Basal cell adenoma with S-100 positive stroma: a case report and literature review

Basal cell adenoma (BCA) of the salivary gland with presence of abundant S-100-positive stromal cells has been rarely reported. A case occurring in a 75-year-old man is presented here, as well as a review of the literature on the subject. The patient presented with a nodule in the right parotid gland. In addition to the typical features of BCA, histologically the resected tumor showed a substantial amount of stroma rich in S-100-positive spindle cells, a rarely reported finding in BCA. These cells were unreactive with a panel of myoepithelial markers, including calponin, p63, muscle-specific actin (MSA), smooth muscle actin (SMA), cytokeratin 14 (CK14), and glial fibrillary acidic protein (GFAP). Our results, in accordance with other reports, do not support a myoepithelial nature of these S-100-positive cells, and their precise nature remains elusive.