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S100A6 expression in cutaneous smooth muscle neoplasms
Munir H Idriss1, Dirk M Elston2
1Ackerman Academy of Dermatopathology, New York, NY, USA.
Summary
S100A6 immunohistochemistry can aid in diagnosing skin lesions. Weak S100A6 staining suggests leiomyoma (LM), while strong staining indicates leiomyosarcoma (LMS), improving differential diagnosis.
Area of Science:
- Oncology
- Dermatopathology
- Protein Expression Analysis
Background:
- S100A6 protein is found in various tissues.
- Distinct S100A6 immunohistochemistry patterns can aid in diagnosing challenging lesions.
- Leiomyomas (LM, ALM) and leiomyosarcomas (LMS) are distinct smooth muscle tumors.
Purpose of the Study:
- To evaluate the S100A6 antibody staining pattern in pilar leiomyoma (LM), angioleiomyoma (ALM), and cutaneous leiomyosarcoma (LMS).
- To determine the utility of S100A6 expression in differentiating these smooth muscle tumors.
Main Methods:
- Immunohistochemistry was performed using an S100A6 antibody on 22 cases each of LM, ALM, and LMS.
- Staining intensity (weak, moderate, strong) and localization (nucleus, cytoplasm) were assessed.
- Statistical analysis (Mann-Whitney U test) compared staining patterns between tumor types.
Main Results:
- S100A6 stained both nucleus and cytoplasm in positive myocytes.
- Positive S100A6 staining was observed in 64% of LM and 86% of ALM, predominantly weak.
- 95% of LMS showed moderate to strong S100A6 staining.
- Significant differences in staining intensity were found between LM vs LMS (p=0.025) and ALM vs LMS.
Conclusions:
- S100A6 immunohistochemistry is a valuable tool for differentiating cutaneous smooth muscle tumors.
- Weak or absent S100A6 staining supports a diagnosis of leiomyoma (LM/ALM).
- Moderate to strong S100A6 staining is indicative of cutaneous leiomyosarcoma (LMS).
