Bilateral giant progressive massive fibrosis mimicking lung cancer in a rubber factory worker: A rare presentation

Silicosis is typically associated with high-risk industries like mining, making its occurrence in the rubber manufacturing sector exceptionally rare. The advanced form, progressive massive fibrosis (PMF), presents a significant diagnostic challenge as it frequently mimics lung malignancy radiologically and tuberculosis histopathologically.

A 51-year-old female rubber factory worker with a 23-year history of exposure to talc-based anti-adherent powder presented with dyspnea and bilateral upper lobe masses, initially suspected to be lung cancer. Six years prior, she had been misdiagnosed and treated for tuberculosis based on the presence of giant cells in a lung biopsy. In the current admission, contrast-enhanced CT revealed large, non-enhancing masses accompanied by characteristic eggshell calcifications in the mediastinal lymph nodes, suggesting a non-malignant etiology. The definitive diagnosis was established through the integration of pathology and polarized light microscopy. A retrospective review of the previous biopsy reclassified the giant cells from the Langhans type to foreign body giant cells, while polarized light microscopy revealed birefringent polyhedral silica particles dispersed within the fibrous tissue.

This case highlights the diagnostic hazards of overlooking occupational history in low-risk sectors. Progressive massive fibrosis presents a dual diagnostic pitfall by radiologically mimicking malignancy and histopathologically mimicking tuberculosis.