PHG is a very rare fibrotic nodular disease whose aetiology remains unknown. It is related to an abnormal immune response and can be associated with extrapulmonary fibrotic conditions like sclerosing mediastinitis, retroperitoneal fibrosis or Riedel’s thyroiditis [1, 2, 3]. Our case was associated with a perihepatic mass (the other 2 intrahepatic hypodense lesions have not yet been characterized).
Most patients are asymptomatic and the disease is usually diagnosed as an incidental finding trough an image test. However, some individuals may suffer non-specific symptoms like cough, fever, fatigue or dyspnoea [1, 2, 3].
Chest radiographs show multiple (70%) or solitary (30%) nodules with well-defined borders, diameter ranging from 0.2 to 15cm (mean 2cm), bilateral and randomly distributed. Calcification and cavitation are not common. Nodules often remain stable for long periods, but they can grow slowly. Lymphadenopathies are not observed in this entity [1, 2, 3].
When these findings are present you should rule out a malignant metastatic disease or a primary (lung or lymphoma) tumour. Other possibilities are infection (tuberculosis, septic emboli or fungal infections), sarcoidosis, amyloidosis, silicosis, rheumatoid nodules, Wegener's granulomatosis, lymphomatoid granulomatosis, and plasma cell granuloma [1, 2, 3].
Final diagnosis is made by histopathological examination. Microscopically, a hypocellular network of concentric hyalinised collagen surrounded by a lymphocytic infiltrate is presented [1, 2, 3]. Macroscopically, whitish and well-defined nodules similar to a cotton-ball are characteristics [3].
This entity has a good prognosis. Nowadays, malignant degeneration has not been described. Treatment consists in resection and watchful waiting for solitary lesions or corticosteroid drugs in cases of multiple lesions [1, 2, 3].
In conclusion, PHG is a rare benign disease that can mimic a metastatic lung cancer. Biopsy is necessary for the diagnosis.