| Three methods are currently used the assess thyroid | | | | characteristics are suggestive of papillary carcinoma: |
| nodules. These are fine needle aspiration or FNA, | | | | - nuclear inclusions, "cleared-out", "ground glass" or |
| thyroid scans, and ultrasound. Of these three, initial FNA | | | | "orphan annie" nuclei |
| is said to be more diagnostically useful and cost | | | | - nuclear "grooves" |
| effective. Although ultrasound may be able to detect | | | | - overlapping nuclei |
| nodules that cannot be detected through palpation, it is | | | | - psammoma bodies (which are rare) |
| still unable to differentiate between a malignant and | | | | - papillary projections with fibrovascular core |
| benign nodule. Thyroid scans, too, can be misleading in | | | | - "ropey" colloid |
| interpreting the malignancy of thyroid nodules. | | | | Follicular or Hurthle Cell Neoplasms |
| Fine needle aspiration biopsy is a technique wherein a | | | | The lesions in this diagnostic category express |
| sample of the tissue is aspirated using a fine needle to | | | | characteristics that could be signs of malignancy but |
| be assessed. For superficial tissue as in the thyroid, | | | | are not truly diagnostic. Factors that point to |
| breast, or prostate, the needle is unguided but for | | | | malignancy include male gender, a nodule size of more |
| deeper tissue, the needle must be guided radiologically. | | | | than 3 centimeters, and age greater than 40 years. |
| The Normal Thyroid under the Microscope | | | | Definitive diagnosis requires histologic examination of |
| Unlike other endocrine glands, the thyroid gland is | | | | the nodule to observe for capsular or vascular |
| unique in that it provides extracellular storage for its | | | | invasion. There are no genetic, histologic, or biochemical |
| products inside cyst-like follicles. These follicles contain | | | | tests to date that are routinely used to differentiate |
| thyroid hormones good enough for several weeks. | | | | between benign or malignant lesions in this category. |
| They are nearly spherical in shape and surrounded by | | | | Several studies show that thyroid peroxidase |
| a single layer of cuboidal cells. These follicles range | | | | expression as measured by the monoclonal antibody |
| from 0.2 to 0.9 mm in diameter and are filled with a | | | | MoAb 47 improves the specificity of correctly |
| substance referred to as colloid. | | | | differentiating between benign and malignant |
| Some cytophathologists believe that there must be at | | | | neoplasms in FNA specimens. Galectin-3 has also |
| least six clusters of follicular cells of 10 to 20 cells each | | | | been observed to be highly and diffusely expressed in |
| on two slides for a thyroid biopsy to qualify as benign. | | | | follicular cell neoplasms but only minimally expressed in |
| A diagnosis of malignancy can be made when there | | | | benign conditions. |
| are fewer cells, provided that there are other signs of | | | | Cytologic or histologic characteristics of a follicular |
| malignancy present in the specimen. | | | | malignancy include: |
| Cytopathologic Characteristics | | | | - minimal amounts of free colloid |
| Thyroid fine needle aspiration can be difficult and | | | | - high density cell population of either follicular or Hurthle |
| challenging as the amount of tissue on the slides for | | | | cells |
| examination may depend on the method of aspiration. | | | | - microfollicles |
| However, the evaluation of thyroid tissue should include | | | | Cytologically, these lesions may be reported as: |
| the following: | | | | - "Hurthle cell neoplasm" |
| - The presence or absence of follicles | | | | - "Suspicious for follicular neoplasm" |
| - Cell size | | | | - "Follicular neoplasm/lesion" |
| - Staining characteristics of the cells | | | | - "Indeterminate" or "non-diagnostic" |
| - Tissue polarity. This should be considered in cell block | | | | Medullary Carcinoma |
| specimens only. | | | | Fifteen percent of malignancies of the thyroid are |
| - Presence of nuclear grooves and/or nuclear clearing | | | | defined under this category. This type of thyroid |
| - Presence of nucleoli | | | | malignancy should be suspected in patients with a |
| - Presence and type of colloid | | | | family history of medullary cancer or multiple endocrine |
| - Monotonous population of either follicular or Hurthle | | | | neoplasia Type 2. |
| cells | | | | Cytologic or histologic characteristics include the |
| - Presence of lymphocytes | | | | following: |
| Benign Lesions | | | | - spindle-type cells with eccentric nuclei |
| Almost seventy percent of cases of thyroid masses | | | | - positive calcitonin stain |
| are benign lesions. Although the clinical signs in a patient | | | | - presence of amyloid |
| may favor benign lesions, FNA it does not really mean | | | | - intranuclear inclusions ( which are common) |
| that FNA should be excluded in the workup. These are | | | | Anaplastic Carcinoma |
| the following clinical characteristics of benign thyroid | | | | In less than one percent of patients with malignant |
| lesions: | | | | thyroid lesions, the diagnosis is anaplastic carcinoma. |
| - A sudden onset of pain and tenderness may | | | | This type of malignancy is more common in elderly |
| suggest hemorrhage into a benign adenoma or cyst, or | | | | patients with a fast growing thyroid mass. These |
| subacute granulomatous thyroiditis, respectively. | | | | patients may have had a slow-growing mass for |
| However, hemorrhage into a cancer may present with | | | | many years already. It is important that anaplastic |
| similar signs. | | | | carcinoma, which has limited therapy, be differentiated |
| - Symptoms suggesting hyperthyroidism or | | | | from thyroid lymphoma, for which there are ready |
| autoimmune thyroiditis (Hashimoto's disease). | | | | treatments. |
| - Family history of benign nodular disease, Hashimoto's | | | | Cytologic characteristics of anaplastic carcinoma |
| disease, or autoimmune thyroiditis. | | | | include the following: |
| - A smooth, soft, and easily movable nodule. | | | | - extreme cellular pleomorphism |
| - Multi-nodularity. | | | | - multinucleated cells |
| - A midline nodule over the hyoid bone that moves up | | | | - giant cells |
| and down with the protrusion of the tongue is most | | | | Thyroid Lymphoma |
| likely a thyroglossal duct cyst. | | | | This is a rare form of thyroid malignancy. A rapid |
| Cytological and laboratory characteristics of a benign | | | | growth of a neck mass in the location of the thyroid |
| thyroid nodule are the following: | | | | gland in an elderly patient, especially in someone with |
| - The presence of abundant watery colloid. | | | | Hashimoto's thyroiditis, is suggestive of thyroid |
| - Foamy macrophages. | | | | lymphoma. Cytologic features that could further point |
| - Cyst or cyst degeneration of a solid nodule. | | | | to this diagnosis include: |
| - Hyperplastic nodule. | | | | - monomorphic pattern of lymphoid cells |
| - Abnormal TSH levels. | | | | - positive B-cell immunotyping |
| - Lymphocytes and/or high thyroid peroxidase | | | | Although thyroid fine needle aspiration is an important |
| antibody levels. These may suggest Hashimoto's | | | | technique in the assessment of thyroid lesions, a |
| disease or in rare cases, a lymphoma. | | | | patient is always free to ask for a second opinion, |
| Malignant Lesions | | | | especially for something as serious as thyroid |
| - Papillary Carcinoma | | | | carcinoma. As pointed out earlier, it is also important for |
| Papillary carcinoma accounts for about eighty percent | | | | the examining pathologist or cytologist to differentiate |
| of malignant lesions of the thyroid. This type of | | | | between the different malignancies. A prompt and |
| malignancy includes mixed papillary and follicular | | | | correct diagnosis could spell the difference between a |
| variants like the tall cell variant and the sclerosing | | | | quality life, disability, or even death. |
| variant. Two or more of the following cytological | | | | |