Table 1: Primary lesions.
| Primary lesions | Definition | Examples |
| Macule | Flat (nonpalpable) circumscribed skin discoloration | Café au lait, vitiligo, freckle, junctional nevi, tinea versicolor, melasma |
| Patch | Large macule, > 1 cm | Vitiligo, nevus flammeus |
| Papule | Solid elevation, < 0.5 cm in diameter | Acrochordon (skin tag), acne, nevus, melanoma, molluscum contagiusum |
| Plaques | Broad papule or confluence of papules, > 0.5 cm, no deep component | Psoriasis, eczema, tinea corporis, mycosis fungoides |
| Nodules | Solid elevation, > 0.5 cm in diameter, larger deeper papule | Rheumatoid nodule, xanthoma, lipoma, metastatic carcinoma, erythema nodosum |
| Tumors | Large nodule | Lipomas, melanoma |
| Wheals | Evanescent, pruritic edematous, plaque (a hive) | Urticaria, dermographism, urticaria pigmentosum |
| Vesicle | Papule that contains clear fluid (a blister), epidermal, may be unilocular or multilocular | Herpes simplex, herpes zoster, contact dermatitis |
| Bulla | Large vesicle, > 0.5 cm in diameter | Pemphigus vulgaris, bullous pemphigoid, bullous impetigo |
| Pustule | Papule that contains purulent fluid | Acne, folliculitis, pustular psoriasis, impetigo |
| Cyst | Nodule that contains fluid | Acne, epidermal inclusion cyst, pilar cyst |