Morphea is an autoimmune skin disease with protean clinical manifestations. Histologic features are similarly variable, and skin biopsies may be nondiagnostic. A single-institution retrospective cohort study was conducted. Morphea patients who had a biopsy in 2005-2015 were included, and a histopathological review was conducted by 2 pathologists. There were 51 biopsy specimens from 40 subjects. The most common histologic features were dermal sclerosis (90%), dermal thickening (78%), collagen homogenization (86%), a superficial and deep infiltrate (76%), a moderate-abundant inflammatory infiltrate (73%), and periadnexal fat loss/decreased skin appendages (71%). Twenty-four specimens were not diagnostic of morphea. In these specimens, the main clues to diagnosis included the presence of dermal sclerosis (79%), subtle collagen homogenization (75%), dermal thickening (58%), moderate-to-abundant plasma cells (50%), and perineural inflammation (50%). There were no statistically significant differences between active and inactive lesions, nor untreated and treated lesions. The histopathologic features of morphea are variable and a high proportion of biopsies are not diagnostic. Clinicians and pathologists should have a high degree of suspicion to correctly make the diagnosis of morphea.
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