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Hurthle Cell Adenoma of the Thyroid

Endocrine system

Hurthle Cell Adenoma of the Thyroid
Hurthle cell adenoma is a rare, benign neoplasm of the thyroid gland composed predominantly of Hurthle cells (also known as oncocytic or oxyphilic cells). These cells are a variant of follicular cells and are characterized by their abundant, eosinophilic, granular cytoplasm due to a high mitochondrial content.

Key Features:
• Benign Nature:
o It is a non-cancerous, encapsulated tumor. However, distinguishing it from Hurthle cell carcinoma requires careful histological evaluation, especially for evidence of capsular or vascular invasion.
• Epidemiology:
o More common in older adults and in females.
o Associated with chronic thyroiditis (such as Hashimoto’s thyroiditis).

Clinical Presentation:
• Thyroid Nodule:
o Presents as a painless, solitary nodule in the thyroid gland.
• Asymptomatic:
o Most patients are euthyroid (normal thyroid function).
• Hyperthyroidism (Rare):
o If the adenoma becomes functional (toxic), it can lead to hyperthyroidism.
• Compression Symptoms:
o Large adenomas may cause symptoms like difficulty swallowing or hoarseness.

Gross Appearance:
• Size and Shape:
o Solitary, well-circumscribed, encapsulated nodule.
• Capsule:
o Surrounded by a thick, fibrous capsule.
• Colour and Texture:
o Tan to brown or reddish cut surface, often homogenous.

• Cystic Changes:
o Occasionally shows cystic degeneration or areas of haemorrhage.

Microscopic (Histological) Features:
1. Hurthle Cells:
o Large, polygonal cells with abundant eosinophilic, granular cytoplasm.
o The cytoplasmic granularity is due to numerous mitochondria.
o Nuclei are round to oval and may show prominent nucleoli.
2. Capsule:
o A well-defined, intact capsule is essential to distinguish it from carcinoma.
3. Follicular Architecture:
o May form small follicles, but the architecture can vary from solid to trabecular.
4. Absence of Invasion:
o No capsular or vascular invasion, which differentiates it from Hurthle cell carcinoma.
5. Stroma:
o Minimal stromal involvement, but fibrosis and hyalinization can occur.

Diagnosis:
• Fine-Needle Aspiration (FNA):
o Can identify Hurthle cells but cannot distinguish between adenoma and carcinoma.
• Ultrasound:
o Shows a well-circumscribed, hypoechoic nodule.
• Histopathology (Definitive Diagnosis):
o Requires surgical excision and microscopic examination to confirm benign nature and rule out malignancy.
• Thyroid Function Tests:
o Usually normal unless the adenoma is functional

Management:
• Surgical Excision (Lobectomy):
o Indicated for definitive diagnosis and treatment.
o A total thyroidectomy may be considered if malignancy cannot be excluded.
• Observation:
o Small, asymptomatic nodules with benign cytology may be monitored.

Prognosis:
• Excellent: Since Hurthle cell adenomas are benign, surgical removal typically results in complete cure.
• Risk of Malignancy: There is a small risk that Hurthle cell adenomas can transform into Hurthle cell carcinoma, necessitating careful follow-up.



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