Atypical Mixed Tumor of the Skin in the Gluteal Region with Strong and Diffuse Nuclear Expression of the p16 Stain: A Case Report.

Benign, atypical, or malignant chondroid syringoma (mixed tumor of the skin) have almost identical clinical presentation with similar histological features, except for infiltrative growth, and perineural and vascular invasion in the malignant type. Tumors with borderline features are described as atypical chondroid syringoma. Immunohistochemical profiles in all three types are similar, with the the main difference in the expression of the p16 stain. We present a case of an atypical chondroid syringoma in an 88-year-old female patient with a subcutaneous, painless nodule in the gluteal region and with diffuse, strong nuclear immunohistochemical staining for p16. To our knowledge, this is the first such reported case.