Parotid lymphoma: involving parotid tail
Tender parotid lump.
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A multi-lobulated mass or cluster of smaller masses lies just postero-inferior to the right parotid gland, wrapping around the anterior aspect of sternocleidomastoid and deviating the parotid gland anterolaterally.
This lobulated lesion does involve the tail of the right parotid gland. The mass shows high T2 signal, enhancement and diffusion restriction.
The surrounding subcutaneous soft tissue show mild T2 hyperintensity and mild enhancement.
Linear enhancement is seen within the posterior aspect of the right parotid gland of uncertain nature-it is possible that this represents a segment of the right facial nerve.
No definite abnormal enhancement of the facial nerve within the petrous temporal bone.
Mildly enlarged submandibular nodes are evident bilaterally and there is mild prominence of the left jugulodigastric node.
- Enhancing, multi-lobulated mass arising largely posteroinferior to the right parotid gland but involving the parotid tail consistent with multiple enlarged lymph nodes.
- Mildly enlarged submandibular and left jugulodigastric node.
- Neoplastic etiology is favored. Differential diagnosis includes nodal metastases and lymphoma.
Right parotid biopsy: A wedge-shaped piece of rubbery fawn/yellow tissue 4mm in maximum dimension. Indicative of dense fibrotic chronic inflammation. No tumour.
Right posterior parotid biopsy: Similar appearance to above.
Right parotid: Paraffin sections of the specimen submitted for frozen section shows dense fibrous tissue infiltrated by chronic inflammatory cells. No evidence of tumour is seen.
Right posterior parotid: The sections show infiltration of adipose and fibrous tissue and skeletal muscle by a population of atypical large lymphoid cells arranged in diffuse sheets. These have round and oval vesicular nuclei, many with conspicuous nucleoli and a narrow rim of pale cytoplasm. Moderate numbers of mitotic figures are identified. Strong membrane staining for CD20 is seen in the majority of atypical cells and there is strong nuclear staining for bcl-6 and patchy moderate cytoplasmic staining for bcl-2. The atypical cells are negative for CD3, CD5, CD10, CD23, cyclin D1, ALK-1 and cytokeratin AE1/AE3. The features are of non Hodgkin's diffuse large B cell lymphoma.
Right parotid biopsy: Dense fibrosis and chronic inflammation.
Right posterior parotid biopsy: non Hodgkin's diffuse large B cell lymphoma.
Key learning points:
- It is important to differentiate intra- from peri parotid-masses, the latter indicating enlarged lymph nodes.
- Diffusion restriction within lymph nodes is suspicious for lymphoma.