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ABCD rule of dermatoscopy: A semiquantitative algorithm that evaluates symmetry or asymmetry (A), sharp border demarcation (B), multiple colors (C), and structural components in a lesion (D). The criteria in each group are given a point and then multiplied by cofactors to determine the total dermatoscopy score (TDS). A score × 1.3 + B score × 0.1 + C score × 0.5 + D score × 0.5 = TDS. TDS greater than 5.45 is highly suggestive of a melanoma.

Acrosyringia: Monomorphous, round, white structures found only in the ridges on the palms and soles. They represent the intraepidermal eccrine ducts and are said to look like a string of pearls.

Anisotrichosis: The presence of hairs with variable thickness as seen in androgenic alopecia.

Annular-granular structures: Brown or gray fine dots that surround follicular openings. These are seen only on the face, nose, and ears (site specific) and represent melanophages and/or atypical melanocytes.

Arborizing vessels: Thick and/or thin in-focus red tree-like branching telangiectatic blood vessels.

Asymmetry within a lesion: Using the mirror image technique a lesion is bisected by two lines that are placed 90 degrees to each other. There is asymmetry of color and/or structure if the color and/or structure on the left side are different from the right side and lower half is different from the upper half.

Basal cell carcinoma, criteria: Absence of pigment network, arborizing blood vessels, pigmentation, ulceration, spoke-wheel structures.

Black dots, hair: Black dots are inside the follicular openings and represent broken hair shafts.

Black dots, skin: Round structures smaller than globules that represent melanin and/or atypical melanocytes that are in the epidermis.

Black lamella: A superficial, thin black shiny area seen in flat benign nevi that represents pigmented parakeratosis. Tape stripping can remove the black lamella and hidden local criteria such as pigment network may or may not then become visible.

Blanch test: Diffuse erythema seen in a lesion blanches away with direct pressure using dermoscopic instrumentation. What remains are the nonerythematous features of a lesion.

Blood pebbles: One component of a subungual hematoma characterized by irregular purple dots and/or globules that represents blood.

Blotch, irregular: Irregular in shape, asymmetrically located, structureless (ie, absence of network, dots, or globules) shades of black, brown, or gray color that are bigger than dots and globules.

Blotch, regular: Uniform, symmetrically located, structureless (ie, absence of network, dots, or globules) shades of black, brown, or gray color that are bigger than dots and globules.

Blue ovoid nests: One of the shapes of pigmentation seen in basal cell carcinoma.

Blue-white veil: Irregular, structureless area of confluent blue color that does not fill the entire lesion with an overlying whitish ground glass appearance.

Central white patch: Centrally located, homogeneous, ...

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