Subcutaneous pseudomembranous fat necrosis: new observations

Area of Science:

• Dermatopathology
• Histopathology
• Immunohistochemistry

Background:

• Pseudomembranous fat necrosis is a rare condition characterized by pseudocystic cavities lined by membranes.
• The exact mechanism of pseudomembrane formation remains unclear, with necrotic fat cells considered a primary component.

Purpose of the Study:

• To investigate the nature and evolution of pseudomembranous fat necrosis in various panniculitides.
• To elucidate the cellular and molecular mechanisms underlying pseudomembrane formation.

Main Methods:

• Review of 341 panniculitis cases for pseudomembranous fat necrosis.
• Histopathological and immunohistochemical analysis (CD68, lysozyme) of 12 selected cases.
• Correlation of biopsy timing with lesion evolution.

Main Results:

• Pseudomembranous fat necrosis was identified in 30 of 341 panniculitis cases, notably in sclerosing panniculitis and traumatic panniculitis.
• Early pseudomembranes showed vesicular or pyknotic nuclei, while later stages lacked nuclear elements.
• Immunohistochemistry confirmed the presence of histiocytic markers (CD68, lysozyme) in pseudomembranes.

Conclusions:

• Pseudomembranous fat necrosis is a dynamic process influenced by lesion evolution.
• It arises from the interaction between disintegrated fat cell remnants and macrophages.
• CD68 and lysozyme are valuable markers for identifying pseudomembranes in panniculitis.