When blood vessels appear as dots, their color is red however, when the underlying structure is melanin, their color ranges from black, brown, to blue-gray depending on the depth and concentration of the melanin in the skin (Tyndall effect).īlack dots are often due to melanin pigment accumulation in the stratum corneum, but can also be due to vertical stacking of pigment within the epidermis or due to heavy aggregates of melanin in small clusters of melanocytes or keratinocytes located in the upper layers of the epidermis (just below the stratum corneum). ĭots are small, round structures of less than 0.1 mm in diameter (similar to the diameter of a terminal hair follicle) that correlate with blood vessels or melanin pigment. Dermoscopic differential diagnosis is broad and includes blue nevi, combined nevi, areas of extensive regression, pigmented nodular melanoma, primary or metastatic melanoma, BCC and radiation tattoos. Histologically, it corresponds to densely pigmented melanocytes or melanophages in the dermis. Homogenous blue pattern (structureless blue) is characterized by the presence of blue color with the absence of other dermoscopic structures throughout the entire lesion. The pigment network in melanocytic lesions is further characterized as typical or atypical. A wide diameter of dermal papillae would correspond dermoscopically to wider network “holes,” whereas narrow dermal papillae would result in a denser sieve of the grid. The less-pigmented “holes” of the network correspond to tips of the dermal papillae and the overlying suprapapillary plates of the epidermis. The anatomic basis of the pigment network is melanin in keratinocytes or in melanocytes along the DEJ, representing the way the rete ridge pattern of the epidermis appears when viewed in the horizontal plane. The pigment network consists of a grid of intersecting pigmented “lines” forming a honeycomb pattern.

Some colors, especially when associated with selected dermoscopic structures, also have important histopathologic correlates, such as white globules (associated with balloon-cell changes), homogeneous yellow to orange areas (associated with cell xanthomization) or black lacunae (associated with blood thrombosis). Other important determinants of lesion color include hemoglobin in red blood cells (pink to red colors), lipids or keratin (yellow) and collagen fibers in the dermis (white color). 3.20 Multiple Blue-Gray Non-aggregated Dots and Globules.3.14 Fissures and Ridges (“Brain-like' or 'Cerebriform Appearance”).3.2.4 Irregular hyperpigmented structureless area (Blotch).3.2.3 Regular hyperpigmented structureless area (Blotch).3.2.2 Hyperpigmented structureless areas (Blotches).3.2.1 Hypopigmented structureless areas.1 Differences between dermoscopic and histopathologic criteria.

Histopathologic definition