INTRODUCTION: Intrathoracic lymphadenopathy can be a manifestation of malignancy, infectious or immunologic conditions. In endemic zones, clinicians are frequently faced with the situations of bulky intrathoracic lymphadenopathy and lung lesions. It then becomes challenging to differentiate the infectious lesions from malignant ones. If bronchoscopy is negative, usually next step in diagnosis is surgical biopsy. With the introduction of FDG PET (Fluorodeoxyglucose Positron emission tomography) scan, followed up with dual-time imaging, invasive diagnostic procedure could be avoided. We report a case where we were able to avoid surgery in a young female with intrathoracic lymphadenopathy.
CASE PRESENTATION: A 38 year old asymptomatic, nonsmoker female was found to have a right hilar mass on a routine chest x-ray. This was confirmed by CT scan of the chest which showed right hilar mass of 3.8 x 3cm. Physical examination was normal. A bronchoscopy showed no endobronchial lesion; broncho-alveolar lavage (BAL), transbronchial biopsy (TBB) and transbronchial needle aspiration (TBNA) were done, which were negative for malignancy and infections. Patient came for follow-up after five months with repeat CT scan of chest. It showed increase in size of the right hilar mass (from 3.8 x 3cm, to 4.2 x 3.2cm) along with new findings of subcarinal lymph node enlargement (2.3cm). Repeat bronchoscopy with BAL, TBB and TBNA were performed. The results were again negative for malignancy or infectious causes. A PET scan was done which showed intensely avid subcarinal lymph node and right hilar node, with drop in Standardized uptake value (SUV) on delayed scan. The right hilar node had SUV max of 4.3 on initial imaging which dropped to 3.8 on delayed imaging at one hour. Similarly, the subcarinal node had SUV max initially of 8.4 which dropped to 8.0 on delayed imaging. The patient was young, asymptomatic, nonsmoker, from histoplasma endemic zone, and had negative bronchoscopy twice. Additionally, with the PET scan findings, the lesion was presumed to be due to histoplasmosis and treatment was initiated with itraconazole and prednisone orally. Repeat PET scan done four months later showed decreased in size of the right hilar mass and subcarinal lymph node as well as decrease in SUV max in these lesions.
DISCUSSION: Histoplasma Capsulatum; causative agent for Histoplasmosis is an endemic fungi in Ohio Mississippi river valley area. Pulmonary manifestations including intrathoracic lymphadenopathy and lung lesions are common presentations of histoplasmosis. Objective diagnosis of these lesions is usually challenging, due mainly to low organism load in clinical specimens. Bronchoscopy with TBB & TBNA is frequently non-diagnostic. Similarly, cultures and antigen tests are also negative most of the time. Usually these patients are sent for surgical biopsy for confirmatory diagnosis. Currently FDG- PET scan is being used increasingly for staging of malignant diseases, and to differentiate benign from malignant lesions. In SPNs (solitary pulmonary nodules), usually a higher SUV (usually more than 2.5) is believed to suggest malignant lesions (1). However, several benign conditions, such as Sarcoidosis, Tuberculosis, Histoplasmosis, has been reported to have higher SUV. In these cases where lesions have higher SUV value, DTP (Dual time PET) scan has shown some promise to differentiate between the malignant and benign lesions. A lesion is likely to be malignant if the SUV uptake increases on DTP, whereas it is likely to be benign if the SUV is stable or decreases(1,2). In our case, although the initial SUV of the lesions were high, they decreased in delayed scan suggestive of non-malignant nature of the lesions.
CONCLUSIONS: In patients from endemic area for histoplasmosis presenting with intrathoracic lymphadenopathy and lung lesion, DTP scan can be helpful in avoiding surgical biopsy for diagnosis.
Reference #1 Schillaci O, Travascio L, Bolacchi F et al. Accuracy of early and delayed FDG PET-CT and of contrast-enhanced CT in the evaluation of lung nodules: a preliminary study on 30 patients. . Radiol Med. 2009 Sep;114(6):890-906. Epub 2009 Jul 4
Reference #2 Núñez R, Kalapparambath A, Varela J. Improvement in sensitivity with delayed imaging of pulmonary lesions with FDG-PET. Rev Esp Med Nucl. 2007 Jul-Aug;26(4):196-207
DISCLOSURE: The following authors have nothing to disclose: Dipen Kadaria, Nicole Pant, Muthiah Muthiah, Muhammad Zaman
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