Reevaluating the nature of thymic lipofibroadenoma: A case report with hamartomatous features and a literature review

Rationale: Thymic lipofibroadenoma (LFA) is an extremely rare benign thymic tumor of mixed epithelial and mesenchymal origin, whose pathological nature remains incompletely understood. This case presents a unique thymic lesion combining classic LFA features with a novel lobulated, ductal-forming epithelial proliferation, prompting a reevaluation of its classification. Patient concerns: A 68-year-old male nonsmoker with a 10-year history of hypertension was admitted following a motor vehicle accident. Chest computed tomography incidentally revealed a well-circumscribed, heterogeneous mass (55 × 38 × 65 mm) in the right anterior mediastinum, containing both soft-tissue and adipose components. The patient had no specific symptoms related to the mass. Diagnoses: Histological examination showed a biphasic architecture: areas resembling classic thymic LFA with anastomosing bland epithelial strands within a fibroadipose stroma, and a novel component with lobulated hyperplastic epithelium exhibiting ductal differentiation and bilayered glandular structures. Immunohistochemically, epithelial cells were diffusely positive for CK5/6 and p63; ductal structures showed a bilayered pattern (CK7+/p63− luminal cells; p63+ basal cells). The Ki-67 proliferation index was low (<2%). No cytologic atypia, mitosis, or necrosis was seen. Based on the composite hamartomatous morphology, the lesion was diagnosed as a thymic hamartoma. Interventions: The tumor was completely excised via a transxiphoid single-port thoracoscopic approach. The postoperative recovery was uneventful. Outcomes: At 21-month follow-up, the patient remained disease-free with no evidence of recurrence or residual disease on radiographic imaging. Lessons: This unique thymic lesion, featuring LFA-like areas admixed with duct-forming lobulated epithelial proliferation, is best classified as a thymic hamartoma. Review of the literature suggests that previously reported LFAs may also represent hamartomatous lesions rather than true neoplasms. Complete surgical resection appears curative. Further case accumulation and molecular studies are needed to elucidate the pathogenesis.