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Updated: Feb 15, 2026

Development of Compendium for Esophageal Squamous Cell Carcinoma
Published on: April 12, 2024
Primary Cutaneous Spindle Cell Squamous Carcinoma Expressing Smooth Muscle Actin: Diagnostic Pitfalls
Abdullahi Ahmad1,2, Hye Jin Chung1, Jag Bhawan1
1Dermatopathology Section, Department of Dermatology, Boston University School of Medicine, Boston, MA.
Abstract:
Alpha smooth muscle actin (SMA) belongs to the actin proteins. It is a known immunohistochemical marker for tumors of mesenchymal origin. There have been reports of expression of SMA in certain epithelial malignancies in the head and neck and genital regions. In this study, the authors report a primary cutaneous spindle cell squamous carcinoma expressing SMA. Both high- and low-molecular-weight keratins and p63 were positive, and S100 protein, SOX10, MART-1/Melan-A, and muscle-specific actin stains were negative. This case highlights that an epithelial tumor could express a mesenchymal marker, thereby making the diagnosis problematic.
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