Causes of thyroid nodules

Benign	Malignant
Multinodular (sporadic) goiter ("colloid adenoma")	Papillary carcinoma
Hashimoto's (chronic lymphocytic) thyroiditis	Follicular carcinoma
Cysts (colloid, simple, or hemorrhagic)	Minimally or widely invasive
Follicular adenomas	Oxyphilic (Hürthle cell) type
Macrofollicular adenomas	Noninvasive follicular thyroid neoplasm with papillary-like nuclear features
Microfollicular or cellular adenomas	Medullary carcinoma
NIFTP (noninvasive follicular tumor with papillary-like nuclear features)*	Anaplastic carcinoma
Hürthle cell (oxyphil cell) adenomas	Primary thyroid lymphoma
Macro- or microfollicular patterns	Metastatic carcinoma (breast, renal cell, others)

* Previously called noninvasive follicular variant papillary cancer. The nodule requires surgical excision for diagnosis.

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