Differentiating Early Stage Cystic Keratoacanthoma, Nodular Basal Cell Carcinoma, and Excoriated Acne Vulgaris by Clinical Exam, Dermoscopy, and Optical Coherence Tomography: A Report of 3 Cases.

Making accurate diagnoses when certain lesions are in a relatively young stage can prove challenging, as their "textbook descriptions" are often not fully apparent, and may in fact be markedly different. The authors present three interesting cases of early lesions that were clinically difficult to differentiate from one another: a cystic variation of a keratoacanthoma squamous cell carcinoma, a basal cell carcinoma, and an excoriated facial acne vulgaris. The subtle clinical nuances found in each of these cases demonstrated the importance of a careful clinical evaluation; however, this was not sufficient for adequate assessment of whether or not to biopsy. With early lesions such as these, the use of the noninvasive imaging modalities of dermoscopy and optical coherence tomography becomes critical in order to avoid unnecessary biopsy. The discussion of the clinically and dermoscopically challenging features is both instructive and enlightening. Oftentimes, "textbook descriptions" of lesions focus on the description of an already mature stage of growth, despite the fact that we continue to strive toward earlier detection of potential malignancies. With this in mind, the features found with optical coherence tomography proved essential to the elucidation of these difficult lesions. These three interesting cases illustrated the challenges encountered when dealing with early lesions specifically. The authors bring to light features in each of these cases that are often not thought of as being the "typical" presentation in each lesion category and demonstrate the clinical utility of noninvasive devices in difficult-to-diagnose cases such as these.