Histopathologic spectrum of morphea: a single-center retrospective study

Background. Morphea is a rare autoimmune disease that often affects the skin and subcutaneous tissue. Objective. The aim of our study is to reveal the relationship between demographic characteristics of the patients, location of the lesions, clinical subtype of morphea and histopathological findings. Methods. We studied 78 patients diagnosed with morphea between 2016 and 2022 at the Department of Pathology, Prof. Dr. Cemil Taşcıoğlu City Hospital. 72 patients were included in the study. Hematoxylin and Eosin stain slides of cases were retrieved from the pathology archive and were evaluated by two pathologists under blinded conditions. Flattening of rete ridges, location of inflammatory infiltrate, grade of inflammatory infiltrate, presence of plasma cells, presence of eosinophils, homogenization of dermal collagen, decrease of skin appendages, basal pigmentation and melanin incontinence were evaluated. Statistical analyses were performed using SPSSv.20. Results. The most common clinical presentation was plaque type(87.5%) and histopathological findings were homogenization of dermal collagen(100%) and decrease of skin appendages (98.7%). Flattening of the rete ridges was observed in 46.2% of the patients. Severity of the inflammatory infiltrate was found to be higher in these patients(p=0.028). Basal pigmentation was observed in 59% of the patients. Line sign was more common in lower extremity lesions among all localizations (p=0.015). Conclusions. The histopathologic features of morphea are variable and confusing. Particularly, in cases with collagen homogenization, morphea should be considered in differential diagnosis with clinical correlation. In addition, the ‘line’ sign could be helpful for identifying lesions located in the lower extremities.