Ectopic cervical thymus: case report.

Ectopic cervical thymus is rarely considered in the differential diagnosis of cervical masses: this lesion is essentially asymptomatic and generally occupies a position in the neck along the carotid sheath, underneath the sterno-cleido-mastoid muscle. It is supposed that most of these masses arise as a consequence of migration defects during glandular embryogenesis. Ectopic thymus rarely invades contiguous structures but in the literature some cases of malignant transformation of aberrant cervical thymus have been reported. Some non-invasive investigations (MRI, ultrasonography) are useful but accurate diagnosis depends eventually on surgical excision and histologic examination.