Poster Presentation ESA-SRB 2023 in conjunction with ENSA

Synchronous metastatic thyroblastoma and metastatic lung adenocarcinoma (#346)

Karen Van 1 , Shan Balachandran 1 , Rosemary Wong 1 , Michael Mond 1
  1. Eastern Health, Box Hill, VIC, Australia

CASE STUDY

A 44-year-old previously well man, an ex-smoker, with no pertinent family history, presented with a palpable right thyroid nodule and associated right cervical lymphadenopathy.

Thyroid ultrasonography identified a 47mm solid, hypoechoic right thyroid nodule, with anterior triangle and supraclavicular fossa lymphadenopathy. FNA confirmed a Bethesda 6 cytology suggestive of medullary carcinoma with a right lymph node positive for neoplasia. Serum calcitonin was <1.3pmol/L (RR <4.3). FDG-PET imaging demonstrated FDG-avidity of the right thyroid mass and right cervical lymphadenopathy. Small, non-PET-avid pulmonary nodules were identified bilaterally. Two-stage thyroidectomy with right modified radical neck dissection was performed due to patient preference. Histology indicated a high-grade malignancy with mixed epithelial and spindle cell components including a significant primitive component, and involving 17/38 lymph nodes. Limited somatic mutation analysis did not identify common thyroid cancer driver mutations. 

Seven months later, he developed transient haematuria and dyspnoea. Whilst no cause for the haematuria was identified, a moderate left pleural effusion with multiple pulmonary nodules were suggestive of metastases. He underwent VATS and pleurodesis. Lung wedge resection showed invasive mucinous adenocarcinoma favouring a primary lung malignancy.

Following specialist opinion, the original thyroid carcinoma was determined consistent with metastatic thyroblastoma. He is currently undergoing chemotherapy for both malignancies and awaiting genetic screening for DICER1.

 

DISCUSSION

Thyroblastoma is a thyroid malignancy recognised as a discrete entity in the 5th Edition WHO Classification of Endocrine and Neuroendocrine Tumours.1 Previously classified as malignant thyroid teratomas, molecular analysis has now allowed for definitive differentiation of benign/immature and malignant thyroid teratomas.2Thyroblastomas are histologically defined by the presence of primitive multilineage elements, including immature thyroid epithelium, cellular mesenchyme with frequent rhabdomyoblastic differentiation, and neuro- epithelial blastema.2 All 11 reported cases are associated with DICER1 mutations.3 We present a case with two distinct malignancies, with thyroblastoma being a unique, novel entity.

  1. Baloch ZW, Asa SL, Barletta JA, et al (2022) Overview of the 2022 WHO Classification of Thyroid Neoplasms. Endocr Pathol 33:27-63.
  2. Rooper LM. From Malignant Thyroid Teratoma to Thyroblastoma: Evolution of a Newly-recognized DICER1 -associated Malignancy. Adv Anat Pathol. 2023 Mar 1;30(2):136-145.
  3. Guilmette J, Dias-Santagata D, Lennerz J, Selig M, Sadow PM, Hill DA, Nosé V. Primary Thyroid Neoplasm with Fetal Morphology Associated with DICER1 Mutations: Expanding the Diagnostic Profile of Thyroblastoma. Thyroid. 2022 Nov;32(11):1423-1428.