Everyone has his/her hobby horses and I am no exception. My [i]bête noire[/i] is use of the term atypical in melanocytic pathology. The best place to start is by defining typical:
[indent=1]1. representative[b]:[/b] having all or most of the characteristics shared by others of the same kind and therefore suitable as an example of it[/indent]
[indent=1]2. characteristic[b]:[/b] characteristic of an individual person or thing[/indent]
In the context of melanocytic nevi, the common or banal nevus (junctional, compound or dermal) is regarded as typical and therefore any nevus that departs from this nevus could in theory be regarded as atypical e.g. balloon cell nevus, signet-ring cell nevus, pseudoglandular nevus etc. Obviously no one in his/her right mind would use the term in this context. However there are numerous occasions where because of histologically worrying features, the lesion is described as atypical e.g. atypical genital nevus, atypical acral nevus, atypical nevus of the scalp, atypical Spitz nevus etc. We now know or think we know that most of these are biologically benign (atypical genital nevus, atypical acral nevus, and atypical nevus of the scalp) and include them in the category of “nevi at special sites”. Provided the dermatologist knows what the pathologist means by “nevi at special sites” and recognizes that they are thought to be of no clinical consequence then all is well!
The real problem arises with the use of the term atypical Spitz nevus. This represents a Spitz nevus which departs by greater or lesser degree from the prototypic lesion. The term has evolved over the years gaining great popularity amongst many dermatopathologists and pathologists. The reasons for this are multiple:
· Numerous papers on the subject by experts in the field of melanocytic pathology
· The increasing proportion of Spitz nevi partially sampled by shave or punch biopsy by the dermatologists
· The problem is that some of the features which would enable a confident diagnosis of benign or malignant are present in the deeper (un-sampled) portion of the lesion e.g. infiltrative versus expansile (pushing) lower border, lack of maturation, deep mitoses or atypical mitoses
· Litigation
The result of this has been a loss of confidence amongst many dermatopathologists or pathologists reporting such lesions. In addition, the diagnostic criteria are the same for both atypical Spitz nevus and spitzoid melanoma. It is all a matter of degree. To my mind (along with the late Bernie Ackerman) what this really means is that when a person makes the diagnosis of atypical Spitz nevus he/she is not really sure whether the lesion is truly benign or malignant. To put it another way, lesions that are categorized as atypical Spitz nevus comprise both Spitz nevi and spitzoid melanomas. While I do not for one moment think that I can confidently differentiate between the two in every case (far from it), I do believe that the creation of this category has resulted in an increase in the diagnosis of this “variant” to the cost of making a confident diagnosis of either Spitz nevus or spitzoid melanoma. It is just too convenient and is an easy way to opt out of making a diagnosis. Certainly over the years I have encountered many examples in consultation where the referring pathologist has wondered whether the lesion is atypical because for example it contains 2 superficial mitotic figures or something similar. I believe that the term should be used very sparingly if at all. It demonstrates diagnostic uncertainty and if used too often, will likely result in loss of confidence in the dermatopathologist by the clinicians. In addition, the clinician may be at a loss as to what to tell the patient and what further treatment to offer if any. It is essential to show all such lesions to colleagues for their help or if necessary send the case to an expert for a consultation.
The issue has been further complicated by the use of sentinel lymph node biopsy in the treatment of “atypical Spitz nevus”. There are well over 100 examples in the literature when I last counted, of “atypical Spitz nevi” with positive sentinel lymph node biopsies and yet the diagnosis has not been changed to Spitzoid melanoma. One cannot but wonder what the point actually was of doing the sentinel lymph node biopsy. In fairness, with the follow-up available (often limited) such sentinel node positive lesions appear not to have progressed and perhaps some would regard them as a “benign” metastasis. Mind you there is one series in the literature where an “atypical Spitz nevus” with systemic spread was included in the study, which is beyond belief. How on earth can a Spitz nevus with systemic spread be anything other than a melanoma?
I realize that I am an anachronism in this field but would love to hear other people’s views to see if I truly am a voice in the wilderness or whether there are others who share my concern.