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Open access

Haruhiko Yamazaki, Hiroyuki Iwasaki, Yoichiro Okubo, Nobuyasu Suganuma, Katsuhiko Masudo, Hirotaka Nakayama, Yasushi Rino and Munetaka Masuda

Summary

The objective this study is to report two cases of thyroid gland invasion by upper mediastinal carcinoma. Mediastinal tumors are uncommon and represent 3% of the tumors seen within the chest. In reports on mediastinal masses, the incidence of malignant lesions ranged from 25 to 49%. The thyroid gland can be directly invaded by surrounding organ cancers. We report these cases contrasting them to the case of a thyroid cancer with mediastinal lesions. Case 1 was a 73-year-old woman who was diagnosed with papillary thyroid carcinoma, and she underwent surgery and postoperative radioactive iodine. Case 2 was a 74-year-old man who was diagnosed with non-small-cell lung carcinoma, favor squamous cell carcinoma, and he underwent chemoradiotherapy. Case 3 was a 77-year-old man who was diagnosed a thymic carcinoma based on pathological findings and referred the patient to thoracic surgeons for surgical management. The images of the three cases were similar, and the differential diagnoses were difficult and required pathological examination. Primary thyroid carcinoma and invading carcinoma originating from the adjacent organs need to be distinguished because their prognoses and treatment strategies are different. It is important to properly diagnose them by images and pathological findings.

Learning points:

  • The thyroid gland in the anterior neck can be directly invaded by surrounding organ cancers.

  • Primary thyroid carcinoma and invading carcinoma originating from the adjacent organs need to be distinguished because their prognoses and treatment strategies are different.

  • It is important to properly diagnose by images and pathological findings.

Open access

Jill Pancer, Elliot Mitmaker, Oluyomi Ajise, Roger Tabah and Jacques How

Summary

Multifocal papillary thyroid carcinoma (PTC) is common and the number of tumor foci rarely exceeds ten. The mechanism of multifocal disease is debated, with the two main hypotheses consisting of either intrathyroidal metastatic spread from a single tumor or independent multicentric tumorigenesis from distinct progenitor cells. We report the case of a 46-year-old woman who underwent total thyroidectomy and left central neck lymph node dissection after fine-needle aspiration of bilateral thyroid nodules that yielded cytological findings consistent with PTC. Final pathology of the surgical specimen showed an isthmic dominant 1.5 cm classical PTC and over 30 foci of microcarcinoma, which displayed decreasing density with increasing distance from the central lesion. Furthermore, all malignant tumors and lymph nodes harbored the activating BRAF V600E mutation. The present case highlights various pathological features that support a mechanism of intraglandular spread, namely a strategic isthmic location of the primary tumor, radial pattern of distribution and extensive number of small malignant foci and BRAF mutational homogeneity.

Learning points:

  • Multifocal papillary thyroid carcinoma (PTC) is commonly seen in clinical practice, but the number of malignant foci is usually limited to ten or less.

  • There is no clear consensus in the literature as to whether multifocal PTC arises from a single or multiple distinct tumor progenitor cells.

  • Strategic location of the dominant tumor in the thyroid isthmus may favor intraglandular dissemination of malignant cells by means of the extensive lymphatic network.

  • An important pathological finding that may be suggestive of intrathyroidal metastatic spread is a central pattern of distribution with a reduction in the density of satellite lesions with increasing distance from the dominant focus.

  • PTCs originating from the isthmus with intraglandular metastatic dissemination behave more aggressively. As such, a more aggressive treatment course may be warranted, particularly with regard to the extent of surgery.

Open access

Viral Chikani, Duncan Lambie and Anthony Russell

Summary

Metastases to the pituitary gland are an uncommon complication of thyroid cancer. They resemble pituitary neoplasms posing a diagnostic challenge. We present a case of an aggressive non-radioiodine avid papillary thyroid cancer with recurrent pituitary metastases and a review of the literature. A 70-year-old woman with a history of papillary thyroid cancer and bony metastases presented with symptoms of hypoadrenalism and peripheral vision loss. Magnetic resonance imaging showed a large pituitary mass impinging on the optic chiasm. She underwent transsphenoidal resection followed by 131I ablation. Post-therapy scintigraphy showed no iodine uptake in the sellar region or bony metastases. Histology of the pituitary mass confirmed metastatic papillary thyroid cancer. Fifteen months later, she had a recurrence of pituitary metastases affecting her vision. This was resected and followed with external beam radiotherapy. Over 2 years, the pituitary metastases increased in size and required two further operations. Radioactive iodine was not considered due to poor response in the past. Progressively, she developed a left-sided III and IV cranial nerve palsy and permanent bitemporal hemianopia. There was a rapid decline in the patient's health with further imaging revealing new lung and bony metastases, and she eventually died 8 months later. To our knowledge, this is the first case of pituitary metastases from a radioiodine-resistant papillary thyroid cancer. Radioiodine-resistant metastatic thyroid cancer may exhibit rapid aggressive growth and remain poorly responsive to the currently available treatment.

Learning points

  • Differentiated thyroid cancer (DTC) has an excellent prognosis with <5% of the cases presenting with distant metastases, usually to lung and bone.

  • Metastasis to the pituitary is a rare complication of DTC.

  • The diagnosis of pituitary insufficiency secondary to pituitary metastases from DTC may be delayed due to the non-specific systemic symptoms of underlying malignancy and TSH suppression therapy for thyroid cancer.

  • The imaging characteristics of metastases to the pituitary may be similar to non-functioning pituitary adenoma.

  • Radioiodine refractory metastatic thyroid cancer has significantly lower survival rates compared with radioactive iodine-avid metastases due to limited therapeutic options.