Thyroid & parathyroid

Contributed by Ayana Suzuki, C.T.

• 0 - 3% of cytologically proven benign thyroid nodules have a malignancy on resection; usually these nodules are clinically suspicious (Endocr Pract 2001;7:237, JAMA 2015;313:926, Thyroid 2007;17:1061)

Contributed by Ayana Suzuki, C.T.

• Differential with benign follicular nodule (Kini: Color Atlas of Differential Diagnosis in Exfoliative and Aspiration Cytopathology, 2nd Edition, 2011)
  • Follicular neoplasm:
    • Background: clean, sometimes hyaline colloid
    • Follicular pattern: small, uniform
    • Cytoplasm and nuclei: uniform, high N:C ratio, enlarged nuclei
  • Oncocytic follicular neoplasm:
    • Background: clean, sometimes cystic
    • Presentation: isolated, in loosely cohesive groups, sheets, syncytial tissue fragments
    • Cytoplasm and nuclei: uniform, high N:C ratio, enlarged nuclei, binucleation to multinucleation
  • Papillary thyroid carcinoma:
    • Nuclear pseudoinclusions (Orphan Annie nuclei)
• Differential with lymphocytic thyroiditis
  • Papillary thyroid carcinoma:
    • Nuclear pseudoinclusions (Orphan Annie nuclei)
  • Oncocytic follicular neoplasm:
    • Background: clean, sometimes cystic
  • MALT lymphoma:
    • Lymphoglandular bodies in the background (Acta Cytol 2018;62:93)
    • Similar chromatin pattern of lymphoid cells regardless of the difference in size
    • Absence of oncocytic cells (Acta Cytol 2018;62:93)
• Differential with granulomatous thyroiditis
  • Papillary thyroid carcinoma:
    • Nuclear pseudoinclusions (Orphan Annie nuclei) can mimic macrophages with enlarged nuclei, nuclear irregularity
  • Lymphocytic thyroiditis:
    • Absence of epithelioid histiocytes
• Differential with acute thyroiditis
  • Anaplastic carcinoma:
    • Carefully observe whether large atypical cells are present or absent
• Differential with thyroid cyst
  • Thyroglossal duct cyst (Thyroid Res & Prac 2013;10:104):
    • Cytology: proteinaceous material, inflammatory cells, rare degenerated squamous or ciliated columnar cells
    • Appropriate clinical presentation (anterior midline neck cyst, above the thyroid isthmus, below the hyoid bone)
  • Parathyroid cyst (Case Rep Surg 2015;2015:243527):
    • Cyst fluid: characteristic watery, clear gross appearance
    • Cytology: acellular or hypocellular
    • Preoperative diagnosis: elevated parathyroid hormone levels in the cyst fluid

What risk of malignancy is associated with benign thyroid cytology?

1. 0 - 3%
2. 5 - 10%
3. 12 - 15%
4. 20 - 30%
5. 40 - 50%

A. 0 - 3% Most published studies reported that a benign FNA diagnosis is associated with a very low false negative rate, estimated to be in the range of 0 - 3%. It should be noted that the precise risk of malignancy for cytologically benign nodules is difficult to assess because only a minority of these patients undergo surgery. Answers B - E are incorrect because they overestimate or exaggerate the risk of malignancy associated with benign thyroid cytology.

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Reference: Benign

What is the most likely histological diagnosis of this thyroid aspirate consistent with benign category?

1. Acute thyroiditis
2. Follicular nodular disease
3. Granulomatous thyroiditis
4. Lymphocytic thyroiditis
5. Riedel thyroiditis

C. Granulomatous thyroiditis. The absence of colloid and follicular cells in the background and the presence of multinucleated giant cells, lymphocytes and epithelioid cells suggest granulomatous thyroiditis. Answer B is incorrect because follicular nodular disease shows colloid and foam cells in the background. Answer D is incorrect because lymphocytic thyroiditis shows lymphocytes and oncocytes. Answer A is incorrect because acute thyroiditis shows numerous neutrophils. Answer E is incorrect because in Riedel thyroiditis, few cells are aspirated.

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Reference: Benign