Common symptoms of breast cancer include:

A new lump or mass in the breast or underarm (armpit) — often painless, hard, and irregular in shape, though some are tender, soft, or round
Swelling of all or part of the breast, even without a distinct lump
Skin dimpling or puckering (sometimes described as looking like an orange peel)
Breast or nipple pain
Nipple retraction (turning inward)
Nipple or breast skin that is red, dry, flaking, or thickened
Nipple discharge other than breast milk, including blood
Swelling of lymph nodes under the arm or near the collarbone

A few important caveats:

Many breast cancers, especially in early stages, cause no symptoms at all — this is why routine screening mammograms matter, since they can detect cancer before a lump is felt.
Most breast lumps are not cancerous (common benign causes include cysts and fibroadenomas), but any new lump or persistent change should be evaluated by a doctor rather than self-diagnosed.
Inflammatory breast cancer (rarer, more aggressive) tends to present differently — with redness, warmth, and swelling that can resemble an infection rather than a lump.

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