Deep Benign Fibrous Histiocytoma of the Anterior Mediastinum Mimicking Malignancy

The following report describes the case of a 43-year-old male smoker that was referred to the rapid access lung clinic with haemoptysis, chest pain, and axillary lymphadenopathy—a clinical picture that raised concern for a possible underlying malignancy. Preliminary investigations revealed elevated D-dimers, low-volume haemoptysis, and a normal chest X-ray, which lowered the index of suspicion. However, computed tomography (CT) pulmonary angiogram identified a right hilar mass, several parenchymal cysts, and a large mediastinal mass. In addition, a left-sided adrenal lesion was also discovered following CT abdomen pelvis, potentially indicating metastatic disease. Fortunately, a positron emission tomography scan failed to detect any metabolic activity in either the right hilar mass, left adrenal lesion or the anterior mediastinal mass. CT-guided biopsy identified the mediastinal mass as a low-grade spindle cell tumour. Due to its large size, the mass was surgically resected and confirmed to be a deep benign fibrous histiocytoma. The significance of this report is to highlight a clinical presentation suggestive of malignancy but actually resulting from a rare variant of a benign tumour. The constellation of regional lymphadenopathy, respiratory and gastrointestinal symptoms, lung cysts, an adrenal tumour, and a mediastinal mass appeared to suggest a progressive disease pattern more commonly associated with malignancy.