Misclassification of melanocytic lesions

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Misclassification of melanocytic lesions[edit]

When melanocytic lesions do not display clear-cut melanocytic features, or on the contrary show features associated with non melanocytic lesions, the diagnostic process could result in their misclassification as non-melanocytic.

Melanomas mimicking Basal cell carcinomas[edit]

When a melanoma expresses a pink background, crystalline structures and/or arborizing vessels, it could be misdiagnosed as a basal cell carcinoma. Of the features noted above only arborizing vessels are considered specific for basal cell carcinomas, having a PPD of 94%. However, this feature has been described infrequently in melanomas, challenging the dermoscopic distinction of the two entities and having the final diagnosis made by the pathologist.

Melanomas mimicking benign non-melanocytic lesions[edit]

Melanomas occasionally display features seborrheic keratoses such as milia-like cysts and comedo-like openings. One should remember not to rule out a melanocytic lesion by noticing non-melanocytic structures. Adhering to the algorithms’ first step by deciding whether a lesion is melanocytic based on the presence or absence of a network, globules, streaks or a homogenous blue pattern, would help avoiding this misclassification.

Melanomas mimicking dermatofibromas[edit]

The gestalt pattern of melanomas and dermatofibromas can be similar, thus to achieve high diagnostic accuracy it is imperative to notice specific structure which support the global pattern. As stated above, contrary to dermatofibromas, melanomas generally do not show vessels and crystalline structures within the scar-like areas and lack a dimple sign. However, whenever an atypical dermatofibroma is suspected a reasonable management strategy would be to biopsy the lesion.

melanomas mimicking lichen planus-like keratosis[edit]

Both melanomas and LPLK’S can feature pigmentation and extensive regression structure making their distinction occasionally challenging. A clue to lplk’s diagnosis is a seborrheic keratosis or solar lentigo at the periphery of the lesion and rather coarse blue gray granules in contrast to the fine granularity associated with melanoma. In addition, both lesions can at times exhibit a pink structureless pattern with remnants of a pigment network, and the definite diagnosis is rendered though histologic examination.

Melanomas mimicking pyogenic granulomas[edit]

Both amelanotic melanomas and pyogenic granulomas can present as red evolving nodules, occasionally ulcerated or eroded. Pyogenic granulomas can exhibit vascular structures, further adding to the confusion .Considering the dismal consequences of missing a nodular melanoma, it is strongly suggested that all pyogenic granulomas would be removed and sent to histologic examination.

Discussion[edit]

As the human decision making is an intricate process, its’ reduction into a stepwise linear process can result in oversimplification leading to the incorrect diagnosis. Confusing a melanoma with a malignant non-melanocytic lesion (ie BCC or pigmented Bowen’s disease) would frequently result in similar management. However, confusing a malignant lesion with a benign lesion could have dismal consequences. It is essential to integrate history and clinical features with the algorithmic process and diagnostic clues in order to reduce diagnostic errors.

Table 1- Features and mimickers[edit]