Provisioning

Not every microscopical interpretation can be certain. While our diagnostic lives are filled with various scenarios, such as the assessment of a conventional basal cell carcinoma or a stereotypical melanocytic nevus, in which our diagnoses can be utterly explicit, we also face ambiguous situations on a daily basis. We are personally responsible for some ambiguity. Because of limitations in our own skill or perception, we may find ourselves unable to provide utterly certain conclusions regarding a given case or regarding a particular aspect of a given case. Some uncertainty stems from limitations in the field. Because of a lack of precise scientific knowledge or because of insufficient data from studies with proper follow-up, we find ourselves unable to interpret a situation with surety. And some ambiguity is foisted upon us. Key information of diagnostic importance is presumed to be of little relevance or is withheld by clinical colleagues, and diagnostic haziness or misclassification ensues.1 The degree of uncertainty associated with various diagnoses can vary greatly. When the degree of ambiguity is minimal, forging ahead with a nearly-certain diagnosis has almost no down side, presuming that the information we have been provided is accurate. We see atypical melanocytes distributed relatively confluently along the junction within a partial biopsy and are told that the clinical lesion was 2.5 cm in breadth, and there is little to be lost in issuing an outright diagnosis of melanoma in situ (if the handwriting on the requisition is poor and it turns out that the clinical lesion was actually 2.5 mm in breadth, the situation can become more complicated). When doubt reins supreme, it becomes obvious a certain diagnosis cannot be issued and thus a semantic tool or crutch must be employed to convey the essence of the situation and provide a differential diagnosis. Such ambiguous diagnoses can be referred to as descriptive or provisional diagnoses, as they provide a description of the general pathological situation and serve as the basis for providing additional detailed information in the form of a differential diagnosis. Much of the time, the use of a provisional diagnosis is absolutely straightforward. When vacuolar alteration is present along the junction in an atrophic epidermis above a lymphocytic infiltrate with admixed reticular dermal mucin, a diagnosis of atrophic interface dermatitis provides the description and a comment indicating that the differential diagnosis is between lupus erythematosus and dermatomyositis can be added. An undifferentiated epithelial malignancy can be provisionally interpreted simply as a carcinoma with an accompanying discussion of a differential diagnosis based upon morphology, presuming that immunoperoxidase stains fail to shed insight into specific differentiation. A partial biopsy that raises a differential diagnosis of Spitz nevus versus melanoma can be provisionally interpreted as a compound proliferation of melanocytes (there are, of course, many other possible wordings in this setting). The range of provisional diagnostic possibilities is nearly limitless and parallels the spectacular diversity of our field. While descriptive terminology constitutes an absolutely necessary component of daily reporting, the act of provisional diagnosis represents a complex, underemphasized, and occasionally perilous activity. Issues and road bumps associated with such provisioning are discussed in brief in the sections that follow. A good provisional diagnosis should be sufficiently broad to be inclusive, sufficiently narrow to be incisive, and sufficiently unique to limit misconstrual. Clearly, a provisional diagnosis of dermatitis would be technical correct and thus potentially utile in the interpretation of any inflammatory skin disease, but its excessive breadth suggests that use should be sparing. A narrower diagnosis of interstitial dermatitis with an accompanying differential between interstitial granuloma annulare and early morphea has far greater clinical value. Tired diagnostic terms, such as atypical melanocytic hyperplasia, that are imprecisely defined yet have potential specific meaning to some clinical colleagues should be eschewed. A provisional diagnosis can be misinterpreted or can be interpreted in a way other than intended. The reinvention of provisional diagnoses by our clinical colleagues can be endlessly fascinating. In our laboratory at the University of California, a case interpreted provisionally as a junctional proliferation of melanocytes with