venerdì 1 febbraio 2008

Papillary thyroid carcinoma


Incidental finding on follow-up MR examination: In the left lower lobe of the thyroid, there is a hyperintense lesion on T2 STIR which was not seen on the previous exam. Ultrasound shows an irregular heterogeneous spiculated mass in the gland.

Differential Diagnosis:
- Adenoma 5-10% of nodules
- Colloid nodule
- Neoplasm
Papillary 75%
Follicular 10%
Medullary 5%
Anaplastic <5%
Hürthle cell
Metastasis (renal cell, lung, breast)

Diagnosis: Papillary thyroid carcinoma, biopsy proven

Key Points

Papillary cell is most common thyroid malignancy.
75% of thyroid malignancy.
Treated with subtotal thyroidectomy and I-131 ablation.
Typically age less than 40.
90-95% survival at 20 years.
Distant mets rare.
Local lymph node involvement does not effect prognosis.
Ultrasound is very sensitive for nodules but is not specific.

Benign US feature
- Cysts
- Solid nodule with significant cystic component
- Hyperechoic
- Peripheral hypoechoic halo
- Well defined margin
- Peripheral egg shell calcification
- Multiplicity

Suspicious US features.
- Single, solid nodule without a cystic component
- Hypoechoic
- Micro calcifications: Can be confused with inspissated colloid
- Thick peripheral halo
- Associated enlarged lymph nodes

Thyroid is very radiosensitive. As little as 10cGy may cause excess cancers.
Linear dose response curve with no evidence of a threshold at low doses.
Radiation causes an increase in all types and sizes of nodules.

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