title: Five Top Stories in Thyroid Pathology.
abstract: BACKGROUND
  Thyroid carcinoma is the most common malignant tumor of endocrine organs, yet it only accounts for approximately 1% of all cancers in the United States with more than 35,000 new cases diagnosed each year and more than 450,000 people living with this disease. While most tumors can be diagnosed without much difficulty, a few tumor types, especially tumors with follicular pattern, sometimes pose a diagnostic challenge.
  
  
  OBJECTIVE
  To discuss morphologic, immunohistochemical, and molecular features of thyroid tumors. We also explore the clinicopathologic features of papillary microcarcinoma and medullary microcarcinoma and how the latter is related and differentiated from C-cell hyperplasia. Finally with the ever-growing list of organ systems involved in immunoglobulin (Ig) G4-related diseases, we discuss the still not completely explored IgG-4-related thyroid disease.
  
  
  METHODS
  Data were obtained from review of the pertinent peer-reviewed literature and institutional experience.
  
  
  CONCLUSIONS
  Histomorphologic evaluation still remains the gold standard for diagnosis in most cases of thyroid diseases. The application of ancillary studies such as immunohistochemistry and molecular diagnosis, including next-generation sequencing, is becoming more common.
authors.affiliation: From the Department of Pathology, University of Massachusetts Memorial Medical Center, Worcester (Drs Moghaddam, Sakhdari, Cosar, and Khan);
authors.forename: Parnian Ahmadi
authors.initials: PA
authors.lastname: Moghaddam
authors.affiliation: and the Department of Pathology, Yale School of Medicine, New Haven, Connecticut (Drs Virk and Prasad).
authors.forename: Renu
authors.initials: R
authors.lastname: Virk
authors.affiliation: From the Department of Pathology, University of Massachusetts Memorial Medical Center, Worcester (Drs Moghaddam, Sakhdari, Cosar, and Khan);
authors.forename: Ali
authors.initials: A
authors.lastname: Sakhdari
authors.affiliation: and the Department of Pathology, Yale School of Medicine, New Haven, Connecticut (Drs Virk and Prasad).
authors.forename: Manju L
authors.initials: ML
authors.lastname: Prasad
authors.affiliation: From the Department of Pathology, University of Massachusetts Memorial Medical Center, Worcester (Drs Moghaddam, Sakhdari, Cosar, and Khan);
authors.forename: Ediz F
authors.initials: EF
authors.lastname: Cosar
authors.affiliation: From the Department of Pathology, University of Massachusetts Memorial Medical Center, Worcester (Drs Moghaddam, Sakhdari, Cosar, and Khan);
authors.forename: Ashraf
authors.initials: A
authors.lastname: Khan
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007150:Immunohistochemistry; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000235:genetics
chemical_list: D014408:Biomarkers, Tumor