PMC8044558_01
A smoothly delineated cystic tumour with a maximal diameter of 9 cm is visualised in the lower lobe of the left lung in a chest radiograph (a) and in computed tomography scans ((b) and (c), asterisks). Note the attenuation of contrast media in the periphery of the lesion ((c), arrow). The adjacent lung parenchyma appears inconspicious.
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A chest radiograph (Figure 1(a)) and a subsequent contrast-enhanced computed tomography scan (Figure 1(b) and (c)) revealed a smoothly delineated cystic tumour with a maximal diameter of 9 cm in the lower lobe of the left lung with attenuation of contrast media in the periphery of the lesion, whereas the remainder lung parenchyma appeared inconspicuous.
Surgical resection specimen of the lower lobe of the left lung with a cystic lesion ((a), asterisk). Histomorphologically, a hydatid cyst shows an outermost layer (pericyst or ectocyst, respectively) consisting of granulation tissue and fibrosis and multinucleated giant cells (asterisk). Adjacent to the pericyst is a laminated membrane or exocyst (arrowhead). The innermost layer is termed the germinative layer or endocyst, which is actively producing both laminated membrane outward and brood capsules and protoscoleces inward (arrow) (b). Close-up of the germinative layer with brood capsules containing protoscoleces (c). During work-up for frozen section examination, a smear cytology was performed, which facilitates the diagnosis by identification of brood capsules containing protoscoleces. This smear preparation was later stained according to Papanicolau (d).
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Macroscopically, the resected lobe showed a cystic lesion with a whitish fibrous rim containing turbid fluid (Figure 2(a)). Histomorphologically, the periphery of the cystic lesion showed a thick fibrous rim, consisting of an outer acellular laminated membrane and a germinal membrane with nucleated lining with numerous protoscolices with occasional hooklets (Figure 2(b) and (c)). Some of the smears were later stained according to Papanicolau (Figure 2(d)).