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thyroid oncocytic tumors

Friday 7 December 2007

thyroid oncocytic tumor, Hurthle cell neoplasms of the thyroid; thyroid Hurthle cell tumor

Types

- thyroid oncocytic adenoma (Hurthle cell adenoma )
- thyroid oncocytic carcinoma (Hurthle cell carcinoma )

Digital cases

Thyroid oncocytic adenoma

- JRC:1175 : Thyroid oncocytic adenoma (Hurthle cell adenoma).
- JRC:14913 : Thyroid oncocytic adenoma (Hurthle cell adenoma).

Thyroid oncocytic carcinoma

- JRC:2669 : Anaplastic (squamous cell) carcinoma, arising from a preexisting Hurthle cell neoplasm.
- JRC:14583 : Minimally invasive Hurthle cell carcinoma.
- JRC:14616 : Minimally invasive Hurthle cell carcinoma.
- JRC:18761 : Hurthle cell carcinoma thyroid metastatic to vertebrae.
- JRC:18922 : Thyroid follicular carcinoma, oxyphil cell variant.

Anaplastic carcinoma in a Hurthle cell tumor

- JRC:15040 : Anaplastic carcinoma, squamous type, allegedly arising in a Hurthle cell neoplasm.

Papillary oncocytic thyroid tumors

Many Hürthle cell tumours, whether benign or malignant, show papillary change, which is really a pseudopapillary phenomenon, because Hürthle cell tumours have only scant stroma and may fall apart during manipulation, fixation, and processing.

True oxyphilic or Hürthle cell papillary carcinoma has been reported to comprise from 1% to 11% of all papillary carcinomas.

These tumours have a papillary architecture, but are composed predominantly or entirely of Hürthle cells.

The nuclei may exhibit the characteristics of usual papillary carcinoma, or they may instead resemble the pleomorphic nuclei of Hürthle cells, being large, hyperchromatic, and pleomorphic.

The clinical behaviour of this rare subtype is controversial; some authors have reported that they behave like typical papillary carcinomas, whereas others maintain that the Hürthle cell morphology confers a more aggressive behaviour, with higher rates of 10 year tumour recurrence and cause specific mortality.

This suggestion of aggressive behaviour may be attributed to the inclusion of tall cell variant papillary carcinomas in the group of Hürthle cell carcinomas.

Oncocytic papillary carcinoma is an accepted diagnosis when the tumour has complex papillary architecture with thin papillae that have true fibrovascular cores, and the papillae are lined predominantly or entirely by Hürthle cells.

Some papillary carcinomas composed of oncocytic cells have a pronounced stromal chronic inflammatory cell infiltrate.

The diagnosis of Hürthle cell follicular variant papillary carcinoma remains controversial.

The application of ret/PTC analysis by reverse transcription polymerase chain reaction (RT-PCR) allowed the recognition of a follicular variant of Hürthle cell papillary carcinoma as a group of lesions with no invasive behaviour at the time of diagnosis but which harboured a ret/PTC gene rearrangement.

Many of these lesions exhibit irregularity of architecture, with hypereosinophilic colloid and nuclear features of papillary carcinoma, but these can be obscured by the hyperchromasia and prominent nucleoli of oncocytic change.

Nevertheless, they can be recognised when there is a high index of suspicion and with the addition of immunohistochemistry for HBME-1, galectin-3, cytokeratin 19 (CK19), and ret, or by RT-PCR studies of ret rearrangements.

These tumours have the potential to metastasise, explaining the occurrence of malignancy in patients with a histopathological diagnosis of adenoma.

Warthin-like tumour of the thyroid

These lesions resemble Warthin’s tumour of the salivary glands and therefore have been called “Warthin-like tumour of the thyroid”. They harbour the characteristic nuclear atypia of papillary carcinoma. Unlike the true Warthin’s tumour, these thyroid neoplasms have malignant potential.

Because of a characteristic cystic change and extensive lymphocytic infiltration into the cores of the papillae of the tumour, one morphological subtype of Hürthle cell papillary carcinoma has a striking histological resemblance to papillary cystadenoma lymphomatosum of the salivary gland and has been called “Warthin-like tumour of the thyroid”.

This lesion occurs in the setting of chronic lymphocytic thyroiditis, predominantly in women, and has a similar prognosis to usual papillary carcinoma.

Management

The management of Hürthle cell carcinoma is controversial.

In most institutions, patients undergo total thyroidectomy followed by radioactive iodine. Iodine uptake by these lesions tends to be poor.

External beam radiotherapy is advocated only for locally invasive disease. There is no evidence that oncocytic follicular variant papillary carcinomas behave differently to their non-oncocytic counterparts.

Some authors have reported that the more aggressive oncocytic carcinomas that behave as follicular carcinomas with widespread metastatic spread have a worse prognosis that do non-oncocytic follicular carcinomas matched for stage and patient parameters; this might be attributable to the reduced capacity for radioactive iodine uptake that these lesions may exhibit.

The loss of effectiveness of this targeted treatment results in increased morbidity and mortality.

Open References

- My approach to oncocytic tumours of the thyroid. Asa SL. J Clin Pathol. 2004 Mar;57(3):225-32. PMID: 14990587 [Free]

- Bonora E, Evangelisti C, Bonichon F, Tallini G, Romeo G. Novel germline variants identified in the inner mitochondrial membrane transporter TIMM44 and their role in predisposition to oncocytic thyroid carcinomas.Br J Cancer. 2006 Dec 4;95(11):1529-36. PMID: 17088905

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