Parotid gland non-Hodgkin lymphoma

Case contributed by Ammar Ashraf

Presentation

Slowly growing left neck swelling for one year. Intermittent fever, anorexia, and 10 kg weight loss in the last year.

Patient Data

Age: 50 years
Gender: Female
ultrasound

A well-defined multiseptated cystic lesion is seen in the superficial portion of the left parotid gland. Some internal vascularity is appreciable in the lesion on the color Doppler ultrasound examination. The possible differential includes Warthin tumor, pleomorphic adenoma, or less likely an organizing abscess

A well-defined lesion, measuring about 26 x 25 mm is seen in the superficial lobe of the left parotid gland. It is of low signal intensity on T1 and T2-weighted images and of high signal intensity on STIR images when compared with the normal gland. The lesion shows minimal enhancement on the post-contrast images. Multiple small bilateral cervical lymph nodes are seen. The parotid lesion is likely a Warthin tumor, with possible differential diagnosis of a pleomorphic adenoma.

Gallium-67 whole body scan

Nuclear medicine

Increased radiotracer accumulation is noted in the area of the left parotid gland (primary lesion?). Multiple focal areas of increased radiotracer uptake are also noted in the dorsolumbar spine, right 8th/9th rib posterolaterally, the right shoulder joint, and bilateral femoral shafts. Normal gallium uptake is noted in the liver and spleen (which appear mildly enlarged), gut, and bone marrow. 

  • Microscopy of fine needle aspiration cytology (FNAC) of the left parotid lesion: Atypical lymphoid hyperplasia; however, the possibility of a neoplastic lesion (like lymphoma) cannot be excluded and an excisional biopsy is advised for better assessment.
  • The patient underwent left superficial parotidectomy and its histopathology showed atypical lymphoproliferative process consistent with non-Hodgkin lymphoma, follicular B-cell type grade II.
  • Immunohistochemistry: Strong positive reaction by B-cell markers (CD79a and CD20).  Bcl-6, Bcl-2, and CD10 are also very strongly positive. CD23 highlights follicular dendritic cell meshwork. Cyclin-D1, CD138, AE1/3, and SMA are negative by the tumor cells. CD3 & CD5 are positive in the background T-cells. Ki-67 proliferative index is approximately 30%.  EBV staining is negative. Diagnosis: 
  • Bone marrow biopsy: Heavily infiltrated with a lymphoma; its cell type needs to be immunophenotyped by flow cytometry and by cytogenetics and molecular analysis.

Case Discussion

Approximately 2% of all salivary gland tumors are primary non-Hodgkin lymphoma (NHL) and 75% of these lymphomas are seen in the parotid gland. Extra-nodal marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT), follicular B-cell lymphoma, and diffuse large B-cell lymphoma are the commonest subtypes of the NHL found in the salivary glands. The prognosis of different NHLs of the salivary gland depends on the histological subtypes and clinical stages. Lymphomas arising from the nodes are associated with a worse prognosis than those arising from the parenchyma. The extra-nodal marginal zone B-cell lymphoma of the MALT type (MALT lymphoma) is considered to have a favorable outcome than other histological subtype lymphomas (non-MALT lymphoma). In addition, the differentiation between parotid lymphoma and salivary gland epithelial tumors (benign or malignant) is vital due to marked differences in their management; e.g. chemotherapy and radiotherapy are the treatment options in the parotid NHL whereas parotid epithelial tumors are usually treated surgically.

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