Patterns in Benign Lesions

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

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

Pigmented streaks in radial arrangement surrounding entire periphery of lesion

Spitz nevus

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}

Rectangular network of brown lines and several whitish dots

Acral benign melanocytic nevi

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

Acral benign melanocytic nevi

Central white area
(Figure 9.2A, B)

Well-circumscribed milky white area in center of firm papule

Reticular network
(Figure 9.2A, B)

Often delicate, pale network seen at periphery

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

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

Comedo-like openings
(Figure 9.2C, D)

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 9.2C, D)

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

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

Red-blue lacuna
(Figure 9.3C, 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)