[Pathological diagnosis and ultrastructure features of primary pulmonary cryptococcosis: a study of 27 cases]

To investigate diagnostic histopathology and ultrastructure features of primary pulmonary cryptococcosis (PC).

Clinical data and pathologic findings of 27 cases of PC were retrospectively reviewed, light and electron microscopic evaluations and histochemistry stain studies were performed.

The specimens consisted of 2 fine-needle aspiration lung biopsies and 25 cases of open lung biopsies. Cryptococcosis granuloma formation was identifiable by histopathological examination in 25 of 27 cases, with gum-like lesion and fungi in the remaining 2 cases. The detection rates of cryptococcus neoformans (CN) by mucicarmine (MC), periodic acid-Schiff (PAS), alcian blue (AB) and Grocott methenamine-silver (GMS) were 87.0% (20/23), 100% (27/27), 66.7% (18/27), and 100% (23/23) respectively. Under the electron microscope, most CN had a simple structure with a few organelles. The capsule was seen in all organisms. A percentage of the organisms showed nuclei, nucleoli, mitochondria and vacuoles. The detection rate of CN by EM was 91.7% (11/12).

The clinical manifestation and imaging of PC are nonspecific for PC. Lung biopsy is the major diagnostic modality. The detection rate by electron microscopy was quite high. Therefore, a correct diagnosis of pulmonary cyrptococcosis should rely on the combination of histopathological evaluation, histochemistry staining and/or electron microscopic examination.