ONCOCYTIC/HURTHLE CELL CARCINOMA OF THE THYROID
Case provided by Amy Stein, MD
The patient is an 86 year old woman who noticed a painless lump in her neck seven months prior to admission. An ultrasound at that time showed an enlarged left thyroid lobe (6 cm compared to the right side which was 4.1 cm) which was diffusely enlarged and heterogeneous with some cystic spaces but without discrete nodules. A repeat ultrasound was performed five months later which showed that the left lobe had increased to 7.3 cm in size, though it otherwise showed similar characteristics to the prior ultrasound. A fine needle aspirate of the left thyroid followed by left thyroidectomy was performed.
The fine needle aspirate showed a hypercellular specimen consisting of a predominance of oncocytic/Hurthle cells characterized by cells with abundant granular cytoplasm (stained blue in Papanicolaou stain) in single cells, microfollicles, and sheets with only scant colloid. The interpretation was suspicious for follicular neoplasm with Hurthle cell change. The lobectomy specimen showed a Hurthle cell carcinoma consisting of oncocytic/Hurthle cells with abundant pink granular cytoplasm (on Hematoxylin & Eosin stain) with a predominantly solid growth pattern which had foci of capsular and vascular invasion.
ONCOCYTIC/HURTHLE CELL CARCINOMA
Follicular carcinoma is the second most common type of thyroid carcinoma representing approximately 15% of thyroid carcinomas. Most follicular carcinomas are of the conventional type, with only 20-25% having a Hurthle cell or oncocytic appearance. The incidence of follicular carcinoma increases with age, particularly in oncocytic/Hurthle cell carcinoma in which the majority are diagnosed in patients over the age of 60. The risk for follicular carcinoma increases in areas of iodine deficiency and in patients with pre-existing benign thyroid lesions such as benign thyroid nodules, adenomas, and goiter. Hurthle cell carcinoma consists of tumor cells with abundant granular eosinophilic cytoplasm (oncocytic cells) due to the presence of numerous mitochondria. All follicular carcinomas require capsular or vascular invasion. A greater number of oncocytic encapsulated follicular neoplasms qualify as carcinoma based upon capsular or vascular invasion compared to follicular neoplasms with conventional histology. Approximately 20% of oncocytic neoplasms meet the criteria for a diagnosis of carcinoma. In the U.S., the 10 year survival for oncocytic carcinoma is 73-76% which is somewhat worse than that for conventional follicular carcinoma which is 83-86%. This may reflect differences in behavior including lymph node metastases as well as possibly higher recurrence rate and tumor-related mortality. In addition, poorer outcomes for patients with oncocytic/Hurthle cell carcinoma may reflect their typically older age. Risk factors which are associated with a greater likelihood of metastasis include tumor size (greater than 4 cm), trabecular or solid growth, mitotic activity, and greater than three foci of angioinvasion.
This patient will be seen several weeks following surgery at a tertiary care center for further treatment recommendations.
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