Thyroid micropapillary cancer

Thyroid carcinoma is the most common malignancy of the endocrine system.

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer, accounting for 70-90% of well-differentiated thyroid malignancies.

Thyroid papillary microcarcinoma is a subtype of papillary carcinoma that included tumors with less than 10mm diameter.

Prevalence is increasing.

Thyroid carcinoma incidence of approximately 9/100,000 per year.

These cancers have a behavior that ranges from incidentally detected and clinically inconsequential microcarcinomas to aggressive and poorly treatable anaplastic malignant neoplasms.

Most thyroid cancers present as thyroid nodules that are either asymptomatic or associated with local cervical symptoms or adenopathy.

Less often, thyroid cancers first present with manifestations of metastatic disease.

Papillary and follicular thyroid cancers arise from follicular epithelium and often retain responsiveness to TSH, produce thyroglobulin, and concentrate iodide.

The mean age at diagnosis is 45 yr.

Papillary thyroid carcinoma does occur in children and increases in incidence with age.

Most of PTMC are not detectable at clinical examination and are diagnosed incidentally during pathologic examination of thyroid specimens after surgery for benign thyroid diseases, or in autopsies.

Characteristic cytologic features of PTC help make the diagnosis by FNA or after surgical resection, include psammoma bodies, cleaved nuclei with an “orphan-Annie” appearance caused by large nucleoli, and the formation of papillary structures.

Widespread use and the technical improvement of thyroid ultrasonography and fine-needle aspiration biopsy (FNAB) contributed to an increase in the rate of preoperative diagnosis of PTMC over the last few decades.

With the widespread use of ultrasound, the detection rate for small thyroid nodules continues to increase.

Fine-needle aspiration biopsy is useful for cancers larger than 10mm, and microcarcinomas may be detected by this method.

Thyroid cancer incidence rates have been steadily increasing all over the world, due to higher detection of papillary thyroid microcarcinoma

Tumor size ranged between 0.1-10 mm with mean of 5.9 mm.

A mean of 19.3% of patients were positive for family history.

A mean of 3% have a history of radiation exposure.

Expression of molecular characteristics in PTMC Fas ligand positivity, BRAFV600E mutation, P53 gene expression and cyclin D1 positivity.

Other factors reported include: CK-19, HBME-1, galectin-3 expression in 98.7%, TSHR mRNA(40) in 59.4%, RET gene rearrangement in 52.3%, Bcl-2 expression in 94.8%, Bax expression in 74.3%, S100A4in 68.6%, P27 gene expression in 36.8%, MUC1 gene expression in 48.4%, FDG positivity in 55% and finally surviving positivity in 66.6% of patients were positive.

Up to 43% of all thyroid cancers are papillary thyroid microcarcinomas (PTMCs) and nearly 50% of new cases of papillary thyroid carcinoma (PTC) are PTMCs.

PTMC is a type of PTC with a maximum diameter of 1.0 cm or less.

Usually characterized by benign behavior, of little clinical significance, and do not affect patients’ survival, however PTMCs show diverse disease extent with widely varying reported frequencies of the aggressive features.

These tumors are usually encountered during the histopathologic examination of the thyroid glands removed during necropsy or surgery for nonthyroid or nonmalignant thyroid disease.

It may occasionally be the primary lesion of a lymph node metastasis presenting clinically as a neck mass

High-resolution ultrasound-guided fine needle aspiration biopsy has led to a rapid rise in the incidence of papillary thyroid microcarcinoma.

Most PTMCs have an indolent course and excellent prognosis,although some are thought to be associated with recurrence, distant metastasis, or mortality

PTMCs may even behave like benign lesions which can justify a minimalist therapeutic approach.

Less than 1% cause-specific mortality rate at 20 years, it frequently spreads to the cervical lymph nodesand may occasionally metastasize to distant sites.

Patients have very low mortality, however, 4-16% of patients with PTMC develop recurrent disease with many of these patients developing distant metastasis.

The mean rate of tumor related mortality was 1.7% and rate of recurrence or distant metastasis after follow-up was 6%.

PTMC is often multifocal from 15.5–40% in surgical series and over 80% in systematic autopsy studies.

PTMC extrathyroidal tumor extension, a factor correlated with a higher risk of locoregional recurrence, is also observed in 10–20% in surgical and pathologic studies.

PTMC has a considerable rate of lymph node metastasis to the central compartment.

Central compartment LN metastasis in PTMC is associated with a risk of disease recurrence and is a reliable prognostic factor.

Central LNM was significantly related to bilaterality.

Standard treatment for these tumors remains controversial.

Some consider PTMC to be a less aggressive subset of papillary thyroid cancers that require only minimal treatment.

Others report a high incidence of metastasis from microcarcinomas and thus favor an aggressive surgical approach followed by ablation therapy.

Total or near-total thyroidectomy is performed when tumor foci is preoperatively detected in a bilateral lobe.

In PTMC confined to the unilateral lobe, two options are applicable: total thyroidectomy vs. unilateral lobectomy

It is debatable whether total thyroidectomy or lobectomy is the appropriate treatment for patients with PTMC.

American Thyroid Association guidelines, the recommended treatment in patients with isolated PTMC at low risk consists of thyroid lobectomy, whereas near-total or total thyroidectomy is considered the treatment of choice in patients with a history of radiation therapy to the head and neck or a first-degree member with differentiated thyroid cancer or age greater than 45 years

In patients with aggressive PTMC need a radical therapeutic approach, as classical PTC, based on total thyroidectomy, lymphadenectomy, central compartment, and radioiodine therapy.

Few studies have been able to demonstrate a clinical benefit of I-131 therapy for patients with PTMC.

Aggressive PTMC treatments can cause adverse outcomes, such as surgical damage to the recurrent laryngeal nerve, hypoparathyroidism, and the development of new primary cancers after radioiodine treatments.

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