Correct!
2. Fibrosing mediastinitis
All the disorders listed as choices can be associated with hypermetabolic masses in the mediastinum (1). Metastatic cancer is usually unilateral and rapidly progressive. Metastatic disease, Hodgkin’s disease or lymphoma would be expected to rapidly progress and not have the slow progression observed in our present patient. Clinical and radiologic features of fibrosing mediastinitis and selected diffuse mediastinal diseases are shown in Table 1.
Table 1. Fibrosing mediastinitis and differential diagnoses of non-neoplastic diffuse mediastinal diseases (1).
The present patient’s disease is consistent with fibrosing mediastinitis which is the most likely diagnosis. Fibrosing mediastinitis, also known as sclerosing mediastinitis, is a condition related to an abnormal immunologic reaction that results in the proliferation of fibro-inflammatory tissue in the mediastinum and/or hila. It leads to a variable constriction of systemic veins, pulmonary arteries and veins, the airways and/or the esophagus, with a morbidity related to location and extent of fibrosis. The pleura, pericardium, and coronary arteries may also be involved. The most common form of fibrosing mediastinitis is the focal or granulomatous subtype of fibrosing mediastinitis, mainly due to histoplasmosis (less frequently tuberculosis), and other fungal or inflammatory conditions. This form usually manifests as a localized, calcified mass in the paratracheal or subcarinal regions of the mediastinum or in the pulmonary hila, commonly responsible for a superior vena cava syndrome. Diagnosis can be made based on imaging findings, preventing the need for tissue sampling.
There is also a diffuse or non-granulomatous subtype of fibrosing mediastinitis which accounts for about 10 to 20% of cases. It may be idiopathic or can originate in association with autoimmune disorders, methysergide exposure, or prior radiation exposure. Fibrosing mediastinitis has been reported as an unusual mediastinal manifestation of IgG4-related disease. The diagnosis requires a comprehensive evaluation for other disease manifestations, including Riedel’s thyroiditis, retroperitoneal fibrosis, sclerosing cholangitis, or autoimmune pancreatitis, which may precede and/or suggest the diagnosis.
In addition to IgG4 disease, some disorders, such as Erdheim-Chester disease, must be suspected in case of multisystemic involvement. This rare, non-inherited, non-Langerhans form of histiocytosis, commonly with a BRAF mutation, is characterized by xanthomatous infiltration of the involved tissues with foamy histiocytes surrounded by fibrosis, and appears with heterogeneous systemic manifestations.
Castleman’s disease is a very rare heterogeneous cluster of disorders, with distinct unicentric and multicentric subtypes. Subsequently, the fundamental roles of human herpesvirus-8 (HHV-8) and interleukin-6 (IL-6) has been identified in a significant proportion of cases.
Which of the following medications has been reported to result in dramatic improvement in patients with fibrosing mediastinitis? (Click on the correct answer to be directed to the 6th and final of 7 pages)