Follicular thyroid adenoma

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

General

• Most common neoplasm of thyroid.
• Encapusled lesion (surrounded by fibrous capsule).

Gross

• Thick capsule.

Notes:

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

Microsopic

Features:

• Cellular.
• Thick capsule - key feature.

Negatives.

• No invasion of the capsule - see follicular thyroid carcinoma.
• No nuclear features suggestive of papillary thyroid carcinoma.

DDx:

• Thyroid gland nodular hyperplasia with an encapsulated nodule - not as cellular.
• Follicular thyroid carcinoma.

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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

• Thyroid gland.