title: Thyroid Paraganglioma: Our Experience and Systematic Review of the Literature on a Rare Tumor.
abstract: Primary paraganglioma (PG) of the thyroid gland is an extremely rare neuroendocrine tumor with potential for misdiagnosis. We describe 2 cases of thyroid PG, suggest a possible diagnostic and therapeutic management strategy, and present a systematic review of the literature.
  
  
  
  Two 67-year-old women presented similarly with asymptomatic but rapidly growing thyroid nodules in which malignancy was suspected after fine needle aspiration biopsy, "THY 4" according to the 2014 SIAPEC classification, both undergoing total thyroidectomy. Unexpectedly, immunohistochemistry showed neuroendocrine cellular architecture that was negative for common markers of well-differentiated follicular neoplasms, thyroglobulin, thyroid transcription factor 1, cytokeratins and medullary thyroid cancer, calcitonin, carcinoembryonic antigen, whereas neuron-specific enolase, synaptophysin, chromogranin A, and S-100 protein were highly expressed, confirming the diagnosis of primary thyroid PG. The patients were both discharged on postoperative day 2, without any other therapy and are currently well without evidence of local recurrence of metastatic disease, after 4 years and 3 months of follow-up, respectively.
  
  
  
  These are the only 2 cases of thyroid PG experienced in our center which specializes in thyroid surgery. Thyroid PG is a rare neuroendocrine neoplasm first described by Van Miert in 1964 with just over 50 cases reported in the literature. Our experience is concordant with the literature that the diagnosis of the primary PG of the thyroid is challenging, due to its low prevalence and the cytologic and histopathologic similarities with other more frequently diagnosed benign and malignant thyroid tumors. Immunohistochemistry is required for definitive diagnosis but gross tumor characteristics are also helpful for diagnosis. Surgical resection is the recommended standard treatment.
authors.affiliation: Departments of Surgical Oncologic and Gastroenterologic Sciences (DiSCOG).
authors.forename: Maria Rosa
authors.initials: MR
authors.lastname: Pelizzo
authors.affiliation: Departments of Surgical Oncologic and Gastroenterologic Sciences (DiSCOG).
authors.forename: Christian
authors.initials: C
authors.lastname: Conti
authors.affiliation: Medical Diagnostic Sciences and Special Therapies, University of Padova, Padova.
authors.forename: Gianmaria
authors.initials: G
authors.lastname: Pennelli
authors.affiliation: Medical Physics Unit, Department of Services of Diagnosis and Cure.
authors.forename: Elena
authors.initials: E
authors.lastname: Bellan
authors.affiliation: Department of Cancer Imaging, Division of Imaging Sciences and Biomedical Engineering, King's College London, St Thomas' Hospital, London, UK.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Cook
authors.affiliation: Department of Nuclear Medicine and Radiology, University of Michigan Hospital, Ann Arbor, MI.
authors.forename: Ka Kit
authors.initials: KK
authors.lastname: Wong
authors.affiliation: Department of Radiology, University of Southern California, Los Angeles, CA.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Colletti
authors.affiliation: Departments of Surgical Oncologic and Gastroenterologic Sciences (DiSCOG).
authors.forename: Isabella
authors.initials: I
authors.lastname: Merante Boschin
authors.affiliation: Department of Nuclear Medicine, Radiology, Interventional Radiology, NeuroRadiology, Medical Physics, Clinical Laboratory, Biomarkers Laboratory, Microbiology, Pathology, 'Santa Maria della Misericordia Hospital,' Rovigo, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Rubello
mesh_terms: D000368:Aged; D019468:Disease Management; D005260:Female; D006801:Humans; D010235:Paraganglioma / Q000175:diagnosis / Q000601:surgery*; D011379:Prognosis; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000601:surgery*; D013965:Thyroidectomy