Hürthle cell

Hürthle cell
Other names	Askanazy cell
MicrographshowingHürthle cellsin a Hürthle cell neoplasm.Pap stain.
Pronunciation	/ˈhɪərtlə/
Specialty	Pathology

AHürthle cellis a cell in thethyroidthat is often associated withHashimoto's thyroiditisas well as benign and malignant tumors (Hürthle cell adenomaandHürthle cell carcinoma,formerly considered a subtype offollicular thyroid cancer). This version is a relatively rare form of differentiated thyroid cancer, accounting for only 3-10% of all differentiated thyroid cancers.Oncocytesin the thyroid are often called Hürthle cells. Although the terms oncocyte, oxyphilic cell, and Hürthle cell are used interchangeably, Hürthle cell is used only to indicate cells of thyroid follicular origin.

Diseases

Cytopathology suspicious forHürthle cell neoplasm(Bethesda categoryIV, rather than Hürthle cell hyperplasia), Pap stain.

Hürthle cell neoplasmscan be separated into Hürthle cell adenomas and carcinomas, which are respectively benign and malignant tumors arising from the follicular epithelium of the thyroid gland.Themitochondrial DNAof Hürthle cell carcinoma contain somatic mutations.Hürthle cell carcinomas consists of at least 75% Hürthle cells.Chronic lymphocytic thyroiditis or Hashimoto's thyroiditis, along with cases of long-standingGraves' disease,show Hürthle cells present.

Diagnosis

Hürthle celladenomasare most likely diagnosed much more frequently than Hürthle cell carcinomas. The female to male ratio for Hurthle cell adenomas is 8:1, while the ratio is 2:1 for the malignant version.Hürthle cell cancer tends to occur in older patients. The median age at diagnosis for Hürthle cell carcinomas is approximately 61 years old.Typically a painless thyroid mass is found in patients with this type of cancer.As expected, patients with carcinoma usually present larger tumors than patients with adenoma. Rarely, the cancer can spread to the lymph nodes.On few occasions, patients with Hürthle cell carcinoma have distant metastases in the lungs or surrounding bones.Hürthle cell neoplasms are somewhat difficult to differentiate between being benign or malignant. Since the size and growth pattern of the tumor cannot be used to determine malignancy, although larger tumors have higher incidence of malignancy, Hürthle cell adenomas and carcinomas have to be separated by the presence, in the case of carcinomas, or absence, in the case of adenomas, of both capsular invasion and vascular invasion.Tumors displaying only capsular invasion tend to behave less aggressively than those with vascular invasion.Hürthle cell carcinomas are characterized as either minimally invasive or widely invasive tumors. While the minimally invasive or encapsulated carcinoma is fully surrounded by a fibrous capsule, the widely invasive carcinoma shows extensive area of both capsular and vascular invasion with the leftover capsule typically difficult to identify.Classification is important since widely invasive tumors can have outcomes with a 55% mortality rate.

Histology

Hürthle cells arise from the follicular epithelium. Key features of these oncocytic cells include a granularcytoplasmthat stains eosinophilic (pink onH&E stain) and a vesicular nucleus with a large nucleolus.A Hürthle cell is larger than a follicular cell, and its cellular material stains eosinophilic. Hürthle cells also tend to be large, polygonal cells with distinct cell borders.The cytoplasm of the oncocytes in Hürthle cell adenomas and carcinomas is characterized by an eosinophilic granular nature, which is commonly due to the oncocytes' high content ofmitochondria.Some of these cells can contain up to 5,000 mitochondria, which fills the cytoplasm to the point of nearly excluding other organelles.This high amount of mitochondria is reported to be a result of mutations in the mitochondrial DNA.Some scientists have identified these mutations as deletions in the mitochondrial DNA of Hürthle cells found in neoplasms and Hashimoto's thyroiditis.

Treatment

A non-minimally invasive Hürthle cell carcinoma is typically treated by a totalthyroidectomyfollowed by radioactive iodine therapy.A Hürthle cell adenoma or a minimally invasive tumor can be treated by a thyroidlobectomy,although some surgeons will perform a total thyroidectomy to prevent the tumor from reappearing and metastasizing. A modified radical neck dissection may be performed for clinically positive lymph nodes.

History

The Hürthle cell is named after German histologistKarl Hürthle,who investigated thyroid secretory function, particularly in dogs.However, this is a misnomer since Hürthle actually describedparafollicular C cells.The cell known as the Hürthle cell was first described in 1898 byMax Askanazy,who noted it in patients withGraves' disease.

See also

• Adenoma
• Oncocytoma
• Oxyphil cell

External links

• EndocrineWebat endocrineweb.com
• HKUat hku.hk
• Imageat upmc.edu