These four volumes are devoted to differential diagnosis in dermatopathology, each consisting of 45 sets, 180 sets in all, of apparent histopathologic look-alikes that are contrasted in a manner which establishes criteria for differentiating them. Distinctions between the contrasting pairs of diseases are presented in capsule and table form by emphatic telegraphic statements. Photomicrographs in color that differentiate impressively the histopathologic features of contrasted diseases are presented at scanning, intermediate, and high magnification. Clinical photographs in color permit a reader to visualize the condition in the gross, an advantage that is particularly beneficial to a pathologist. The discussions that follow the tabulated points and counterpoints elaborate first on histopathologic attributes that each pair of contrasted diseases have in common, and then on correlation between their appearance histopathologically and clinically, their usual clinical course, and, last, the histopathologic differential diagnosis. Among the many sets of contrasted diseases are Spitz’s nevus vs. melanoma, desmoplastic trichoepithelioma vs. morpheiform basal-cell carcinoma, Darier’s disease vs. Grover’s disease, pemphigus vulgaris vs. Hailey-Hailey disease, granuloma annulare vs. necrobiosis lipoidica, alopecia of lupus erythematosus vs. alopecia of lichen planus, proliferating tricholemmal cystic acanthoma vs. proliferating tricholemmal cystic carcinoma, and pseudolymphoma vs. malignant lymphoma.