Follicular adenoma
It is a benign neoplasm, presenting as a single nodule, usually not greater than 3 cm in diameter. Some of them can produce thyroid hormones and consequently cause hyperthyroidism (functioning or 'hot' adenomas). The hystologic pattern may vary: macrofollicular (composed of large follicles filled with colloid), microfollicular (with smaller follicles), trabecular (with follicular cells arranged in ribbons).
Classification (no prognostic significance)