Basal cell adenoma of the parotid gland: Cytological diagnosis of an uncommon tumor

Abstract

Basal cell adenoma (BCA) is a rare benign epithelial tumor of the salivary gland, displaying monomorphic basaloid cells without a myxochondroid component, representing 1-3% of all salivary gland neoplasms seen predominantly in women over 50 years of age. It is uncommon in young adults. Cytodiagnosis of basaloid tumors chiefly basal cell adenoma of the salivary gland, is extremely challenging. The cytological differential diagnoses range from benign to malignant, neoplastic to non- neoplastic lesions. Histopathological examination is a must for definitive diagnosis, as these entities differ in prognosis and therapeutic aspects. We present a 22-years-old male with this uncommon diagnosis with a discussion on the role of cytological diagnosis. Fine needle aspiration cytology is a simple, minimally invasive method for the preoperative diagnosis of various types of neoplastic and non-neoplastic lesions. The knowledge of its pitfalls and limitations contributes to a more effective approach to treatment.

Keywords: Basal cell adenoma; basal cell adenocarcinoma; basaloid tumor; cytological diagnosis.

Figure 1

(a) Clinical examination: Small nodule behind the left ear. Cytological smears showing (b) basaloid cells in nests sheets and trabeculae (PAP stain; ×100). (c) peripheral palisading of cells (red arrows) and bare nuclei in background (PAP, x400)); (d) basement membrane material around cell clusters (green arrows) (PAP, x400)

Figure 2

(a) Gross examination: Tumor with a solid homogenous grey-white lobulated cut surface. (b-d) Histological sections showing basaloid cells with uniform round-oval nuclei, eosinophilic cytoplasm and indistinct cytoplasmic borders arranged in tubulo-trabecular pattern separated by collagenous stroma and peripheral palisading within the nests. (H&E stain, (b) x200, (c) x400, (d) x400)