Slide 91.Follicular adenoma, Thyroid

A. Brief Descriptions

  1. Derived from follicular epithelium.

  2. Not forerunners of cancer except in the exceptional instance.

B. Gross Findings

  1. Well demarcated nodule with a intact fibrous capsule bulging cut surface with a soft, grayish, tan, or brown appearance.

C. Micro Findings

  1. Well-vascularized tumor compression the surrounding gland.

  2. Variable secondary degenerative changes: hemorrhage, fibrosis, edema, calcification, bone formation or cystic change. (only edematous and cystic change in our slide).

  3. Intact fibrous capsule without capsular or vascular invasion.

  4. Growth pattern of tumor:

    • Solid/trabecular: cellular areas with few or no follicles formed.

    • Microfollicular: small follicles with minimal amount of colloid.

    • Normofollicular (simple): the size of the follicles approaches that of non-neoplastic glands.

    • Macrofollicular (colloid): larger follicles with full colloid.

  5. Tumor cells are polygonal with normochromatic , round to oval nucleoli; well defined cell border with moderate amount acidophilic to amphophilic cytoplasm.

D. Others :

  1. Benign encapsulated tumor composed of follicular cells.

E. Reference :

  1. Robbins Pathologic Basis of Disease, 6th ed.  P.1141.




Fig. 91-1 (2X)




Fig. 91-2 (4X)




Fig. 91-3 (20X)