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

A symptomatic intercalated duct lesion of the parotid gland: a case report with immunohistochemical and genetic analyses

Intercalated duct lesions (IDLs) are usually asymptomatic. We report a case of IDL, in which a palpable mass formed. The patient was a 45-year-old Japanese male, who noticed a mass in the left parotid region. The nodular lesion was well-circumscribed, but did not have a fibrous capsule or exhibit infiltrative growth. It contained a small cystic space and consisted of basaloid cells arranged in a cribriform pattern and inner ductal cells. It had some solid areas of nest-like proliferation displaying mild cellular atypia. Immunohistochemically, the luminal cells were positive for cytokeratin (CK)7 and epithelial membrane antigen, and the abluminal cells were positive for CK5/6, p63, and DOG1. S-100 protein-positive stromal cells were also seen. The lesion's cells were all positive for SOX10, and the nuclei of some basaloid cells were positive for β-catenin. The Ki-67 labeling index was 3.8%. The ductal cells contained diastase-digestion-resistant, Periodic acid Schiff-positive zymogen granules. Genetically, the lesion harbored a missense mutation in the CTNNB1 gene. We diagnosed the lesion as an IDL. As IDLs are usually small non-neoplastic lesions, symptomatic cases are rare. Based on its common immunohistochemical and genetic features, IDL may be a precursor of basal cell adenoma/adenocarcinoma, such as intercalated duct adenoma.

Basal Cell Adenoma and Basal Cell Adenocarcinoma

Basal cell adenoma (BCA) and basal cell adenocarcinoma (BCAC) are uncommon biphasic salivary gland tumors having morphologic similarities to other biphasic salivary gland neoplasms having differentiation toward the intercalated ducts of the salivary gland. Both tumors show mixtures of trabecular, tubular, solid, and membranous solid patterns. BCAC is separated from BCA primarily by the presence of invasion in the former. The diagnosis of BCA and BCAC is best carried out with hematoxylin and eosin-stained sections and careful attention to detail of tumors in the differential diagnosis, including adenoid cystic carcinoma, pleomorphic adenoma, and epithelial myoepithelial carcinoma.

Cytological features of basal cell adenoma of salivary glands: Analysis of 19 cases emphasizing stromal spindle cells

BACKGROUND

Basal cell adenoma (BCA) of the salivary gland is a relatively rare benign tumor. Although the presence of stromal spindle cells is a characteristic histopathological feature, this finding has not been the focus of much attention in the cytodiagnosis of BCA. Thus, we analyzed the cytological features of BCA, especially the presence of stromal spindle cells.

METHODS

Patients who were histopathologically diagnosed with BCA and underwent preoperative fine-needle aspiration cytological examination were enrolled in this study. The cytological characteristics including arrangement and shape of the neoplastic cells, nuclear and cytoplasmic features, and the presence of stromal spindle cells were reviewed.

RESULTS

Nineteen patients were enrolled in the study. The cytological specimens were cellular and composed of small or large clusters or both. The neoplastic cells had scant cytoplasm and small round to oval nuclei. Basement membrane-like material was observed in 57.9%, and peripheral palisading was noted in 84.2%. Loose aggregates of stromal spindle cells were present in 63.2%, and the stromal spindle cells shown in the histological examination of 85.7% of cases were expressed in the cytological specimens.

CONCLUSION

This study clearly demonstrated the relatively high frequency of stromal spindle cells in cytological specimens of BCA. This finding is characteristic of BCA, and therefore, the combination of cytological features, including packed clusters of neoplastic cells with scant cytoplasm and small nuclei, peripheral palisading, and basement membrane-like material, and the presence of stromal spindle cells could increase the diagnostic success of BCA.