A Case of Primary Aggressive Non Hodgkin’s Lymphoma of Parotid Gland

Primary lymphomas arising from the parotid gland are uncommon and usually account for only 0.6–5% of tumors or tumor-like lesions of the parotid, and therefore are commonly overlooked. Most cases involve the major salivary glands, primarily the parotid (50-93%) and the submandibular glands [1]. The misdiagnosis often leads to unnecessary diagnostic procedures thereby delaying the initiation of appropriate treatment. It is a common knowledge that it is often difficult to make distinction between lymphoma developing primarily in the parotid gland tissue or de novo in the intra-parotid lymph nodes. It has been reported that primary tumours of the parotid gland show no characteristic features on diagnostic imaging, reflecting none of their histological findings [2]. The prognosis and morphology, however, is more or less similar between the two origins [3]. In our case the main tumour was arising from the parenchyma of the deep lobe of the parotid gland. Most cases of non-Hodgkin’s lymphoma arising in salivary glands are of B-cell lineage including low-grade B-cell lymphomas of mucosa-associated lymphoid tissue (MALT), diffuse large B-cell lymphomas and follicular lymphomas [4]. It is difficult to differentiate between benign conditions from malignant tumours and therefore most patients are subjected to varied surgical procedures before a definitive diagnosis has been made. The head and neck region is the most common site where malignant lymphomas occur, but malignant lymphoma of the parotid gland is relatively rare [5]. Generally, surgeons do not anticipate primary Non Hodgkin’s Lymphoma (NHL) in the salivary glands pre-operatively and pathologists too find it difficult to give a definitive and diagnostic report based on either frozen section or fine needle aspiration biopsy (FNAB) [6]. In contrast to other extra nodal locations of NHL, parotid gland involvement is more likely to be of low grade and the patients have a better prognosis [7]. However, in our case it was of high grade. The treatment of primary parotid lymphoma includes chemotherapy and may be radiotherapy. Surgical excision is advocated only as a diagnostic tool.