Spindle Epithelial Tumor With Thymus-Like Differentiation in an Infant.

Spindle epithelial tumor with thymus-like differentiation (SETTLE) is an extremely rare malignant neoplasm. Here we describe an infant girl with sublingual SETTLE. Diagnosis was complicated by initial histopathology result from incisional biopsy showing features of chronic sialadenitis. Gross total resection of the lesion demonstrated a low-grade spindle epithelial cell neoplasm, which was confirmed to be SETTLE on specialist pathology review. Previous literature has not identified a case occurring at such a young age or involving a tumor located outside the thyroid gland.