Thymic Epidermoid Cyst: Clinical and Imaging Manifestations of This Rare Anterior Mediastinal Mass

Table 1

Differential diagnosis of an anterior mediastinal mass.

	CT	PET/CT	MRI	Enhancement pattern
Thymic epidermoid cyst	Heterogeneous	Not FDG avid	Heterogenous	Possible restricted diffusion on DWI
Thymic hyperplasia	Homogenous, soft tissue attenuation	Mildly FDG avid; difficult to exclude malignancy due to physiologic uptake in the thymus	Homogenous	Loss of signal on out of phase
Teratoma	Heterogenous, may contain fat/calcification	Not FDG avid	Heterogenous, may contain fat and calcification	Heterogenous
Thymic neoplasm	Focal mass; possible metastases, local invasion, and/or lymphadenopathy	Mildly FDG avid; difficult to exclude malignancy due to physiologic uptake in the thymus	Focal mass; possible metastases, local invasion, and/or lymphadenopathy	T1 isointense to muscle/normal thymus; heterogenous on T2WI
Lymphoma	Enlarged, heterogeneously enhancing mass	FDG avid	Heterogenous, could be necrotic	Shows enhancement