"Fat fingers:" a clue in the dermoscopic diagnosis of seborrheic keratoses.

"Fat fingers" are thick digitate linear, curvilinear, branched, or oval/circular dermoscopic structures typically seen in seborrheic keratoses where they represent the gyri of their cerebriform surfaces. Their recognition is very useful in the diagnosis of these lesions, especially when the classic features (eg, milia, comedo-like openings) are absent. Histologically and by confocal microscopy the "fat finger" gyri are accentuated by pigmented keratin filling the sulci. "Fat fingers" must be differentiated from other linear structures such as "network-like structures"; branched streaks; network; globules; pigmented ovoid-nests; and streaks/pseudopods seen in different melanocytic and non-melanocytic lesions.