Fine Needle Aspiration Received: November 4, 2013 Accepted after revision: January 20, 2014 Published online: March 21, 2014

Acta Cytologica DOI: 10.1159/000358865

Amebic Liver Abscess: Fine Needle Aspiration Diagnosis Maral Mokhtari Perikala Vijayananda Kumar Department of Pathology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

Abstract Objective: To describe the findings in fine needle aspiration (FNA) of an amebic liver abscess (ALA). Study Design: Seven patients (6 men and 1 woman between 52 and 60 years of age) treated for amebic dysentery with multiple liver lesions were selected for ultrasound (US)-guided FNA. The clinical differential diagnosis was malignancy. Abdominal US of the patients revealed multiple, variably sized, well-defined, hypoechoic, cystic liver lesions. FNA of these lesions was performed. Results: Smears of the aspirated material showed necrotic material with mixed inflammatory cells and Entamoeba histolytica trophozoites consisting of round blue bodies with well-defined borders containing a single, eccentrically located nucleus with central karyosome and engulfed red blood cells in the cytoplasm. There were also CharcotLeyden crystals. ALA was diagnosed. Conclusion: FNA can yield the correct diagnosis of ALA and allows early initiation of treatment. ALA should be considered in the differential diagnosis of space-occupying lesions of the liver. © 2014 S. Karger AG, Basel

© 2014 S. Karger AG, Basel 0001–5547/14/0000–0000$39.50/0 E-Mail [email protected] www.karger.com/acy

Introduction

An amebic liver abscess (ALA) is the most frequent extraintestinal manifestation of amebiasis. It is caused by the intestinal pathogen Entamoeba histolytica and colonizes the intestinal tract in about 10% of the population worldwide, but its symptomatic rate is only 10% and about 3–9% of the symptomatic patients develop ALA. The incidence of infection is 3–5 times increased in tropical and developing countries [1, 2] and is not endemic in Iran [3]. The most common mode of infection is from food and water contaminated with feces containing Entamoeba cysts. Other possible routes of transmission are oral and anal sex. Poor sanitation, low socioeconomic status, lack of clean water and densely populated areas are the main risk factors for E. histolytica infestation [4–6]. Other risk factors include homosexuality, HIV infection and immunosuppression [4, 7]. ALA arises from hematogenous spread, mainly via the portal circulation, of E. histolytica trophozoites that gain access to the circulation via invasion of the intestinal wall. Generally, the lesion is solitary and involves the right hepatic lobe, but multiple abscesses in different lobes of the liver have also been reported. Therefore, ALA should be considered in the differential diagnosis of any cystic lesion of the liver, especially in endemic areas [8, 9]. Fine needle aspiration (FNA) is a safe, rapid and costeffective method for the evaluation of liver lesions. AlCorrespondence to: Dr. M. Mokhtari Department of Pathology, School of Medicine Shiraz University of Medical Sciences Zand Street, Shiraz 71345 (Iran) E-Mail Maral_mokhtari @ yahoo.com

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Key Words Amebic liver abscess · Fine needle aspiration · Liver

Color version available online

Color version available online

a

b

Fig. 1. a Liver cyst content shows many inflammatory cells in necrotic background and few Entamoeba trophozoites. b Entamoeba

Fig. 2. Charcot-Leyden crystal. Papanicolaou stain, oil immer-

sion.

trophozoite. Papanicolaou stain, ×400, oil immersion.

Color version available online

though imaging modalities are helpful to diagnose liver abscesses, there is some overlap in the radiological appearance of primary and secondary tumors and liver abscesses because tumors with central necrosis can mimic an abscess. Moreover, differential diagnosis of ALA from a pyogenic abscess is important for appropriate treatment management [10–13]. Our report describes ALA diagnosed based on FNA that was found incidentally on imaging studies and mimicked liver metastasis.

Materials and Methods

Results

FNA was performed by a radiologist under US guidance using a 20-gauge needle. Aspiration yielded good amounts of dark-brown necrotic material. The aspirated material was smeared on glass slides. Half of the slides were air dried and stained with Wright-Giemsa, and half 2

Acta Cytologica DOI: 10.1159/000358865

Fig. 3. E. histolytica trophozoite showing a peripherally located nu-

cleus with central karyosome. Papanicolaou stain, oil immersion.

of them were immediately placed in Carnoy’s solution and stained with Papanicolaou stains. The adequacy of the material was confirmed by the cytopathologist. The smears showed necrotic material with mixed inflammatory cells (neutrophils, lymphocytes, histiocytes and eosinophils) and E. histolytica trophozoites. Trophozoites consist of round, blue bodies with well-defined borders containing a single eccentrically located nucleus with central karyosome and engulfed red blood cells in the cytoplasm. There are also Charcot-Leyden crystal, diamond-shaped, strikingly eosinophilic bodies on Papanicolaou stain (fig. 1–3). Mokhtari/Kumar

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Seven patients (6 men and 1 woman) aged between 52 and 60 years had a history of amebic dysentery that was treated successfully. The time period between dysentery and presentation was 3–5 years. The patients’ clinical presentations were as follows: fever (90%), heaviness and pain over the right upper quadrant of the abdomen (100%) and hepatomegaly (40%). None of the patients had a significant chronic medical illness, immunosuppression or steroid use. Abdominal ultrasound (US) revealed multiple, variably sized, hypoechoic, well-defined, cystic liver lesions. They were selected for US-guided FNA. The proposed clinical differential diagnosis was metastasis. Clinical and radiological data were recorded.

ALA is the most common extraintestinal manifestation of E. histolytica infection. ALA occurs 3–10 times more often in men than in women and is rare in children. The presenting symptoms include fever, cough, dull and constant right upper quadrant pain, hepatomegaly, nausea, vomiting and night sweats. Involvement of the liver surface may lead to diaphragmatic irritation and rightsided chest pain. Peritonitis may occur as a consequence of a ruptured liver abscess [2, 6]. Our ALA cases were clinically suspicious for malignancy. The clinical and radiological presentation of ALA is nonspecific, occurring in various infections (parasitic, tuberculous and pyogenic) and in malignancy [14]. On imaging modalities, ALAs are round to ovoid with irregular wall, and attempts to differentiate this lesion from a pyogenic abscess based solely on radiological findings is a difficult task because the findings are nonspecific. Generally, a pyogenic abscess occurs in younger patients with no sex predilection [6]. The other entity in the differential diagnosis of ALA is a primary or secondary tumor that may show central necrosis and appear cystic by imaging. The presence of an intracystic solid nodule, septations within the lesion, wall thickening and air-fluid level all favor a tumor. However, air-fluid level may be seen in pyogenic abscess due to gas-forming bacteria [10]. In cytologic smears of pyogenic abscesses, inflammation is predominantly neutrophilic, but in ALA the smears are generally neutrophil poor and necrotic, and contain Entamoeba cysts and trophozoites. The most important differential diagnosis of Entamoeba cysts and trophozoites on cytological smears are macrophages. The cytopathologist familiar with morphologic features of the Entamoeba cyst and trophozoites with a high index of suspicion will correctly diagnose ALA. Morphologically, the cysts contain up to 4 nuclei with evenly distributed peripheral chromatin and small centrally located karyosome. Variations in nuclear structure occur: some karyosomes are located eccentrically and peripheral chromatin

References

Amebic Liver Abscess

is irregularly distributed. E. histolytica trophozoites contain 1 nucleus with a chromatin pattern and karyosome similar to the E. histolytica cyst. A characteristic feature of E. histolytica is phagocytosis of erythrocytes [15]. In ambiguous cases, special stains such as periodic acidSchiff and iron may help to spot the amoebae in an inflammatory background [14]. Aspiration of the abscess wall increases the possibility of parasite detection [14]. Because of the immunologic response against E. histolytica, serology has become a valuable adjunct for ALA diagnosis. Various immunological tests are available nowadays with acceptable sensitivity and specificity especially in invasive amebiasis and ALA. These tests are of great help in differentiating ALA from a pyogenic abscess [8]. Although they may be negative in early-phase disease, in cases with high clinical suspicion and negative serology results, reexamination after 7–10 days is advised [8]. A hydatid cyst is another inflammatory cystic liver lesion. Typically, clinical suspicion is a contraindication to performing FNA because of the risk of an anaphylactic shock. FNA will show variable numbers of scolices in an inflammatory background [12, 13]. So, in managing patients with liver lesions, a high index of suspicion for ALA and a history of amebiasis or traveling to endemic areas should be elicited. Management is complicated by the fact that in most ALA cases stool examination is negative for cysts and trophozoites and no concurrent dysentery is present [5]. In conclusion, FNA can yield the correct diagnosis of ALA with exclusion of its mimickers, and allow early initiation of treatment. With better sanitation and treatment, the incidence of amebiasis and its complications decreases, but travels to endemic areas and emergence of immunosuppression (especially AIDS) predisposes patients to this parasitic infection. Acknowledgments The authors would like to thank Dr. Nasrin Shokrpour at the Center for Development of Clinical Research of the Nemazee Hospital for editorial assistance.

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Discussion and Conclusion

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Acta Cytologica DOI: 10.1159/000358865

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Amebic liver abscess: fine needle aspiration diagnosis.

To describe the findings in fine needle aspiration (FNA) of an amebic liver abscess (ALA)...
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