Unusual aspect of cuticular morphology in human pulmonary dirofilariasis.
This case illustrates the importance of molecular analysis in accurately diagnosing pulmonary dirofilariasis when histopathological features are ambiguous.
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A 79-year-old woman underwent partial lung resection due to a pulmonary nodule, which was found to contain fragments of a filarial worm. Histopathological examination indicated features consistent with Dirofilaria immitis, while molecular analysis confirmed the species. This case emphasizes the diagnostic challenges in identifying pulmonary dirofilariasis based solely on morphology.
Abstract
A 79-year-old woman was found to have a slowly enlarging pulmonary nodule in the right upper lobe, and partial lung resection was performed for diagnostic and therapeutic purposes. Histopathological examination revealed fragments of a filarial worm within the nodule. The parasite showed features compatible with Dirofilaria immitis, including a thick multilayered cuticle, abundant somatic musculature, and prominent internal longitudinal ridges projecting into the lateral cords. However, the external cuticular surface showed localized ridge-like elevations, making distinction from Dirofilaria ursi difficult on morphology alone. A partial sequence of the mitochondrial 12S rRNA gene was amplified from formalin-fixed, paraffin-embedded tissue and analyzed phylogenetically. The sequence clustered within the D. immitis clade and was clearly separated from D. ursi and Dirofilaria repens. This case highlights a diagnostic problem in tissue-based identification of pulmonary dirofilariasis and demonstrates the value of molecular analysis when histopathological morphology is ambiguous.