A case of primary angiomatoid fibrous histiocytoma in the lung

Angiomatoid fibrous histiocytoma (AFH) is a rare mesenchymal tumor of intermediate malignant potential that predominantly affects young adults. The aim of this study was to highlight the clinicopathological features of AFH to assist with establishing a differential diagnosis.

A 28-year-old female was referred to our department for diagnosis and treatment following identification of a 2.5 cm nodule near the hilum of the left upper pulmonary lobe on a computed tomography (CT) scan. She underwent a left upper lobe lobectomy via video-assisted thoracoscopy. On pathologic examination, the lesion measured 2.5 × 2.0 × 0.6 cm with a mitotic count of 0-2/10HPF, tumor necrosis of 0% and marked increased cellularity and spindle cell morphology. The final pathology revealed an AFH. Immunohistochemistry was negative for CK and CD34, focally positive for EMA, CD99, and Desmin, and positive for ALK, CD31, and CD163. Fluorescence in situ hybridization (FISH) and next-generation sequencing analysis were subsequently performed, identifying EWSR1 gene rearrangement. No recurrence or distant metastases were observed during two months of follow-up.

We encountered a rare case of AFH arising from the left upper pulmonary lobe. Its diagnosis required a combination of histopathological examination, immunohistochemistry, and FISH. ALK protein expression is commonly observed in AFH; however, the underlying mechanism remains unclear, as it does not appear to result from ALK rearrangement or amplification.