The “atypia of undetermined significance/follicular lesion of undetermined significance” (AUS/FLUS) category, known as Bethesda Category III, has been ascribed a malignancy risk of 5–15%, but the probability of malignancy in AUS/FLUS specimens remains unclear.
In grades 0–3, the malignant risk of thyroid nodules is extremely low, less than 5%; while the malignant risk of thyroid nodules in grade 4 and above increases sharply, and the final risk is 100%, because thyroid nodules in grade 6 are all pathologically confirmed thyroid cancer.
Atypical thyroid biopsy (atypia of undetermined significance or follicular lesion of undetermined significance, AUS/FLUS): this happens when there are some abnormal/atypical cells in the biopsy sample but not enough to diagnose a cancer.
A primary or metastatic malignant neoplasm affecting the thyroid gland.
Bethesda category IV nodules are described as follicular neoplasm or suspicious for follicular neoplasm (FN/SFN).
Bethesda category III includes the cytological findings: “atypia of undetermined significance” (AUS) and “follicular lesion of undetermined significance” (FLUS), while Bethesda category IV represents “follicular neoplasm/suspicious for follicular neoplasm”.
A follicular adenoma is a benign encapsulated tumor of the thyroid gland. It is a firm or rubbery, homogeneous, round or oval tumor that is surrounded by a thin fibrous capsule. A follicular adenoma is a common neoplasm of the thyroid gland. In two autopsy series, the incidence of thyroid adenoma was 3 and 4.3% [1, 2].
Biopsy results can fall within one of six categories as defined by the Bethesda system for reporting FNA cytopathology results: I (non-diagnostic), II (benign), III (atypia of undetermined significance/follicular lesion of undetermined significance), IV (follicular neoplasm), V (suspicious for malignancy), and VI ( ...
[5] The thyroid follicles are the structural and functional units of a thyroid gland. These are spherical, and the wall is made up of a large number of cuboidal cells, the follicular cells. These follicular cells are the derivates of the endoderm and secrete thyroid hormone.
ICD-10 code: C73 Malignant neoplasm of thyroid gland.
E04. 1 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes. The 2022 edition of ICD-10-CM E04.
ICD-10 code E04. 1 for Nontoxic single thyroid nodule is a medical classification as listed by WHO under the range - Endocrine, nutritional and metabolic diseases .
Neoplasm of uncertain behavior of thyroid gland 1 D44.0 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes. 2 The 2021 edition of ICD-10-CM D44.0 became effective on October 1, 2020. 3 This is the American ICD-10-CM version of D44.0 - other international versions of ICD-10 D44.0 may differ.
The 2022 edition of ICD-10-CM D44.0 became effective on October 1, 2021.
A primary malignant neoplasm that overlaps two or more contiguous (next to each other) sites should be classified to the subcategory/code .8 ('overlapping lesion'), unless the combination is specifically indexed elsewhere.
In these biopsies not enough thyroid cells were obtained to render a diagnosis. This can happen when a cyst is aspirated or when the specimen is almost entirely composed of blood. This accounts for 10 percent of the biopsies, even in the most experienced hands. Generally a repeat biopsy is needed several weeks after the first one.
In this category, the specimen was adequate and the cytopathologist can definitively call the nodule benign. Diagnoses that fall into this category include benign follicular nodules (includes adenomatoid nodules, and colloid nodules), lymphocytic (Hashimoto) thyroiditis, and granulomatous (subacute) thyroiditis.
Biopsies in this category are adequate specimens, but the features seen on cytology are not diagnostic of either a benign process or of a tumor. The general recommendation is to repeat the fine needle aspiration biopsy in 6 weeks. The risk of malignancy in this category is in the range of 5 to 15%.
Nodules in this category are tumors. Most of these will turn out to be follicular adenomas which are benign. However, needle biopsy cannot distinguish between benign and malignant follicular tumors. For this reason, nodules in this category typically require surgical removal to make a definitive diagnosis.
Nodules in this category are very suspicious for malignancy, but the cytopathologist does not see all of the required features to make a definitive diagnosis. Because of the high risk of malignancy, the general recommendation is to remove the entire thyroid. The risk of malignancy is 60 to 75%.
In this category, the cytopathologist sees all of the features necessary to make the diagnosis of malignancy. Patient with nodules in this category should undergo removal of the entire thyroid. The risk of malignancy is 97 to 99%.
1 Hospital Universitario Reina Sofía (Endocrinology and Nutrition Service), Córdoba, Spain; 2 Hospital Universitario Reina Sofía (Radiology Service), Córdoba, Spain.
1 Hospital Universitario Reina Sofía (Endocrinology and Nutrition Service), Córdoba, Spain; 2 Hospital Universitario Reina Sofía (Radiology Service), Córdoba, Spain.