Practical problems and pitfalls
Some melanomas that are initially misdiagnosed as naevi come to attention when the tumour recurs. I get to see most of such cases from my country, the Netherlands, usually with the request to provide a second opinion, and this allows me to make some observations, at least regarding the dutch situation - with is probably not that much different from that of many other countries. In my experience, simple, avoidable shortcomings in the biopsy procedure, the evaluation of the biopsy and exchange of information are common causes, or contributory causes, of melanoma underdiagnosis. A high-quality routine probably contributes more to the avoidance of melanoma underdiagnosis than does an intricate knowledge of rare melanocytic variants. Part of that high-quality routine is an appropriate sense of the limitations of one's own diagnosic experience in this field, and easy accesss to a colleague with special expertise in this area.
In order to minimize the chance of melanoma underdiagnosis (complete elimination of underdiagnosis is probably impossible), it is very important that the lesion is completely excised, so that the pathologist is able to study the lesional architecture in its entirety. This is very different from, say, a basal cell carcinoma, which can confidently be diagnosed or excluded on the basis of a punch biopsy or superficial shave biopsy. The clinician may not have considered the possibility that the lesion might be melanocytic; that situation canot be avoided. However, if the lesion is removed for diagnostic purposes and is considered to be melanocytic, or possibly melanocytic, an excisional biopsy provides the optimal specimen and therefore the best opprtunity for the pathologist to establish the correct diagnosis. In cases sent to me in consultation, I tend to be very catious about making an unequivocal diagnosis when confronted with an incisional or otherwise suboptimal biopsy specimen.
Biopsy trauma is a second cause of many problems. Squeezing the specimen with a biopsy forceps is a common cause of tissue damage, with potentially dire consequences. In case of biopsy trauma, the pathologist is well advised to add a statement to that effect, and must feel free to provide a qualified rather than a completely certain diagnosis. Discussing the poroblem with the clinician is, of course the way to go, in order to avoid similarly suboptimal biopsy specimens in the future (and in order to foster a good working relationship with the clinician).
Clinical information should be precise, complete, and clear. If the lesion is removed for diagnostic purposes, there reason for that, and this reason should be specified at all times. A remark that the lesion was 'suspicious' or 'atypical' is noninformative. If the clinician indicates that the lesion is removed because after a period of stability, it has started to become more papular and has developed perilesional erythema, a diagnosis of early halo naevus would explain those features. Asymmetrical pigmentation might be accounted for by a combined navus with eccentric blue naevus component. An irregular contour and colour variegation might be related to previous superficial shave excision, which should at all times be mentioned in the cinical information. If doable (and this is so much easier than it was a number of years ago!), a digitial photograph of the lesion, or even of the dermatoscopic appearance, should accompany the pathology request. Under such optimized circumstances, the pathologist has the best chance to correlate the clinically suspicious findings with the histological apparance of the lesion.