In Situ Lesion

**Semantic type:** Finding

**Definition:** A morphologic finding that usually refers either to intraepithelial dysplastic and architectural changes that involve the entire thickness of the epithelium without invasion of the basement membrane (carcinoma in situ) or proliferation of atypical melanocytes in the dermal-epidermal junction without infiltration of the papillary or reticular dermis (lentigo maligna).

**Synonyms:** - In Situ Neoplasm