CASE 13931 Published on 28.08.2016

Papillary carcinoma of thyroid. US and MRI features of U5 rare malignant variant thyroid cancer

Section

Head & neck imaging

Case Type

Clinical Cases

Authors

Fahad Mewazy Al-Hamidi, Aikaterini Ntoulia, Mark Owen

Withybush General Hospital,
Hywel Dda Health Board,
Radiology;
Email: Fahad.Mewazy@wales.nhs.uk
Patient

29 years, female

Categories
Area of Interest Head and neck ; Imaging Technique Ultrasound, Ultrasound-Colour Doppler, MR
Clinical History
A 29-year-old woman was referred by her GP for neck ultrasound complaining of a palpable lump in the right lower neck, growing for 4 months. No associated hoarseness.
Imaging Findings
Thyroid ultrasound revealed diffuse enlargement of the right thyroid lobe with heterogeneous hypoechoic echotexture consistent with a malignant thyroid lesion. No focal nodules were noted. There were multiple intralesional microcalcifications. Colour Doppler imaging demonstrated increased vascularity. The left thyroid lobe and isthmus were normal. Regional lymphadenopathy with hyperechoic echotexture at levels III and IV showed profuse internal vascularity. No definite microcalcification was seen within the nodes.
MRI neck was performed to evaluate the full extent of the lesion and regional lymphadenopathy. Images demonstrated a large enhancing mass arising from the right lobe of the thyroid gland associated with abnormal ipsilateral level III and IV lymph nodes.
Initial FNA was reported as follicular variant papillary thyroid carcinoma. There was concern regarding lymphoma or anaplastic tumour on imaging and subsequent core biopsy revealed diffuse sclerosing variant of papillary carcinoma. No family history of thyroid cancer or MEN.
Discussion
Thyroid cancer constitutes 5%–7% of all thyroid nodules. Histologically most malignant lesions are papillary carcinoma (70-80%) followed by follicular (5-10%), medullary (5-10%) and anaplastic (1-2%). Primary lymphoma and sarcoma are rare [4, 5]. Papillary carcinomas are conventional and variant: tall cell, diffuse sclerosing (3-6%), solid, and follicular [18-20].
Clinical presentation includes a painless neck lump, hoarse voice, difficulty in swallowing and cervical lymphadenopathy [1].

Ultrasound is a very sensitive imaging modality for detection and characterization of thyroid nodules, however, no single ultrasound feature is pathognomonic. Ultrasound morphological criteria are considered more accurate for predicting malignant thyroid nodules than size [3-5, 9]. Most thyroid cancers are focal and rarely present as a diffuse infiltrative mass. When this occurs, anaplastic carcinoma and lymphoma should be considered.

There are several ultrasound scoring systems such as the American Thyroid Association Professional Guidelines, the Thyroid Imaging Reporting and Data System (TIRADS) Scoring System and recently the British Thyroid Association Guidelines for the Management of Thyroid Cancer. The latter uses the U1 – U5 Classification system to grade thyroid nodules. U1-U5 is based on grey scale ultrasound morphologic criteria and colour Doppler findings and is widely used for assessing the risk of malignancy and predicting the need for FNAC [5-9, 17].
Ultrasound appearances of benign nodules (U1–U2) should be regarded as reassuring and do not require fine needle aspiration cytology, unless the patient is at high risk of malignancy. If the US appearances are indeterminate or suspicious of malignancy (U3–U5), ultrasound guided FNAC should follow [9].
Recently elastography has been used to image the thyroid. There is increasing evidence that elastography is useful in U2/U3 lesions to up or downgrade those requiring FNA [10-12].

Neck CT or MRI (avoiding iodinated contrast agents) has no role in routine imaging of solitary thyroid nodules and is indicated to evaluate extrathyroid extension of thyroid cancer, and to assess metastases to the mediastinal or cervical lymph nodes [10, 13, 14].

Total thyroidectomy is the treatment of choice for well-differentiated thyroid carcinoma. After total thyroidectomy, patients undergo radioiodine scanning for detection of regional or distant metastatic disease, followed by radioablation of any residual disease. For nodal involvement, therapeutic lymph node dissection is required [8-9, 14-15]. External beam radiotherapy is indicated for patients with recurrent or residual disease [1, 9].

Papillary and follicular carcinoma have a good prognosis, medullary carcinoma intermediate prognosis, and anaplastic carcinoma poor prognosis [1, 9, 16]. Papillary cancer variants are usually associated with more aggressive clinical behaviour [19].
Differential Diagnosis List
Follicular variant of papillary carcinoma (proved by pathology).
Papillary carcinoma
Follicular carcinoma
Anaplastic thyroid carcinoma
Lymphoma
Chronic lymphocytic thyroiditis
Final Diagnosis
Follicular variant of papillary carcinoma (proved by pathology).
Case information
URL: https://www.eurorad.org/case/13931
DOI: 10.1594/EURORAD/CASE.13931
ISSN: 1563-4086
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