Patterns in Melanocytic Nevi

Reticular pattern (Figure 9.1A) (most common)

Pigment network characterized by a grid of thin brown lines with hypopigmented ‘holes’ (honeycomb-like pattern)

Benign acquired melanocytic nevi, lentigo simplex, solar lentigo, sometimes seen in melanoma

Globular pattern (Figure 9.1B)

Variously sized brown to gray-black round to oval structures

Acquired melanocytic nevi, congenital nevi

Cobblestone pattern

Similar to globular but closely aggregated angulated globules

Papillomatous dermal nevi, congenital nevi

Homogenous pattern (Figure 9.1D)

Diffuse, uniform and structureless areas ranging from brown, gray-blue to gray black (no pigment network)

Blue nevus (hallmark), ± intradermal nevus, can be seen in metastatic melanoma

Starburst pattern

Pigmented streaks in radial arrangement surrounding entire periphery of lesion

Spitz nevus

Patterns in Acral-Specific Nevi

Parallel furrow pattern (Figure 9.1C)

Found exclusively in glabrous skin (palm/sole), parallel pigmented lines within sulci or furrows of glabrous skin and whitish dots (acrosyringia) between sulci (within ridges)

Acral benign melanocytic nevi

Of note, acral melanoma with parallel ridge pattern

Lattice-like pattern

Rectangular network of brown lines and several whitish dots

Acral benign melanocytic nevi

Fibrillar pattern

Several short and thin brown lines with parallel arrangement but also run oblique to the ridges/furrows of glabrous skin

Acral benign melanocytic nevi

Patterns in Dermatofibromas

Central white area (Figure 9.2A)

Well-circumscribed milky white area in center of firm papule

Reticular network (Figure 9.2A)

Often delicate, pale network seen at periphery

Patterns in Seborrheic Keratosis

Moth-eaten border

Punched out concave areas at periphery of lesion; also seen in ephelis, lentigo and lentigo maligna

Fissures and crypts

Irregular filled craters (crypts), irregular linear keratin filled depressions

Comedo-like openings (Figure 9.2B)

Brownish-yellow or brown-black structures with varying sizes; represents keratin plugs within dilated follicular openings (rarely can be seen in papillomatous dermal nevi)

Milia-like cysts (Figure 9.2B)

White or yellowish discrete round structures of varying sizes; represents intraepidermal horn pseudocysts (can also be seen in papillomatous dermal nevi, rarely in melanoma)

Fingerprint-like structure

Light brown curvilinear lines resembling fingerprints; found in early seborrheic keratosis and solar lentigo

Pattern in Vascular Lesions (hemangioma, angiokeratoma)

Red-blue lacuna (Figure 9.2C, D)

Sharply demarcated oval to round structures with varying shades (red, dark red, red blue to black); represents dilated vascular spaces in upper dermis (if dark red to black may be partially thrombosed)