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Pathology - Thyroid carcinomas
Definition • A collection of malignant epithelial tumors originating in the thyroid gland. Four principal kinds are identified: papillary, follicular, medullary, and anaplastic.
Epidemiology • Rare, constituting around 1% of all cancers in wealthy nations. The average age of diagnosis is mid-40s to early 50s for the papillary type, 50s for the follicular and medullary forms, and 60s for the anaplastic type. Aetiology • Radiation exposure is a recognized risk factor for thyroid carcinoma, particularly papillary carcinoma. Iodine deficiency is also a contributing factor, especially in follicular carcinomas. Approximately 25% of medullary carcinomas are associated with inherited disorders, specifically multiple endocrine neoplasia (MEN) types 2A and 2B, as well as familial medullary thyroid cancer (FMTC).
Carcinogenesis: RET and TRK mutations are characteristic of papillary carcinomas. Follicular carcinomas typically exhibit RAS mutations. TP53 mutations are prevalent in anaplastic carcinomas. Presentation: Most well-differentiated thyroid carcinomas manifest as a solitary thyroid nodule. Thyroid function is typically normal.
Anaplastic carcinoma typically manifests as a swiftly expanding cervical mass; encroachment on adjacent structures results in hoarseness, dysphagia, and dyspnea. Macroscopy: Papillary carcinomas typically present as firm, grey-white lumps with uneven boundaries. They are frequently multifocal.
Follicular carcinomas are typically encapsulated, spherical solid tumors exhibiting a tan to brown hue.
Medullary carcinomas are solid grey-white to tan tumors, frequently characterized by a gritty texture.
Anaplastic carcinomas are substantial necrotic tumors that typically supplant the thyroid and extensively infiltrate surrounding tissues.
Cytopathology
Papillary carcinoma aspirates comprise papillaroid fragments of follicular epithelial cells exhibiting the distinctive nuclear characteristics of papillary carcinoma, such as powdered chromatin, thick nuclear membranes, nuclear grooves, and nuclear pseudoinclusions. Multinucleated giant cells, psammoma bodies, and dense colloid may be observed.
Follicular carcinoma aspirates are cellular, comprising follicular epithelial cells found individually and in microfollicular configurations. It is important to note that these appearances are indistinguishable from follicular adenomas; cytological analysis cannot differentiate between these entities
Medullary carcinoma aspirates are cellular, with loosely cohesive epithelial cells that may be either round or spindle-shaped. Certain cells may have eccentric nuclei, resulting in a plasmacytoid morphology. The nuclei have coarsely granular chromatin. Amyloid fragments may be observed.
Anaplastic carcinoma aspirates have considerable cellularity, with significantly abnormal malignant cells.
Histopathology
Papillary carcinoma is characterized by distinct nuclear features: oval form, overlapping, chromatin clearance, nuclear grooves, and pseudoinclusions. While the majority of tumors exhibit a papillary form, this characteristic is not essential for diagnosis.
Follicular carcinoma is an invasive follicular tumor devoid of the nuclear characteristics associated with papillary thyroid carcinoma. Follicular carcinomas are categorized into two primary types: slightly invasive and broadly invasive.
Minimally invasive tumors have restricted capsular invasion and/or vascular invasion.
Extensively invasive tumors exhibit extensive infiltration of the thyroid and/or vascular structures.
Medullary carcinoma exhibits sheets, nests, or trabeculae of rounded or spindle-shaped neoplastic cells characterized by granular cytoplasm and nuclei containing coarse chromatin. Amyloid deposits may be observed. The diagnosis can be validated by immunoreactivity for calcitonin.
Anaplastic carcinomas consist of extremely pleomorphic epithelioid and spindle-shaped cells. Significant necrosis is observed, and vascular blockage by tumor is prevalent.
Prognosis: Papillary carcinomas and less invasive follicular carcinomas are low-grade malignancies characterized by an excellent prognosis. Extensively invasive follicular carcinomas and medullary carcinomas are intermediate-grade neoplasms associated with an elevated risk of metastasis and mortality. Anaplastic carcinomas are exceedingly malignant and nearly usually result in death within months of diagnosis.
TNM 7 pathological staging of thyroid carcinomas Primary tumour (T)
pT1a: tumour d 10mm in size, limited to the thyroid.
pT1b: tumour d 20mm, but > 10mm in size, limited to the thyroid.
pT2: tumour > 20mm, but d 40mm in size, limited to the thyroid.
pT3: tumour > 40mm in size, limited to thyroid, or any tumour with
minimal extrathyroid extension.
pT4a: tumour of any size extending beyond the thyroid capsule to
invade subcutaneous soft tissues, the larynx, trachea, oesophagus, or
recurrent laryngeal nerve.
pT4b: tumour invades the prevertebral fascia, mediastinal vessels, or
encases the carotid artery.
2 Note that all anaplastic tumours are considered T4.
Regional lymph nodes (N)
pN0: no regional lymph node metastasis.
pN1a: metastases in level VI cervical lymph nodes.
pN1b: metastases in levels I–V cervical, retropharyngeal, or superior
mediastinal lymph nodes
Definition • A collection of malignant epithelial tumors originating in the thyroid gland. Four principal kinds are identified: papillary, follicular, medullary, and anaplastic.
Epidemiology • Rare, constituting around 1% of all cancers in wealthy nations. The average age of diagnosis is mid-40s to early 50s for the papillary type, 50s for the follicular and medullary forms, and 60s for the anaplastic type. Aetiology • Radiation exposure is a recognized risk factor for thyroid carcinoma, particularly papillary carcinoma. Iodine deficiency is also a contributing factor, especially in follicular carcinomas. Approximately 25% of medullary carcinomas are associated with inherited disorders, specifically multiple endocrine neoplasia (MEN) types 2A and 2B, as well as familial medullary thyroid cancer (FMTC).
Carcinogenesis: RET and TRK mutations are characteristic of papillary carcinomas. Follicular carcinomas typically exhibit RAS mutations. TP53 mutations are prevalent in anaplastic carcinomas. Presentation: Most well-differentiated thyroid carcinomas manifest as a solitary thyroid nodule. Thyroid function is typically normal.
Anaplastic carcinoma typically manifests as a swiftly expanding cervical mass; encroachment on adjacent structures results in hoarseness, dysphagia, and dyspnea. Macroscopy: Papillary carcinomas typically present as firm, grey-white lumps with uneven boundaries. They are frequently multifocal.
Follicular carcinomas are typically encapsulated, spherical solid tumors exhibiting a tan to brown hue.
Medullary carcinomas are solid grey-white to tan tumors, frequently characterized by a gritty texture.
Anaplastic carcinomas are substantial necrotic tumors that typically supplant the thyroid and extensively infiltrate surrounding tissues.
Cytopathology
Papillary carcinoma aspirates comprise papillaroid fragments of follicular epithelial cells exhibiting the distinctive nuclear characteristics of papillary carcinoma, such as powdered chromatin, thick nuclear membranes, nuclear grooves, and nuclear pseudoinclusions. Multinucleated giant cells, psammoma bodies, and dense colloid may be observed.
Follicular carcinoma aspirates are cellular, comprising follicular epithelial cells found individually and in microfollicular configurations. It is important to note that these appearances are indistinguishable from follicular adenomas; cytological analysis cannot differentiate between these entities
Medullary carcinoma aspirates are cellular, with loosely cohesive epithelial cells that may be either round or spindle-shaped. Certain cells may have eccentric nuclei, resulting in a plasmacytoid morphology. The nuclei have coarsely granular chromatin. Amyloid fragments may be observed.
Anaplastic carcinoma aspirates have considerable cellularity, with significantly abnormal malignant cells.
Histopathology
Papillary carcinoma is characterized by distinct nuclear features: oval form, overlapping, chromatin clearance, nuclear grooves, and pseudoinclusions. While the majority of tumors exhibit a papillary form, this characteristic is not essential for diagnosis.
Follicular carcinoma is an invasive follicular tumor devoid of the nuclear characteristics associated with papillary thyroid carcinoma. Follicular carcinomas are categorized into two primary types: slightly invasive and broadly invasive.
Minimally invasive tumors have restricted capsular invasion and/or vascular invasion.
Extensively invasive tumors exhibit extensive infiltration of the thyroid and/or vascular structures.
Medullary carcinoma exhibits sheets, nests, or trabeculae of rounded or spindle-shaped neoplastic cells characterized by granular cytoplasm and nuclei containing coarse chromatin. Amyloid deposits may be observed. The diagnosis can be validated by immunoreactivity for calcitonin.
Anaplastic carcinomas consist of extremely pleomorphic epithelioid and spindle-shaped cells. Significant necrosis is observed, and vascular blockage by tumor is prevalent.
Prognosis: Papillary carcinomas and less invasive follicular carcinomas are low-grade malignancies characterized by an excellent prognosis. Extensively invasive follicular carcinomas and medullary carcinomas are intermediate-grade neoplasms associated with an elevated risk of metastasis and mortality. Anaplastic carcinomas are exceedingly malignant and nearly usually result in death within months of diagnosis.
TNM 7 pathological staging of thyroid carcinomas Primary tumour (T)
pT1a: tumour d 10mm in size, limited to the thyroid.
pT1b: tumour d 20mm, but > 10mm in size, limited to the thyroid.
pT2: tumour > 20mm, but d 40mm in size, limited to the thyroid.
pT3: tumour > 40mm in size, limited to thyroid, or any tumour with
minimal extrathyroid extension.
pT4a: tumour of any size extending beyond the thyroid capsule to
invade subcutaneous soft tissues, the larynx, trachea, oesophagus, or
recurrent laryngeal nerve.
pT4b: tumour invades the prevertebral fascia, mediastinal vessels, or
encases the carotid artery.
2 Note that all anaplastic tumours are considered T4.
Regional lymph nodes (N)
pN0: no regional lymph node metastasis.
pN1a: metastases in level VI cervical lymph nodes.
pN1b: metastases in levels I–V cervical, retropharyngeal, or superior
mediastinal lymph nodes
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