Ectopic hamartomatous thymoma: report of a case and review of literature.

Ectopic hamartomatous thymoma (EHT) is an exceedingly rare lesion that usually arises in the lower neck and mainly affects adult men. We present the clinicopathological features of a case of EHT in a 28-year-old Chinese male, together with a literature review. Ultrasound imaging and a computed tomography (CT) scan of the neck demonstrated a 3.0-cm well-defined nodule of heterogeneous density located within the left sternocleidomastoid muscle. The patient underwent a gross total resection of the tumor. Grossly, the well-demarcated, encapsulated mass had a predominantly solid and gray-white appearance admixed with microcystic foci filled with serous content and yellowish regions. The lesion consisted of an irregular admixture of spindle cells, epithelium, and mature adipose tissue. Immunohistochemistry showed that both the spindle cell and epithelial components were diffuse and had intense nuclear positivity for p63 and cytoplasmic reactivity for pan-cytokeratin, CK7, and CK19. The patient was followed for 18 months without any evidence of metastasis or recurrence.