Microscopic Thymoma

**Semantic type:** Neoplastic Process

**Definition:** A rare type of thymoma, composed of multifocal epithelial proliferations less than 1 mm in diameter. This type of thymoma usually occurs in myasthenia gravis patients without any macroscopic (gross) evidence of tumor.

**Synonyms:** - Nodular Hyperplasia of the Thymic Epithelium