Follicular thyroid adenoma

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Follicular thyroid adenoma
Diagnosis in short

Follicular adenoma. H&E stain.

Synonyms follicular adenoma

LM cellular appearance (low magnification), microfollicles, thick fibrous capsule without invasion, negative for nuclear features of papillary thyroid carcinoma
LM DDx thyroid gland nodular hyperplasia, follicular thyroid carcinoma, noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), Papillary thyroid carcinoma follicular variant
Gross lesion with thick capsule
Site thyroid gland

Signs thyroid mass
Prevalence uncommon
Prognosis benign
Clin. DDx follicular carcinoma, other thyroid tumours
Treatment excision to exclude carcinoma

Follicular thyroid adenoma, abbreviated FTA, is a benign lesion of the thyroid gland.

General

  • Most common neoplasm of thyroid.[1]
  • Encapusled lesion (surrounded by fibrous capsule).
  • Cannot be diagnosed on thyroid FNA, as one cannot exclude invasion through the capsule without examining all of it.

Gross

  • Thick capsule.

Notes:

  • The entire capsule should be submitted.[2]
    • A good start for most thyroid specimens with a thick capsule is 10 blocks.

Images

Microsopic

Features:

  • Cellular.
  • Thick capsule - key feature.

Negatives.

DDx:

Images

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Left Hemithyroid, Hemithyroidectomy:
- Follicular adenoma.
- Parathyroid gland.
- Five benign lymph nodes (0/5).
- NEGATIVE for evidence of malignancy.

Block letters

LEFT THYROID, SUPERIOR POLE, EXCISION:
- FOLLICULAR ADENOMA, MAXIMAL DIMENSION 5 MM.
- LYMPHOCYTIC THYROIDITIS.
- NODULAR HYPERPLASIA.
- NEGATIVE FOR MALIGNANCY.

Micro

The section shows a well-circumscribed lesion encapsulated by a thick fibrous capsule (~0.4 mm thick).

The lesions consists of microfollicles with a dense appearing colloid. The nuclei have round regular nuclear membranes. Small indistinct nucleoli are seen at high power.

Focally, the lesional cells overlap. However, the chromatin is not cleared. Nuclear grooves are not readily apparent and nuclear pseudoinclusions are not readily identified.

See also

References

  1. Thompson, Lester D. R. (2006). Endocrine Pathology: A Volume in Foundations in Diagnostic Pathology Series (1st ed.). Churchill Livingstone. pp. 51. ISBN 978-0443066856.
  2. SR. 17 January 2011.