Usefulness of molecular biology performed with formaldehyde-fixed paraffin embedded tissue for the diagnosis of combined pulmonary invasive mucormycosis and aspergillosis in an immunocompromised patient

Abstract

Immunocompromised patients who develop invasive filamentous mycotic infections can be efficiently treated if rapid identification of the causative fungus is obtained. We report a case of fatal necrotic pneumonia caused by combined pulmonary invasive mucormycosis and aspergillosis in a 66 year-old renal transplant recipient. Aspergillus was first identified during the course of the disease by cytological examination and culture (A. fumigatus) of bronchoalveolar fluid. Hyphae of Mucorales (Rhizopus microsporus) were subsequently identified by culture of a tissue specimen taken from the left inferior pulmonary lobe, which was surgically resected two days before the patient died. Histological analysis of the lung parenchyma showed the association of two different filamentous mycoses for which the morphological features were evocative of aspergillosis and mucormycosis. However, the definitive identification of the associative infection was made by polymerase chain reaction (PCR) performed on deparaffinized tissue sections using specific primers for aspergillosis and mucormycosis. This case demonstrates that discrepancies between histological, cytological and mycological analyses can occur in cases of combined mycotic infection. In this regard, it shows that PCR on selected paraffin blocks is a very powerful method for making or confirming the association of different filamentous mycoses and that this method should be made available to pathology laboratories.

Figure 1

A and B: CT scan showing a large excavated pulmonary mass of the pulmonary left inferior lobe, outlined by a glassy feature and associated with pleural effusion (A. Non injected CT scan; B Injected CT scan). C. Mycotic filaments showing the morphological features of aspergillosis isolated from the BAL (Gomori-Grocott silver method × 1000). D. Gross macroscopy of the resected pulmonary lobe showing a hemorrhagic infarct.

Figure 2

A. Hyphae with a large diameter invading blood vessels (HES, original magnification, × 400). B. Morphological features of mucorales (Gomori-Grocott silver method, original magnification × 1000). C. Association of two different hyphae in the same tissue section showing morphological feature of mucorales (arrowhead) and of aspergillosis (arrow). Asteriks: associated bacteria (HES, original magnification, × 800). D. Molecular biology a: PCR of Aspergillus b: PCR of Mucor: M: Marker, neg: negative controls, pos: positive controls.

Figure 3

A. Stereomicroscopic image of the habit sketch of Rhizopus microsporus var rhizopodiformis. B. Micromorphology showing the dark brown unbranched sporangiophores born directly from rhizoids. C. Finely roughened (sub) spherical sporangiospores