Histopathology of morphea: Sensitivity of various named signs, a retrospective study

Morphea or localized scleroderma is characterized histopathologically by sclerosis, fibrosis, and atrophy of the skin and subcutaneous tissue. Various authors have named the characteristic findings seen in histopathology of morphea and have labeled them as specific signs, including line sign, cookie-cutter sign, and square biopsy sign. Besides, other findings mentioned include high eccrine glands and the presence of interstitial mucin. The present study was undertaken to assess the sensitivity of these tests in the histopathological diagnosis of morphea.

All cases clinically diagnosed and histopathologically reported as morphea in the last 3 years (September 2016 to August 2019) were included. The slides were reviewed by two independent investigators for the presence of line sign, cookie-cutter sign, square biopsy sign, high eccrine glands, and mucin. The sensitivity of these signs in accurately diagnosing morphea was assessed. Besides, specificity, positive predictive value, and negative predictive value of these signs were assessed using 40 random histopathology slides as controls.

The highest sensitivity was of high eccrine glands (82.5%) followed by the presence of mucin in the dermis (77.5%). Cookie-cutter sign and square biopsy signs were seen in 70% and 62.5% patients, respectively. Line sign was least sensitive of all, seen in 45% of biopsy specimens, but was most specific (82.5%).

A fair number of biopsies of morphea displays the presence of high eccrine glands, mucin, cookie-cutter sign, square biopsy sign, and line sign. These signs thus can be of immense help to the dermatopathology trainees.