The value of skin biopsy in inflammatory dermatoses.

The skin biopsy is considered one of the most important tools in dermatology. Two primary reasons a clinician may perform a skin biopsy are either to establish a diagnosis or to evaluate therapy. The objective of this study was to critically assess the value of the skin biopsy as a diagnostic test for inflammatory dermatoses. One hundred consecutive skin biopsy specimens where an inflammatory dermatosis was queried were reviewed. To assess the diagnostic ability of the skin biopsy, the frequency with which a correct diagnosis was made based on histopathological analysis alone was recorded, that is, an initial "blind" diagnosis made without clinical data. Once this was recorded, the clinical history was provided and a posthistory diagnosis reached. The posthistory diagnosis was then compared with the final working diagnosis in the patient case notes. In 55% of cases, histology was able to provide a prehistory specific diagnosis. In 31% of cases, histology was not able to provide a specific diagnosis but could provide a differential diagnosis. In two thirds of these (20 of the 31 cases), the diagnosis was reached posthistory with clinicopathologic correlation. In 12% of cases, histology could only provide a pattern analysis, and in 2% of cases, only a descriptive report could be issued. In 13% of cases, the biopsy provided the final working diagnosis, which had not been considered clinically. The skin biopsy for inflammatory dermatoses is clearly a worthwhile investigative procedure. Prehistory blind histology based on microscopic data provided an accurate diagnosis correlating to the working diagnosis in 53% of cases. The diagnostic boundaries of dermatopathology are such that in an additional 25 cases (25%) a diagnosis was reached with aid of clinical data proving the importance of providing a well-thought-out differential diagnosis. Overall, in 78% of cases, histology with the aid of clinical information was able to provide an accurate diagnosis correlating to the working diagnosis.