Immunohistochemistry in Dermatopathology: A Retrospective Study of the Most Frequently Used Antibodies.

Immunohistochemistry (IHC) is an ancillary technique to improve diagnostic accuracy and prognosis in histopathology of both inflammatory and neoplastic cutaneous disorders. However, only a few studies address specifically the set of antibodies available for inflammatory or neoplastic skin diseases. In this study, we analyzed the IHC studies performed for inflammatory and neoplastic skin disorders in cutaneous biopsies taken in our department during 1 year. From a total of 8579 skin biopsies performed throughout the year 2011 in our department, IHC studies were performed in 283 cutaneous biopsies. The total number of different antibodies used in the IHC studies of those 283 skin biopsies was 129. These antibodies were used in 1421 studies, with a mean of 5 cases per antibody studied. The proliferative marker MIB-1 was the single antibody with the highest number of studies, with a total of 119 (8.3% of all IHC studies performed), followed by 113 of CD3 (7.9% of total IHC studies) and 108 of Melan-A (7.6% of total IHC studies). Other hematopoietic differentiation markers, such as CD20, CD4, and CD8, and other melanocytic markers, such as S-100 protein, Melan-A, and HMB-45, were all investigated with a frequency greater than 50 studies each. The 2 most frequent categories were melanocytic neoplasms, which represented 25% of all specimens studied by IHC, and the proliferations of lymphohematopoietic nature, which were 20% of all studied samples and represented by far the highest number of IHC stains per case to reach a final diagnosis. Both previous categories together accounted for 45% of all diagnoses in which IHC was performed. We compare our results with the only similar study previously published in the literature. The gold standard panel of antibodies that should be available in everyday practice in dermatopathology to arrive at a specific diagnosis in each cutaneous inflammatory disease or neoplastic process involving the skin is still a matter of discussion.