A 40 year old female presented with painless mass on left side of neck, biopsy of which was done from referring place. As the report was not available, FNAC of the mass was done, which was pleomorphic adenoma of left parotid gland. MRI of the mass showed large heterogeneous mass in relation to the superficial lobe of left parotid gland. The mass was contiguous with the carotid sheath at the medial margin. Parotidectomy was done as frozen section was positive for malignancy. Histopathology report of the resected specimen turned out to be Non Hodgkin’s Lymphoma - Diffuse Large B-cell Type and Tumour Cells were positive for LCA and CD 20.

Introduction

Primary lymphoma of parotid gland is relatively rare and occurs in 1-5% of tumours where parotid gland is the original site of tumour.1 It has been reported that 80-85% of parotid gland tumours are benign and 15-20% are malignant.2 90% of salivary gland lymphomas present as firm painless swelling and more than 90% occurs in parotid gland.3 It is believed that the differentiation of the malignant lymphoma originating in the parotid gland from other tumours including benign tumour is difficult; however, some authors have reported that malignant lymphomas shows tumour homogeneity surrounded by well defined margins and were rarely associated with necrosis.4,5

Generally, among lymphomas, non Hodgkin’s lymphoma is more common in parotid gland, frequently B-cell type.6

Treatment of primary lymphoma of parotid includes parotidectomy, radiotherapy and/or chemotherapy depending upon the grade of tumour, clearance of margin and associated lymphadenopathy and pre-op confirmed diagnosis of lymphoma.

Case Report
A 40 year old female presented with painless swelling in left side of neck since 3 months incisional biopsy of the swelling (90% of Parotid lymphomas present as firm painless swelling) was done from the referring place, but histopathology report was not available (Fig. 1). Fresh FNAC of the swelling from our centre showed pleomorphic adenoma. There was no history suggestive of facial nerve involvement. The swelling was fixed to the surrounding structures and sternocleidomastoid muscle also to the previous incision site. There was no history of rapid increase of swelling. MRI of the swelling revealed a large heterogeneous lobulated mass in relation to the superficial lobe of left parotid gland along with inferior margin with extension to the infrahyoid neck (Fig. 2). The deep lobe was normal. The mass was contiguous with the left carotid sheath at the medial margin. Extension to the subcutaneous tissue was noted.

While the patient was being worked up in ward, she developed a middle jugular lymphadenopathy of 2 x 2 cm in size.

Superficial parotidectomy was carried out with excision of lymph node (Fig. 3) and the procedure was uneventful without any evidence of facial nerve damage. Histopathology of the mass turned out to be Non Hodgkin’s lymphoma - diffuse large B-Cell type, positive for LCA and CD20 (Fig. 4).

After receiving the histopathology, USG abdomen and bone marrow study was done. There was no evidence of lymphadenopathy elsewhere in the body. There was no involvement of bone marrow with lymphoma.

Biopsy of the lymph node came as Non Hodgkin’s lymphoma.

Following these reports, patient was put on chemotherapy (Chop regime)

Fig. 1 : Parotid swelling with scar of previous incisional biopsy and lymph node in posterior triangle, which appeared later.	Fig. 2 : MRI of Parotid Gland tumour showing the heterogeneous mass in relation to the superficial lobe of left Parotid Gland.
Fig. 3 : Cut surface of Parotid Gland tumour.	Fig. 4 : Microscopic appearance of lymphoma of Parotid Gland.

Discussion

Lymphoma originating in the parotid gland is rare and occurs in 1-5% of tumours where parotid gland is the original site of tumour.1 About 80-85% of parotid gland tumours are benign and 15-20% are malignant.2 90% of salivary gland lymphomas present as firm painless swelling and more than 90% occurs in parotid gland.3 The differentiation of lymphoma originating in the parotid gland from other tumours, including benign tumours is difficult, however, some authors have reported that malignant lymphomas show tumour homogeneity surrounded by well defined margins and are rarely associated with necrosis.4,5 In general malignant lymphoma originating the parotid gland is histologically described as low grade non Hodgkin’s lymphoma, frequently belonging to the B - Cell type.4

If the lymphoma is confined to the parotid gland, treatment is by parotidectomy with postop radiotherapy. If there is evidence of spread beyond salivary gland, treatment is by polychemotherapy, according to protocol, this protocol being followed in our case.

References

1. Nagata M, Kumazawa H, Iwai H, et al. Study of malignant lymphoma in the parotid gland region, Nippon Jibiinkouka Gakkai Kaiho 1996; 99 : 918-25 (in Japanese).
2. Batsakis JG. Tumour of the head and neck, 2nd edn. Baltimore: Williams and Wilkins, 1979 : 2-75.
3. Baily and Love’s short practice of surgery 23rd edition, John D Langdon, Salivary Gland disorders, chap. 42, page no. 660.
4. Hashida I, Tamaki Y, Sakurai H, et al. Malignant lymphoma of the parotid gland: a study of six cases. Gann no Rynsho 1995; 41 : 863-7 (in Japanese).
5. Hyman Ga, Wolff M. Malignant lymphoma of the salivary glands. Am J Clin Pathol 1976; 65 : 421-38.
6. Tabor EK, Curtin HD. MR of the salivary glands. Radiol Clin North Am 1989; 27 : 379-92.