Endocrinology · Thyroid Neoplasms
The facts most likely to be tested
Papillary thyroid carcinoma is the most common type of thyroid malignancy and is strongly associated with a history of childhood head and neck radiation.
Histopathology reveals characteristic Orphan Annie eye nuclei (clear, ground-glass nuclei) and psammoma bodies (laminated calcifications).
The presence of nuclear grooves and intranuclear cytoplasmic inclusions are classic diagnostic features on fine-needle aspiration.
Papillary thyroid carcinoma typically spreads via the lymphatic system to regional cervical lymph nodes rather than hematogenously.
The BRAF V600E mutation is the most frequently identified genetic alteration associated with this malignancy.
Initial management for most patients involves total thyroidectomy or lobectomy depending on tumor size and risk stratification.
Post-operative management often includes radioactive iodine (I-131) ablation for patients with high-risk features or evidence of metastatic disease.
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A 34-year-old female presents for evaluation of a painless, firm thyroid nodule discovered during a routine physical exam. She has no history of neck pain, dysphagia, or hoarseness, and her TSH level is within normal limits. She reports a history of radiation therapy for acne as a child. Ultrasound reveals a 1.5 cm hypoechoic nodule with microcalcifications. Fine-needle aspiration biopsy demonstrates cells with ground-glass nuclei and nuclear grooves.
What is the most likely diagnosis?
Papillary thyroid carcinoma
The combination of a history of childhood radiation, microcalcifications on ultrasound, and pathognomonic 'Orphan Annie eye' nuclei on biopsy is diagnostic for papillary thyroid carcinoma.
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Etiology / Epidemiology
Most common thyroid cancer (80%); associated with prior head/neck radiation.
Clinical Manifestations
Painless, firm, fixed thyroid nodule; Orphan Annie eye nuclei on histology.
Diagnosis
Fine needle aspiration (FNA) is the gold standard for initial evaluation.
Treatment
Total thyroidectomy is the treatment of choice for most patients.
Prognosis
Excellent prognosis with >95% 10-year survival rate.
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Epidemiology & Etiology
Represents the most common thyroid malignancy, typically occurring in patients aged 30-50. Significant risk factors include ionizing radiation exposure to the head or neck during childhood. It is significantly more common in females, reflecting a 3:1 female-to-male ratio.
Pertinent Anatomy
Originates from the follicular cells of the thyroid gland. The tumor often spreads via the lymphatic system to regional cervical lymph nodes, which is a common site of early metastasis.
Pathophysiology
Driven by RET/PTC rearrangements or BRAF mutations. Histology reveals characteristic psammoma bodies (laminated calcifications) and Orphan Annie eye nuclei (clear, ground-glass chromatin). The tumor is typically slow-growing and well-differentiated.
Clinical Manifestations
Patients usually present with a painless, firm, fixed thyroid nodule. Hoarseness or dysphagia may indicate local invasion of the recurrent laryngeal nerve or esophagus. Cervical lymphadenopathy is a common finding at presentation.
Diagnosis
The Fine needle aspiration (FNA) biopsy is the diagnostic test of choice for any suspicious nodule. Thyroid function tests (TSH) are typically normal. Ultrasound features suggesting malignancy include microcalcifications, hypoechogenicity, and irregular margins.
Treatment
Surgical resection via Total thyroidectomy is the standard of care. Post-operative radioactive iodine (I-131) ablation is indicated for high-risk patients or those with distant metastasis. Levothyroxine is used for TSH suppression therapy to prevent recurrence.
Prognosis
Prognosis is excellent, with a >95% 10-year survival rate. Patients require lifelong monitoring of serum thyroglobulin levels to detect potential recurrence.
Differential Diagnosis
Follicular Thyroid Carcinoma: hematogenous spread rather than lymphatic
Medullary Thyroid Carcinoma: associated with elevated calcitonin and MEN 2 syndromes
Anaplastic Thyroid Carcinoma: rapidly enlarging, fixed mass with poor prognosis
Thyroid Adenoma: benign, encapsulated, usually non-tender
Hashimoto Thyroiditis: diffuse enlargement, positive anti-TPO antibodies