The limitations of dermoscopy: false positive and false negative tumors

Abstract

Dermoscopy has been documented to increase the diagnostic accuracy of clinicians evaluating skin tumors, improving their ability to detect skin cancer and better recognize benign moles. However, dermoscopically "false positive" and "false negative" tumors do exist. False positive diagnosis usually leads to unnecessary excisions. False negative diagnosis is much more dangerous, since it might result in overlooking a cancer, with severe undesirable consequences for the patient and the physician. Therefore, management strategies should mainly focus on addressing the risk of dermoscopically false negative tumors.

The most frequent benign tumors that might acquire dermatoscopic characteristics suggestive of malignancy are seborrheic keratosis (SK), including solar lentigo, melanoacathoma, irritated, clonal and regressive SK, angioma (mainly thrombosed angioma and angiokeratoma), dermatofibroma, benign adnexal tumors and nevi (Clark, Spitz, recurrent, combined, sclerosing). The most useful clues to recognize these tumors are the following: solar lentigo-broad network; melanoacanthoma-sharp border; irritated SK-regularly distributed white perivascular halos; clonal SK-classic SK criteria; regressive SK-remnants of SK; targetoid hemosiderotic angioma-dark center and reddish periphery; thrombosed angioma-sharp demarcation; angiokeratoma-dark lacunae; atypical dermatofibromas-palpation; follicular tumors-white color; sebaceous tumors-yellow color; Clark nevi-clinical context; Spitz/Reed nevi-age; combined nevi-blue central area; recurrent nevi-pigmentation within the scar; sclerosing nevi-age and location on the upper back; blue nevi-history

Malignant tumors that might mimic benign ones and escape detection are melanoma (in-situ, nevoid, spitzoid, verroucous, regressive, amelanotic), squamous cell carcinoma (mainly well-differentiated variants) and rarely basal cell carcinoma (non-pigmented variants). The most useful clues to recognize the peculiar melanoma subtypes are: melanoma in situ-irregular hyperpigmented areas; nevoid melanoma-history of growth; spitzoid melanoma-age; verrucous melanoma: blue-black sign; regressive melanoma-peppering or scar-like depigmentation; amelanotic melanoma-pink color, linear irregular vessels, dotted vessels.

In this paper we summarized the most frequent dermoscopic variations of common skin tumors that are often misinterpreted, aiming to assist clinicians to reduce the number of false diagnoses.

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