Category: Technical Articles
||Histoplasmosis is a common fungi (yeast) which can infect the lungs and sometimes spread to other parts of the body (disseminated histoplasmosis). Histoplasmosis infections can range for mild and asymptomatic to moderate (with cough, fever, and flu symptoms) to fatal infections.
Aline Gehlen Dall Bello et al. Histoplasmosis mimicking primary lung cancer or pulmonary metastases. J Bras Pneumol 2013;39:63-8. AND
Khaled Salhab et al. Growing PET positive nodule in a patient with histoplasmosis: case report. Journal of Cardiovascular Surgery 2006;1:23. AND
Sandra Starnes et al. Can lung cancer screening by computed tomography be effective in areas with endemic histoplasmosis? Journal of Thoracic and Cardiovascular Surgery 2011;141:688-93.
Histoplasmosis can often prove fatal in immunocompromised patients such as HIV patients. Histoplasmosis spores are especially common in the droppings of birds and bats. In the USA, Histoplasmosis infections are especially common in the USA in the Ohio and Mississippi River valleys.
Histoplasmosis can also produce lung nodules which resemble primary or metastatic lung cancer. A Brazilian study of 294 histoplasmosis patients reported that 15 (5.1%) had chest CT (computed tomography) scans which mimicked lung cancer. A case was presented of a 64 year old New York state fisherman whose CT and PET (Positron Emission Tomography) chest scans indicated lung cancer. The patient underwent left lower lobectomy (removal of the lower left lung). Pathology of the lower left lung indicated that the patient had histoplasmosis infection but not lung cancer.
Other research has documented that lung infections with Aspergillus and other molds can also resemble lung cancer on CT scans and other lung imaging techniques. Other factors which can cause false-positive CT lung scans which appear to be lung cancer include: 1) infections with TB and other bacteria, 2) exposure to toxic and/or allergenic substances such as asbestos, 3) pulmonary fibrosis, and 4) autoimmune diseases like sarcoidosis.
Several published studies have examined the efficacy of chest CT screening for those at high risk for lung cancer (such as tobacco smokers, persons with respiratory problems, or a family history of lung cancer). Some studies have reported that the use of CT scans are associated with significantly lower lung cancer death rates by detecting lung cancer in its earlier and more treatable stages. Other studies have reported that screening CT chest scans are not associated with any significant change in lung cancer death rates. However, on the negative side, it is estimated that only 13 to 20% of positive nodules on chest CTs are actually lung cancer. Such a 80 to 87% “false negative” rate of CT scans can cause unnecessary surgery and other invasive procedures, increased risk of infections and other adverse events, and cause a great deal of worry among patients and their families. More research is needed to improve lung cancer screening techniques to catch as many lung cancer cases as possible (ie. improve the sensitivity of testing) while avoiding as many false-positive cases as possible (ie. improve the specificity of testing).