Validation of Digital Pathology for Primary Histopathological Diagnosis of Routine, Inflammatory Dermatopathology Cases

Background: Digital pathology (DP) systems have been validated for routine, histopathological diagnosis by several investigators. The diagnostic matter in previous studies is composed mostly of neoplasms. However, in dermatopathology, inflammatory diseases constitute a greater proportion of cases and have been underrepresented in this literature. Herein, we report the results of a prospective, DP side-by-side validation study comparing the histologic assessment of routine, clinical inflammatory dermatopathology cases by whole slide imaging (WSI) and traditional light microscopy (LM). Methods: Glass slides were digitized at x40 magnification. Two dermatopathologists rendered diagnoses digitally and immediately thereafter by light microscopy. Additional recuts, special, and immunohistochemical stains obtained during workup were scanned and evaluated similarly. Morphological features used to make diagnoses and appreciable differences in histology were recorded. Results: A total of 332 slides representing 93 cases were examined, including 157 hematoxylin & eosin sections, 132 special stains, and 43 immunohistochemical slides. In total, 333 microscopic features important for rendering inflammatory diagnoses were identified. Two discrepant instances were noted wherein Gram-positive cocci were identified using traditional microscopy but not by DP (x40 scan). Eosinophils, melanin granules, and mucin were identified on both modalities but were noted to have different appearances. Conclusions: Our findings indicate that DP is sufficient for primary diagnosis in inflammatory dermatopathology. Higher magnification scanning may be required to identify submicron features, such as microorganisms. Subtle differences in image quality between these 2 modalities may contribute to varied histologic interpretations of which pathologists should be aware when validating clinical DP systems.