Rare case of echinococcosis with negative histology and cytology

Clinical History

A 25-year old male patient from Syria had a long hospitalisation due to fever and haemoptysis with unknown aetiology, chest pain and dyspnoea.

Imaging Findings

The contrast-enhanced CT of the lungs and upper abdomen showed a cystic lesion in the upper lobe of the left lung with fluid and air bubbles. It also showed atelectasis and pleural fluid in the left hemithorax and mediastinal shift to the right (Figs. 1 and 2). In the axial plane the CT showed a waterlily-sign (Fig. 3); a detachment of the endocyst membrane which results in floating membranes within the pericyst; a classic appearance of echinococcosis cyst.
Serological tests for hydatidosis were not significantly elevated.
Histology and cytology samples with ultrasound-guided core-needles from different areas of the cyst (and later ELISA-test) were taken and had negative results, thus a diagnosis of the patient could not be given. The patient therefore underwent a long series of tests (TB, staphylococcus etc.) without positive findings. Due to the patient’s condition getting worse he underwent surgery and the pathology exposed an echinococcal cyst.

Discussion

Human echinococcosis (HE) is a rare condition caused by the larval stage of the tapeworm from the genus Echinococcus. There are two species of echinococcus; The E. granulosus which causes cystic echinococcosis or hydatidosis and E. multilocularis which causes alveolar echinococcosis [1].
The typical life cycle of echinococcus starts as the adult worms reside in the intestine of a main host such as wolves, foxes and dogs. The released eggs are then ingested by intermediate hosts such as goats, sheep and horses where they hatch in the small intestine. Here, the larvae penetrate through the gut wall and follow the bloodstream. Eggs are also released into the environment where they can survive for at least one year [2].
Transmission to humans happens faecal-orally. Predisposing factors such as pets, drinking water and spoiled food can cause transmission to humans which spreads to the bloodstream and the organs. This way, humans can develop life-threatening illnesses. However, the parasite is not contagious from one human to another [1].
Echinococcus are most commonly found in the liver (55-70%) and in the lungs (18-35%) [3].
The symptoms can vary and depend on the location of the cyst, hence it can mimic many conditions but usually pain and fever are present [2].
HE is a major zoonotic disease and is globally a major burden both financially and in terms of public health. The disease is emerging in Europe but it is unclear if the parasite range is spreading or the surveillance has led to greater detection rates [4].

X-rays are the most used examination in echinococcosis of the lung. CT and MRI are nevertheless better at diagnosing HE due to a better recognition of certain details, lesions and surrounding structures [5].
Diagnosis of HE has the highest sensitivity and specificity when using ultrasound-guided core-needle biopsies; cystology (ELISA) with a sensitivity of 96, 5% and histology with a sensitivity of 100% [6,7].
However, needle aspiration and biopsy from the cyst is a controversial issue due to the risks of allergic reactions and anaphylaxis [8].
Treatment is primarily chemotherapy or/and surgery depending on different criteria.
Prognosis is satisfactory if treated surgically. Most complications include pleural infections and prolonged air leakage. Operative mortality is between 1-2 % [9].

In our case it was surprising that neither cytology nor histology from different areas of the cyst showed echinococcus whereas CT was classic for the disease.

Written informed patient consent for publication has been obtained.

Differential Diagnosis List

Final Diagnosis

Echinococcosis.

URL:	https://www.eurorad.org/case/14071
DOI:	10.1594/EURORAD/CASE.14071
ISSN:	1563-4086