growing, persistent, firm, deep, or associated with unexplained symptoms. Seek urgent care for rapidly increasing swelling, severe pain, heavy bleeding, skin breakdown with spreading redness, or difficulty breathing or swallowing.

What structures could be causing this lump? Does its location or growth pattern call for imaging? Would a needle or tissue sample help? Could an infection or injury explain it? When should I return if it does not change or if new symptoms appear?