Utility of percutaneous lung biopsy for diagnosing filamentous fungal infections in hematologic malignancies

The incidence of invasive filamentous fungal infections in hematologic patients is increasing as a consequence of high dose chemotherapy and bone marrow transplant procedures. Mortality is usually very high. The diagnosis is often difficult and yet a fast, accurate diagnosis is of fundamental importance for treating the infection and planning subsequent management of the hematologic disease. We evaluated the sensitivity of computed tomography (CT)-guided percutaneous biopsy in diagnosing pulmonary fungal infections.

Between 1997 and 2002 we performed 17 CT-guided percutaneous transthoracic lung biopsies in 17 hematologic patients with suspected filamentous fungi infection with negative BAL, to obtain a certain diagnosis and to know what species of fungi was responsible for infection. In all cases suspected mycosis began during the post-chemotherapy aplastic period. Patients were receiving antifungal therapy at the time of all biopsies. When the platelet count rose above 50 x 10(9)/L, CT-guided percutaneous lung biopsy with fine-needle aspiration for cytology was performed.

Twelve of 17 patients had histologic confirmation of the fungal infection (70.5%), 8 with Aspergillus spp. 4 with Mucorales spp. Biopsies provided non-specific results in 4 cases; in 2 of these cases, clinical course and response to therapy confirmed the diagnosis of mycosis; in the last case bronchoalveolar carcinoma was found as a new diagnosis. Cultures were positive in only 6 cases, all for Aspergillus spp. The sensitivity of CT-guided percutaneous lung biopsy was 70.6% and its positive predictive value (PPV) was 100%. This procedure provided an immediate diagnosis and only one side-effect (1 pneumothorax, without complications).

Histologic discrimination between aspergillosis and mucormycosis is very important for deciding secondary prophylaxis during transplant procedures, because Mucor is usually resistant to azoles.