Lymphadenoma of the salivary gland: a rare tumour.

Lymphadenoma of the salivary gland is a very rare (or possibly even under-reported) tumour with only sparse reports found in the literature. It is not mentioned in most textbooks on salivary gland tumours or head and neck pathology. The 1996 Armed Forces Institute of Pathology fascicle briefly discusses the entity as a variant of sebaceous lymphadenoma (‘‘lymphadenoma that lacks sebaceous differentiation’’). We report a case of lymphadenoma arising from the parotid gland. A 74 year old man presented with a solitary mass in his parotid gland. A computed tomography scan suggested the possibility of pleomorphic adenoma. Fine needle aspiration was subsequently done, raising the possibility of a Warthin’s tumour. A superficial parotidectomy was then carried out for a definitive diagnosis, including a small amount of sternocleidomastoid muscle to ensure clearance. Grossly, the tumour was a well demarcated, solid grey/white mass measuring 1 cm in diameter. Microscopic examination revealed anastomosing islands of epithelial cells within a dense lymphoid stroma (fig 1). A few glandular lumina and cysts containing dense eosinophilic secretions were seen at the periphery of the nodule. No sebaceous glands were identified. There was no evidence of cytological atypia or abnormal mitotic activity. On immunohistochemistry the anastomosing cells were positive for epithelial and basal cell markers (epithelial membrane antigen, MNF116, 34BE12, and S100). The absence of sinuses and nodal capsule excluded the possibility of the tumour arising from an intraparotid lymph node. Ma et al in 2002 reported three patients with lymphadenoma of the salivary gland, all males, with ages ranging from 13 to 57 years. They noted the difficulty of diagnosing this entity, as a result of the indistinct appearance without sebaceous cells. Therefore, other tumours such as Warthin’s tumour, lymphoepithelial cysts, sebaceous lymphadenoma, metastatic carcinoma, and malignant lymphoma also need to be considered. 5 Proper recognition of this rare tumour is necessary to avoid confusion in the diagnosis. Our diagnosis in this case was confirmed by Chan, a co-author of the previously mentioned case report. Too few cases have been documented to comment on its behaviour.