Distinguishing malignant cancerous chest cavity masses from benign ones can be challenging in locations where fungal histoplasmosis infection is prevalent. Chest CT scans enable the identification of mediastinal masses and enlarged lymph nodes, but do not provide a definitive diagnosis.
Researchers from St. Jude Children’s Research Hospital and the University of Tennessee Health Sciences Center in Memphis, TN, are working to develop new criteria to diagnose benign and cancerous chest masses, which they describe in an article published in the August issue of the Journal of Pediatrics.
Histoplasmosis, often called “cave disease”, is a respiratory disease caused by a fungus. Histoplasma capsulatum is found in soil and often is associated with decaying bird and bat feces. Disruption of soil can release infections elements that are inhaled and settle into the lung. The disease is marked by benign involvement of lymph nodes of the trachea and bronchi or by severe progressive generalized involvement of the lymph nodes and tissues rich in macrophages.
The majority of cases of mediastinal masses of pediatric patients living in areas where histoplasmosis is endemic, such as the Ohio and Mississippi River valleys, are benign. However, it is important to make a prompt diagnosis because malignant masses can be rapidly progressive and life threatening, explained principal investigator Elisabeth E. Adderson, M.D. of St. Jude’s department of infectious diseases, and colleagues.
To improve diagnosis and avoid unnecessary surgeries, Dr. Adderson and colleagues analyzed the health records of 131 patients with mediastinal masses who received treatment at St. Jude and Le Bonheur Children’s Hospital in Memphis. The two hospitals provide almost all care for children with mediastinal masses in the region. Review of the electronic medial records revealed that 79% of the masses were benign. Unfortunately, 36% of the patients who had a benign diagnosis also underwent invasive diagnostic testing such as CT-guided or open biopsy to determine this. Patients with malignant masses were diagnosed as having Hodgkin lymphoma, non-Hodgkin lymphoma, and desmoids tumors.
Symptoms included unexplained fevers, night sweats, eight loss, headache, cough, chest pain, neck swelling, and malaise. Laboratory tests included blood tests for the histoplasmosis organism and a lowered white blood cell count.
The review of the CT images showed that the majority of patients had masses limited to a single mediastinal compartment. The authors reported that splenic lesions were observed only in patients with benign disease. The presence of pulmonary nodules, and the absence of an anterior mediastinal mass, pleural effusion, or extrathoracic lymphadenopathy also were significantly associated with benign disease.
Patients who were diagnosed with cancer more often showed anterior mediastinal involvement, extrathoracic lymphadenopathy, and pleural effusion. Abnormal cervical or supraclavicular lymphadenopathy was frequently evident on CT images of patients with cancerous masses.
“Like previous investigators, we found that there was no single clinical, laboratory, or radiologic feature that was good enough by itself to distinguish the masses,” Dr. Anderson said. “But the unique feature that we identified, not previously recognized, was that the presence of lymphopenia and of enlarged cervical lymph nodes on CT scans was more suggestive of a malignant diagnosis.”
New technique to diagnose cancerous chest masses from those caused by fungal infections. Appl Radiol.