Title

Double Trouble: Concomitant Presentation of Dual Oncocytic Neoplasms within the Thyroid Gland


Authors

Ema Mathai1, Rudolph Mosca1, Kayla Martinez2, David Bradlee DO3


Introduction

Oncocytic adenoma (OCA) is a rare thyroid tumor, accounting for less than 5% of all thyroid neoplasms. Although this condition is considered benign, oncocytic metaplasia can lead to oncocytic carcinoma1. Oncocytic carcinoma accounts for only 3% to 5% of all thyroid malignancies2. Making a preoperative diagnosis of these conditions is relatively challenging due to the lack of clinical manifestations and absence of typical imaging characteristics. Histopathological examination is often the only modality to arrive at a definitive diagnosis. Treatment for these conditions involves surgical intervention via partial or full thyroidectomy, followed by life-long thyroid hormone replacement. We present a case of oncocytic adenoma with the coexistence of oncocytic carcinoma.


Case Presentation

We present a 77-year-old man with a history of coronary artery disease with percutaneous coronary intervention, chronic obstructive pulmonary disease, and hypertension. He reported having progressive left anterior neck swelling for the past year; he was initially diagnosed with multinodular goiter one year prior. Ultrasound of the neck demonstrated a new large, solid nodule to the left thyroid lobe with multiple small nodules scattered throughout the gland. A fine needle aspiration of the left thyroid gland was performed. Pathological examination showed two distinct findings. Firstly, oncocytic carcinoma of the left lobe of the thyroid was noted, found to be 2.5 cm in greatest dimension. Secondly, an incidental finding of noninvasive follicular thyroid neoplasm with papillary-like nuclear features was noted, demonstrating an OCA. At this time, the patient’s thyroid stimulating hormone was 48.64 mclU/mL and free T4 was <0.25 ng/dL. A total thyroidectomy was performed. He tolerated this procedure well without complications.


Discussion

Oncocytic adenomas have a marked accumulation of dysfunctional mitochondria. These neoplasms are follicular in nature, with at least 75% of the tumor becoming composed of oncocytes. Oncocytes are expanded in size, with distinct cell borders, large nuclei, and appear deeply eosinophilic with a granular cytoplasm. Lack of colloid, lymphocytes, histiocytes, plasma cells and ordinary follicular cells is seen on cytologic examination of oncocytic adenomas3.

In 2022, the WHO Classification of Endocrine and Neuroendocrine Tumors was updated. According to this classification system, non-invasive follicular thyroid neoplasm with papillary-like nuclear features such as oncocytic adenomas are benign and confined to the thyroid capsule. However, oncocytic carcinoma of the thyroid contains worrisome features such as capsular or vascular invasion, marker nuclear atypia, mitosis, and pleomorphism. Thickened capsules, smaller oncocytic cells, and overall size larger than 4 cm have also been identified as signs of malignant transformation to oncocytic carcinoma3,.

The cytogenetic properties related to the formation of oncocytes includes evidence of aneuploidy. More specifically, deletions and mutations of mitochondrial DNA (mtDNA) coding for oxidative phosphorylation protein.This protein has been linked to energy production and proliferation defects in mitochondria, allowing oncocytic cells to flourish. The 4977 bp deletion has been identified frequently in oncocytic thyroid tumors. Additionally, thyroid neoplasms with oncocytes have a higher prevalence of mutations in the non-coding displacement loop region of mtDNA. The proportion of mtDNA affected by such deletions appears to be drastically higher in oncocytic carcinomas than oncocytic adenomas3,4.


References

  1. Barnabei A, Ferretti E, Baldelli R, Procaccini A, Spriano G, Appetecchia M. Hurthle cell tumours of the thyroid. Personal experience and review of the literature. Acta Otorhinolaryngol Ital. 2009 Dec;29(6):305-11. PMID: 20463834; PMCID: PMC2868205.
  2. Syed A, Vanka SA, Escudero I, Ismail R, Krayem H. Oncocytic Cell Carcinoma of the Thyroid: A Case Report and an Overview of the Diagnosis, Treatment Modalities, and Prognosis. Cureus. 2022 Oct 14;14(10):e30298. doi: 10.7759/cureus.30298. PMID: 36407154; PMCID: PMC9659316.
  3. Wei S. Oncocytic (Hürthle cell) tumors. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/thyroidhurthle.html. Accessed October 7th, 2023.
  4. Oluwole Fadare ; Giovanni Tallini. Thyroid: Oncocytic tumors. Atlas Genet Cytogenet Oncol Haematol. 2003-06-01. Online version: http://atlasgeneticsoncology.org/solid-tumor/5068/thyroid-oncocytic-tumors.