Right parotid mass, FNA was suggestive of a small cell carcinoma
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Very extensive lymph node enlargement is demonstrated on the right, involving the jugular chain, the posterior triangle, supraclavicular fossa, as well as thin intra-parotid nodes in the tail of the parotid (with evidence of local extranodal spread). Abnormal enlargement also seen in the retropharyngeal space extending towards the left, and multiple enlarged left jugular chain nodes are also present in.
In the superficial parotid, superiorly, just below the level of the external acoustic meatus has an enhancing nodule measuring 10 mm. The gland is enlarged and demonstrates heterogeneous enhancement posteriorly, extending to involve the deep lobe, and extending through the skull mandibular interval which is widened.
There is no evidence of direct extension into the muscles of mastication of the parapharyngeal space. No convincing enhancement of the facial nerve is identified. Although there is some slight asymmetry in signal on the coronal post-contrast images, this asymmetry is not evident in other planes or other sequences. Similarly the trigeminal nerve, Meckel's cave and cavernous sinus appear unremarkable.
The posterior fossa, and cervical canal appeared unremarkable (limited views)
Very extensive nodal disease predominately on the right, but also crossing the midline and in the retropharyngeal space, with abnormally enhancing right parotid gland involving both superficial and deep to without convincing evidence of perineural spread.
Histology of Neck Dissection
Right parotid: A rectangular piece of firm tissue measuring 85x40x30mm. The specimen has a nodular feel to it. Upon sectioning, the specimen is comprised of normal appearing salivary tissue with well circumscribed white nodules scattered throughout. These nodules appear to arise within the parotid but are discrete from salivary tissue. There are white nodules extending out to the fatty tissue with a diameter of up to 15mm. There are nine nodules in total.
The parotid gland is infiltrated by a lobulated but unencapsulated tumour composed of polygonal cells singly, in nests and in sheets.
The predominant pattern is nested and the cells have vesicular nuclei with small nucleoli and scattered apoptoses and mitoses, but where cells are single, nuclei are more pleomorphic and the stroma is desmoplastic. Some cells have granular eosinophilic cytoplasm. No mucin is present and there are no PASd+ve granules. There are foci of necrosis. Vascular invasion is seen but no perineural infiltration is identified. A patchy chronic inflammatory cell infiltrate is present. Multiple satellite nodules are present in salivary lobules around the main mass and tumour extends to the specimen margins
In immunostains, the cells are CK5/6+, CK7+, CK20+ (focal weak), p63+ (strong focal), smA-, chromogranin-, synaptophysin-, S100+, CDX-2-, TTF-1-, WT-1-, mesothelin-, ER+ (weak 20%), PgR-.
No tumour present in lingual tonsil.
Metastatic carcinoma is present in the single facial lymph node, in the single level 1 lymph node, in all 14 level 2 nodes, nine of 10 level 3 nodes and all 15 level 3 nodes, in all three level 4 nodes, all three level 5a nodes, all nine level 5b nodes and in the single right subclavian node. There is extensive extracapsular spread and tumour is seen in small vessels in the fat around the nodes. The submandibalar salivary gland shows patchy chronic inflammation but is free of tumour.
Right parotid: Poorly differentiated adenocarcinoma extending to the specimen margins; immunophenotype consistent with, but not diagnostic of, a parotid primary. With extensive involvement of neck lymph nodes.
Key learning points:
1. It is important to differentiate intra from peri parotid masses, the latter indicating enlarged lymph nodes.
2. Diffusion restriction within lymph nodes is suspicious for neoplastic involvement.