Difference Between Papillary Thyroid Cancer and Follicular Thyroid Cancer.

Thyroid cancer, while relatively rare compared to other cancers, presents distinct subtypes that vary in their behavior, prognosis, and treatment. Among these subtypes, follicular thyroid cancer (FTC) and papillary thyroid cancer (PTC) are the most common forms. Both types of thyroid cancer originate from follicular cells of the thyroid gland, their differences in growth patterns, molecular characteristics, and spread patterns necessitate tailored approaches for diagnosis and management.

Comparative table:Follicular Thyroid Cancer (FTC) and Papillary Thyroid Cancer (PTC):

What is Papillary Thyroid Cancer (PTC)?

This is the most common form of thyroid cancer, accounting for approximately 80% of all thyroid cancer cases. It predominantly affects younger populations, with a higher incidence in women. The risk factors for PTC include a family history of thyroid cancer, genetic predispositions such as mutations in the RET proto-oncogene, and exposure to radiation, particularly in childhood.

Characteristics

• It commonly presents with branching papillae lined by columnar cells with clear nuclei, known as "orphan Annie" nuclei. 
• PTC often exhibits psammoma bodies, which are small, round calcified structures. 
• The cancer may also present with lymphatic spread and is typically indolent, meaning it grows slowly.
• Molecularly, PTC is frequently associated with genetic mutations, notably in the BRAF gene, this mutation is a key factor in the development of PTC and is often used as a biomarker for diagnosis and prognosis.

Symptoms

often presents as a solitary thyroid nodule, which may be discovered incidentally on imaging studies performed for unrelated reasons. 

• Patients may also present with symptoms related to local invasion, such as a palpable mass or difficulty swallowing.
•  PTC has a tendency to spread to regional lymph nodes, which can lead to lymphadenopathy.

Diagnostic Methods

The diagnosis of both PTC involves a combination of clinical evaluation, imaging studies, and histopathological examination.

• Ultrasonography is crucial in the initial assessment of thyroid nodules. It helps in identifying suspicious features such as microcalcifications, irregular margins, and increased blood flow, which may raise the suspicion of malignancy.
• Fine-Needle Aspiration (FNA) biopsy is the primary diagnostic tool for both PTC and FTC. FNA allows for cytological examination of the thyroid nodule. In the case of PTC, FNA may reveal characteristic cytological features, such as nuclear atypia and the presence of papillary structures.
• molecular testing may be employed to identify specific genetic mutations associated with PTC and FTC. For example, the presence of BRAF mutations is suggestive of PTC, 
• Thyroidectomy is often required for definitive diagnosis, as it allows for thorough histopathological examination. 

Treatment Approaches

Papillary Thyroid Cancer is generally treated with surgical intervention, typically involving a total or near-total thyroidectomy. The extent of surgery depends on the size of the tumor, its spread, and the presence of lymph node involvement. 

After surgery, patients may require radioactive iodine (RAI) therapy to eliminate any remaining cancerous cells. Thyroid-stimulating hormone (TSH) suppression therapy, using levothyroxine, is also a common approach to reduce the risk of recurrence.

What is Follicular Thyroid Cancer (FTC)?

FTC tends to occur in slightly older patients compared to PTC and also shows a higher prevalence in women. Risk factors include iodine deficiency, a history of thyroid disease, and certain genetic syndromes like Cowden syndrome.

Characteristics

• Follicular structures with a more diffuse growth pattern and lacks the papillary structures seen in PTC. 
• The cancer cells in FTC have uniform nuclei but can exhibit angioinvasion (invasion of blood vessels) and capsular invasion, which are critical for diagnosis.
• FTC is often associated with mutations in the RAS oncogene and chromosomal rearrangements involving the PTEN gene. These genetic abnormalities contribute to the cancer's development and progression.
• FTC has a lower propensity for lymphatic spread but is more likely to metastasize hematogenously, meaning it can spread through the bloodstream to distant organs such as the lungs and bones

Symptoms

• Symptoms of FTC may include 
• Palpable thyroid mass, symptoms of distant metastases, or local compressive effects.

Diagnostic Methods

The diagnosis FTC involves a combination of clinical evaluation, imaging studies, and histopathological examination.

• Ultrasonography is crucial in the initial assessment of thyroid nodules. It helps in identifying suspicious features such as microcalcifications, irregular margins, and increased blood flow, which may raise the suspicion of malignancy.
• Fine-Needle Aspiration (FNA) biopsy is the primary diagnostic tool FNA allows for cytological examination of the thyroid nodule. In the case of FTC, FNA may show follicular cells but lacks the specific papillary architecture seen in PTC.
• Molecular testing may be employed to identify specific genetic mutations associated For example, the presence of RAS mutations are associated with FTC.
• Thyroidectomy is often required for definitive diagnosis, as it allows for thorough histopathological examination. During surgery, the extent of disease, including capsular and vascular invasion, can be assessed, which is critical for the diagnosis of FTC.

Treatment Approaches

• Management may require a more individualized approach due to its propensity for hematogenous spread. 
• A total thyroidectomy is usually performed, and RAI therapy is used based on the extent of the disease and the presence of distant metastases. 
• The use of TSH suppression therapy is also recommended to minimize the risk of recurrence.

Prognosis

PTC generally has an excellent prognosis with high survival rates due to its indolent nature and effective treatment options, including surgery and radioactive iodine therapy. In contrast, FTC, while also often treatable, exhibits a more variable prognosis. FTC's outcomes depend on factors like the extent of invasion and metastasis, with more aggressive cases potentially leading to lower survival rates compared to PTC.