15-Flourine-flourodeoxyglucose ( FDG ) is not sensitive for cancer cells . 4 False positive results are seen in cases of active infection or inflammation , highlighting the importance of good clinical correlations between patient symptoms and imaging findings . As illustrated in our case presentation , the patient ’ s PET was certainly positive ; however , her nodule was inflammatory in nature as opposed to malignant .
Histoplasmosis is an endemic mycotic infection native to North America . It is reported that 60-90 % of people who live in the Ohio and Mississippi river valley regions in the US are thought to have been exposed at some point in their lifetime . 6 Current epidemiologic data indicate that the area of endemicity for histoplasmosis is much larger and includes areas beyond the Ohio and Mississippi river valleys . 7 Histoplasma spp . is a dimorphic budding yeast that is introduced to the pulmonary system by inhalation ; it may then spread via the lymphatics or blood to other organ systems . There are many presentations of histoplasmosis , ranging from asymptomatic to fulminant dissemination . There can be multiple associated conditions such as fibrosing mediastinitis , mediastinal granulomas , erythema nodosum , histoplasmosis associated pericarditis , and others . 8 Pulmonary symptoms are the most common , and imaging in symptomatic pulmonary histoplasmosis may demonstrate hilar and mediastinal adenopathy but may also demonstrate focal infiltrates . In patients with underlying structural lung disease , cavitation can occur . The actual time course for imaging resolution has not been defined , but it can take years before granulomatous nodules calcify . 8 , 9 Pulmonary histoplasmosis can have an acute and chronic form . The acute form is characterized by a spectrum of no symptoms to a flu-like illness to severe illness in immunocompromised hosts . Chronic disease may present with cavitary lesions . 9 , 10 , 11 Less than 1 % of total cases manifest as chronic pulmonary histoplasmosis or with granulomatous lesions . 8 Patients who are immunosuppressed or those who receive a heavy inoculum or longer duration of exposure are typically those who develop more severe diseases . Only about 5 % of those who are exposed to the organism will develop symptoms . 9
PET-CT image showing the mild hypermetabolic activity ( 5.7 SUV ) of the left lower lobe pulmonary nodule seen in Figure 1 .
Pathological image showing the benign granuloma in the resected tissue .
Pneumothorax is not recognized to occur in acute histoplasmosis . However , calcified Histoplasma nodules in chronic histoplasmosis are known to have the potential to erode bronchi , become a broncholith ,
FIGURE 2
FIGURE 3
and subsequently cause hemoptysis . 9 Other nodular conditions , such as rheumatoid arthritis and mycotic infections , have been known to cause pneumothoraxes . Pneumothorax has also been documented
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