Blink versus Systematic examination in Dermoscopy

Melanoma mimicking seborrheic keratosis: an error of perception precluding correct dermoscopic diagnosis.Braga JC, Scope A, Klaz I, Mecca P, Spencer P, Marghoob AA.
Department of Dermatology, Memorial Sloan-Kettering Cancer Center, New York, New York 10022, USA.

Seborrheic keratosis is a common skin lesion that can usually be recognized either clinically or dermoscopically. However, melanomas mimicking seborrheic keratoses, as well as melanomas arising in association with seborrheic keratoses, have been described. We report the case of a patient with a lesion that initially revealed "classic" dermoscopic features of a seborrheic keratosis. However, during follow-up, changes in color developed within the center of the lesion that led the clinician to the correct diagnosis of melanoma. Upon retrospective evaluation of the baseline image of the lesion; the clinician was now able to "see" that which his brain could not appreciate on initial examination and to realize that the lesion had subtle features suspect for melanoma. This case represents a diagnostic pitfall due to errors in perception. Dermatologists should be cognizant of "errors in perception"; we suggest that a final dermoscopic judgment of a seborrheic keratosis be rendered by combining the gestalt diagnosis of the overall pattern, with deliberate dermoscopic analysis of all quadrants of the lesion.

PMID: 18328596 [PubMed - indexed for MEDLINE]
From Club Dermaweb
A dermatologist’s brain will always favour the overall impression of the right side of the brain over the detailed analysis of the left side of the brain, both with a dermoscope as well as with the naked eye. The first is intuitive, fast and often very beneficial and efficient. Detailed rational analysis, which involves looking at the tumour section by section and studying all the basic signs and dermoscopic patterns, is tedious and slow. It is therefore logical that the dermatologist’s first impression tends to influence the way he/she interprets the detailed analysis, or even convince them not to do it. In this example a pigmented lesion of the neck found during a routine examination was quickly identified as seborrheic keratosis because he/she found numerous pseudo-horny cysts. When the patient was seen a year later, the lesion was a lot darker and had a blue-white veil. Excision was performed and an SSM associated with seborrheic keratotic-like epidermal hyperplasia was found, even though it wasn’t possible to distinguish between a verrucous melanoma and a composite lesion. The dermatologist looked at the initial dermoscopic image again and noticed that some aspects which suggested MM were already present a year earlier in a limited area at the periphery of the lesion. Papillomatous epidermal hyperplasia with pseudo-horny cysts has already been found in a small number of cases of malignant melanomas and does not allow this diagnosis to be officially ruled out. The error in perception which makes dermatologists favour the overall picture in relation to detailed analysis should be kept in mind to avoid mistakes like this.