Small lump under the skin on the back: what to know

A soft lump that moves beneath the skin may be a fatty growth, while a round lump with a pore or surface opening may be a cyst. Pain, warmth, redness, and drainage suggest inflammation or infection; [Boils](/conditions/boils/) are one possible skin presentation. The broader symptom guide is [Skin Lumps](/symptoms/skin-lumps/). A changing scab, sore, or bleeding surface should be examined, but a back lump alone does not establish [Basal Cell Carcinoma](/conditions/basal-cell-carcinoma/).

Ask someone you trust to photograph a hard-to-see area, or use a consistent mirror view to track size and surface changes. Do not squeeze, lance, or repeatedly rub the lump. Reduce pressure from tight straps or rough clothing if they irritate it. A clinician may assess mobility, depth, skin changes, and tenderness, then decide whether observation, imaging, sampling, or removal is appropriate. A [Steroid Injection Into The Skin](/treatments/injectables/intralesional-steroid-injection/) may be discussed for particular inflammatory lesions after diagnosis.

Arrange a review if the lump is growing, hard, fixed, repeatedly inflamed, painful, or present without explanation. Seek prompt care for fever, spreading redness, pus, severe tenderness, or a wound that does not heal. Bleeding, crusting, a persistent ulcer, or a new colour change also deserves examination, particularly when the area is exposed to sunlight.

Does the lump feel superficial or deep? Is its mobility reassuring, or do I need imaging? Could friction or an old injury be contributing? If it is removed, will it be examined to confirm the diagnosis?