Fine needle aspiration biopsy of liver – an update

May 12, 2004

http://www.wjso.com/content/2/1/5

12-May-2004

Review

Fine needle aspiration biopsy of liver – an update

C Chhieng

Department of Pathology, University of Alabama at Birmingham, Birmingham,

AL, United States of America

World Journal of Surgical Oncology 2004, 2:5

The electronic version of this article is the complete one and can be found

online at: http://www.wjso.com/content/2/1/5

Received 25 February 2004

Accepted 16 March 2004

Published 16 March 2004

verbatim copying and redistribution of this article are permitted in all

media for any purpose, provided this notice is preserved along with the

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Because appropriate clinical management is guided by the nature of the mass,

accurate diagnosis of discrete hepatic masses is very important. Possible

treatments range from supportive care for advanced metastatic lesions to

partial hepatectomy for primary carcinomas. Despite recent improvement,

radiological imaging does not always allow precise characterization of the

lesions. Serological markers (such as alpha fetoprotein) can be useful in

narrowing the differential diagnosis when they are markedly elevated but a

substantial number of patients unfortunately do not have high levels of

these markers at the time of presentation. Therefore, a tissue diagnosis is

often required to guide subsequent management. Fine needle aspiration biopsy

(FNA) under image guidance has gained increasing acceptance as the

diagnostic procedure of choice for patients with focal hepatic lesions. It

can be performed percutaneously or endoscopically. This review will discuss

fine needle aspiration biopsy of liver from a pathologist's perspective. The

review will also address the cytology and the pitfalls of some of the more

commonly encountered hepatic lesions as well as those that may pose

diagnostic challenges.

Currently, there are several diagnostic procedures to obtain preoperative

tissue diagnosis to guide subsequent therapy. They include image guided fine

needle aspiration biopsy, blind percutaneous needle core biopsy, and

transjugular needle core biopsy. Percutaneous needle core biopsy without

imaging guidance is excellent for diagnosing diffuse liver diseases such as

hepatitis, cirrhosis, and metabolic diseases. Accuracy is superb and the

complication rate is low. However, it is not indicated for focal, discrete

hepatic lesions. To minimize the risk of hemorrhage, transjugular approach

is often reserved for patients with a bleeding diathesis. Fine needle

aspiration biopsy (FNA) under image guidance has gained increasing

acceptance as the diagnostic procedure of choice for patients with focal

hepatic lesions. It can be performed percutaneously or endoscopically. The

latter approach is technically difficult for lesions located far away from

the tip of the echoenodoscope and lesion near the 2nd or 3rd portion of the

duodenum because of poor visualization [1]. FNA may also be performed at

laparoscopy or laparotomy under direct vision when imaged guided FNA fails

to provide diagnostic tissue [2].

This review is not intended to be exhaustive. Therefore, the discussion is

limited to the lesions that are more commonly encountered in day-to-day

practice and those that may pose diagnostic challenges.

Operating characteristics of FNA

In experienced hands, FNA is safe, minimally invasive, accurate, and cost

effective. The specificity of FNA biopsy of the liver approaches 100% and

the sensitivity ranges from 67–100%, averaging about 85% [3-9]. FNA alone is

superior to core biopsy alone because the needle is longer, can be guided,

and the procedure can be easily repeated [10,11]. However, both methods are

complimentary to each other [10,12,13].

Complications of FNA

The occurrence of complications after hepatic FNA is rare with about 0.5%

minor complications, 0.05% major complications requiring surgery, and less

than 0.01% mortality [14-17]. They are limited largely to hemorrhage. The

frequency of complications is often related to the vascularity and the

location of the lesions as well as the needle size [18]. Another concern is

the subcutaneous seeding of tumor along the needle tract during precutaneous

liver FNA. The incidence varies with the diameter of the needle, the number

of passes, and the amount of normal parenchyma around the lesion to be

traversed by the needle [7]. It is still an extremely rare complication. For

example, there are only a few case reports of needle tract seeding when

using needle of 23 gauge or less [19-21].

Contraindications of FNA

Absolute contraindications for FNA of liver include uncorrectable bleeding

diathesis, a lack of a safe access route e.g. vascular structure in the

biopsy path, and uncooperative patients.

Specimen preparation

It is crucial to handle the aspirate quickly and optimally in order to

minimize artifacts. Ideally, both direct smears and cell block should be

prepared for all FNA of livers. Cell block preparation is especially useful

if immunohistochemical study is required for differential diagnosis. Direct

smears are made by spreading a small volume of aspirated material on

prelabeled slides which can be either air-dried or fixed in 95% ethanol. The

air-dried smears are stained with a modified Giemsa stain. The alcohol-fixed

smears are stained with the Papanicolaou method. A cell block is then

prepared from residual materials rinsed from the needle.

Several studies have shown that the assistance of cytopathologists during

the procedure increases overall accuracy [22-24]. The latter is attributed

to the ability to assess specimen adequacy at the time of biopsy and to

determine if additional tissue is required for diagnosis and/or ancillary

studies such as flow cytometry.

Although clinical and/or radiological findings cannot reliably distinguish a

primary hepatic malignancy from a metastatic disease, they can help to

narrow the differential diagnosis. The age of the patient may suggest

certain processes. For example, metastatic disease and primary

hepatocellular carcinoma (HCC) more frequently affect older patients whereas

benign lesions such as liver cell adenoma and fibrolamellar variant of HCC

tend to occur in younger patients. Hepatoblastoma occurs primarily in

infants [25]. Patients with liver cell adenoma often have a history of long

term steroid use.

Another informative clue is the presence or absence of cirrhosis. For

patients with cirrhosis, HCC is a more likely finding in the United States

[26]. However, 10–20% of nonfibrolamellar HCCs occur in patients without

cirrhosis. Fibrolamellar HCC always occurs in noncirrhotic liver.

A markedly elevated serum AFP level, >1,000 ng/ml, is highly suggestive of

HCC or in children, hepatoblastoma. A moderate increase in serum AFP,

however, is non-specific and can be seen in a wide variety of benign and

malignant conditions. Patients with fibrolamellar variant of HCC may not

demonstrate an elevated serum AFP level.

The finding of a single, large mass with or without smaller satellite

lesions on imaging is more typical of a HCC whereas metastatic lesions often

present with multiple lesions of similar size.

Figures

Figure 1

Focal nodular hyperplasia

Figure 2

Hepatocellular carcinoma

Figure 3

Hepatocellular carcinoma

Figure 4

Cholangiocarcinoma

Figure 5

Hemangioma

Tables

Table 1

Cytology of normal hepatocytes and bile duct epithelium.

Aspirates of normal liver consist predominantly of hepatocytes and scattered

bile duct epithelial cells. Table 1 summarizes the cytologic features of

these two types of cells. Other cell types such as endothelial cells and

Kupffer's cells are infrequently noted. Occasionally, mesothelial cells and

small bowel mucosa may be inadvertently sampled depending on the approach.

They should not be mistaken for tumors.

Cirrhosis may be sampled by FNA when a dominant nodule mimics a HCC

radiologically. The cytology of cirrhotic liver is similar to that of normal

liver. Occasionally, markedly reactive hepatocytes may display significant

cytological atypia including variable nuclear size, increase

nuclear/cytoplasmic ratio, coarse chromatin, prominent nucleoli, and

frequent bi- or multinucleation. In some instances, they may represent a

dysplastic process. Separating a " dysplastic " nodule and HCC in a cirrhotic

liver based on cytology alone can be difficult, if not impossible, since

their distinction is often based on architectural criteria [27,28]. For this

reason, this constitutes a potential source of false positive error [29].

Focal nodular hyperplasia and liver cell adenoma

Both focal nodular hyperplasia (FNH) and liver cell adenoma usually affect

patients in their 3rd and 4th decades with a female predominance [26]. The

serum AFP level and liver function test are often within normal ranges.

Focal nodular hyperplasia is usually asymptomatic and is sometimes

characterized by the presence of a central area of low attenuation

radiologically [30,31]. Patients with liver cell adenoma may present with an

acute abdomen and may be associated with a history of steroid use [32,33].

Cytologically, both lesions are composed of bland appearing hepatocytes

(Figure 1). For FNH, bile duct epithelium and stromal fragments may be

present. Aspirates of liver cell adenoma characteristically contain

hepatocytes only; however, evidence of hemorrhage and necrosis may be noted

[34,35]. In making a diagnosis of these entities, it is crucial that the

needles are within the lesion and only the lesions are sampled.

Hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary hepatic malignancy

[26]. The cytological appearance of HCC varies with the degree of

differentiation. The diagnosis of moderately differentiated hepatocellular

carcinomas is usually straightforward because they look like normal liver

while at the same time demonstrating obvious malignant features. At one end

of the spectrum, the tumor is well differentiated – it resembles liver but

does not look obviously malignant. On the opposite end of the spectrum, the

tumor is poorly differentiated – it is obviously malignant but may be

difficult to appreciate its hepatic origin.

Differentiation between well differentiated hepatocellular carcinoma and

benign hepatic lesions

One very helpful diagnostic clue for well differentiated HCC is the presence

of one of the two characteristic endothelial patterns. The first one is

basketing – endothelial cells wrap around groups or trabeculae of

hepatocytes (Figure 2). This pattern is observed in 50% of HCC but is

specific for HCC [36-39]. The pattern is seldom seen in benign hepatic

lesions or other malignancies. The other endothelial pattern consists of

traversing capillaries through groups of hepatocytes (Figure 3). This

pattern is noted in over 90% of HCC but is less specific than the

" basketing " pattern since it can be seen in other malignancies and rarely,

some non-neoplastic liver conditions [38]. Other features that favor a well

differentiated HCC over benign hepatic lesions include acinar formation and

the presence of prominent " cherry red " nucleoli.

Ancillary studies may be helpful in differentiating benign and neoplastic

hepatocytes. Decrease or absent reticulin staining or positive staining

pattern outlining trabeculae greater than three cells thickness support the

diagnosis of HCC [40,41]. Others have shown that the presence of diffuse

immunostaining with CD34 and Factor VIII also favor HCC [41,42]. Positive

AFP staining is reported in 40% of HCC, but negative staining does not rule

out a diagnosis of HCC [43]. DNA ploidy and staining for proliferating cell

nuclear antigen (PCNA) have shown some promises, but there is substantial

overlap in the patterns of benign and neoplastic processes [44-46].

Differentiation between poorly differentiated hepatocellular carcinoma and

metastatic adenocarcinoma

In many instances, a known history of primary tumor is available and the

task is to determine whether the morphology of the liver lesion is

compatible with that of the known primary tumor. However, when a history is

not available, the questions that need to be addressed will be " Is it

primary? " or " Is it metastatic? " A markedly elevated serum AFP level and the

finding of a single lesion with or without satellite lesions on imaging

favor a primary tumor over metastatic disease.

Cytologically, bile production, as evidenced by the presence of bile in the

cytoplasm of malignant cells or in canaliculi between malignant cells, is

considered diagnostic of HCC. Unfortunately bile is present in only half of

the cases [37,39,47]. Although the " basketing " endothelial pattern is

pathognomonic for HCC, it is often absent in poorly differentiated tumors.

The presence of " traversing " capillaries is less specific and can be seen in

some metastatic lesions, particularly, renal cell carcinoma [38]. The key in

diagnosing a poorly differentiated HCC is to look for better differentiated

cells, with more typical hepatocytic features [48].

Immunocytochemistry is of little help in differentiating poorly

differentiated HCC from metastatic lesions because of a lack of highly

specific markers. Canalicular staining pattern with antibodies against

polyclonal carcinoembryonic antigen (pCEA) and diffuse positive staining

with endothelial cells markers (such as CD34, Factor VIII) can help

distinguish HCC from metastatic adenocarcinoma [38,49-51]. But positive

staining with these markers is least often identified in poorly

differentiated HCC. Another relatively new marker, HepPar1, has been shown

to be quite specific and sensitive as a marker for HCC. About 83% to 100% of

HCC stained positive with HepPar1 but only 4% to 15% of metastatic

carcinomas were positive [52,53]. Unfortunately, only 56% of poorly

differentiated HCC expressed HepPar1 [53].

Fibrolamellar variant of hepatocellular carcinoma

Fibrolamellar variant of HCC is rare, accounting for 1% to 2% of all cases

of HCC. However, it is important to recognize this variant because it has a

better prognosis [26]. It commonly occurs in patients younger than 35 years

and in a non-cirrhotic liver. The serum AFP level is often within normal

range. On radiological and gross examination, fibrolamellar variant of HCC

is characterized by a lobulated tumor mass with a central stellate scar. The

key diagnostic features on FNA are oncocytic neoplastic cells and lamellar

fibrosis. The neoplastic cells consist of abundant eosinophilic, granular

cytoplasm as a result of numerous swollen mitochondria [54]. Lamellar

fibrosis is represented by the presence of dense fibrous tissue with

parallel rows of bland fibroblasts.

Cholangiocarcinoma

Cholangiocarcinoma accounts for 10% of all primary hepatic malignancy and

affects elderly patients [26]. Cytologically, cholangiocarcinoma resembles

that of adenocarcinoma arising from pancreato-biliary tract and many other

sites [35] (Figure 4). Therefore, its distinction from HCC is usually

straightforward, except for poorly differentiated HCC. The presence of mucin

staining favors a diagnosis of cholangiocarcinoma over a HCC. In addition,

cholangiocarcinoma is rarely positive for AFP and HepPar 1 [52,55].

The diagnostic challenge for pathologists is to distinguish

cholangiocarcinoma from metastatic adenocarcinoma. Because of much overlap,

immunocytochemistry is not helpful in the differential diagnosis. As a

result, their distinction relies primarily on clinical history and

morphology. A history of known primary and the morphology of hepatic lesions

comparable to that of the primary tumor favor a diagnosis of metastatic

carcinoma over primary cholangiocarcinoma. There are also certain helpful

morphologic clues. For example, the presence of extensive necrosis and

columnar neoplastic cells with nuclear palisading would suggest a metastatic

colonic adenocarcinoma. Lobular mammary adenocarcinoma is often composed of

relatively monotonous neoplastic cells arranged in single file.

Vascular neoplasms

Hemangiomas are the most common benign tumor of the liver. They are often

asymptomatic and are detected incidentally in the work up of another

disease. Since radiologic imaging is often diagnostic of hemangiomas, they

are only occasionally evaluated by FNA. The aspirates are often bloody with

few cellular components including spindle-shaped endothelial cells,

capillaries, and fragments of fibrovascular connective tissue and smooth

muscle [56] (Figure 5). Suspected hemangioma is not considered an absolute

contraindication to FNA [57-59]. However, aspirating such lesions carries a

low risk of hemorrhage particularly when large needles are used.

Angiosarcomas are uncommon. Their clinical presentation is similar to that

of HCC. Liver function test is often deranged but the serum AFP level is not

elevated. Angiography may be helpful in diagnosis. Cytologically, the tumor

consists of single and loosely cohesive groups of pleomorphic spindle shaped

and/or epithelioid endothelial cells in a hemorrhagic and necrotic

background. Tubular structures, resembling capillaries, may be seen. The

differential diagnosis includes other sarcomas, both primary and metastatic.

Cystic hepatic lesions seldom undergo FNA. The differential diagnosis

includes a wide variety of reactive and neoplastic conditions. Infections

may result in cystic hepatic lesions including abscesses and hydatid cysts.

Liver abscess can be pyogenic and amoebic. Pyogenic abscesses are often

polymicrobial and consist of numerous neutrophils and necrotic tissue on

FNA. Amoebic abscesses, on the contrary, contain few or no neutrophils.

Periodic acid-Schiff (PAS) or iron stains are helpful in identifying

trophozoites which are seen in about one third of the cases [60].

Hydatid cysts are caused by the larvae of Echniococcus granulosis. The

diagnostic clue on cytology is the finding of scolices or hooklets in the

aspirates. Although a clinical suspicion of hydatid cyst is a

contraindication for FNA because of the risk of a fatal anaphylactic

reaction, no major complications have been reported even when hydatid cysts

are inadvertently aspirated [60].

Other non-neoplastic cysts, such as simple hepatic cyst and hepatic foregut

cyst, may be aspirated to rule out metastases in patients with a known

primary malignancy. The cytology typically consists of macrophages and few

bland appearing cuboidal, columnar, and/or squamous epithelial cells in a

background of proteinaeous fluid.

Among primary hepatic malignancies, biliary cystadenoma and

cystadenocarcinoma are most likely to present as a cystic lesion. They may

be an important source of false negative cytological diagnosis because the

aspirates are often paucicellular and consists of predominantly macrophages.

Figures

Figure 6

Hepatoblastom

Hepatoblastoma is the most common primary hepatic malignant neoplasm in

children. It is also the third most common intra-abdominal malignancy in

childhood, following neuroblastoma and Wilm's tumor. Affected children are

usually 3 years old or younger and have markedly elevated serum AFP level.

The male to female ratio is 2:1. Hepatoblastoma is not associated with

cirrhosis. There are 3 histological subtypes – epithelial, anaplastic, and

mixed (epithelial and mesenchymal) [35,61]. On cytology, the epithelial

component can show a spectrum of differentiation ranging from anaplastic to

embryonal to fetal [62]. Anaplastic cells morphologically resemble other

" small blue cell tumors " with a uniform population of small cells with scant

cytoplasm. Embryonal cells appear as small, oval to spindle shaped cells

arranged in cords, rosettes, or papillae (Figure 6). Individual cells have

large nuclei, small amount of cytoplasm, and prominent nucleoli. Fetal cells

are larger cells with more abundant granular and clear cytoplasm which may

contain bile, fat, or glycogen. They often arrange in disorderly trabeculae,

acini, and 3-dimensional clusters. The fetal cell type may be associated

with extramedullary hematopoesis. The mesenchymal component, when present,

appears primitive and undifferentiated.

The differential diagnosis includes HCC which can rarely occur in children.

It is important to separate HCC from hepatoblastoma because the latter has a

better prognosis [61]. Features that favor a diagnosis of HCC over

hepatoblastoma include patient's age greater than 10 years, presence of

liver cirrhosis, more definitive hepatic differentiation of neoplastic

cells, and the presence of marked pleomorphism and tumor giant cells [60].

Summary

FNA is a useful diagnostic test for evaluating patients with discrete

hepatic masses. However, liver FNA poses a number of diagnostic challenges.

Correlation with clinical, radiological, and cytological findings is helpful

in arriving at the correct diagnosis and therefore increases overall

accuracy and cost-effectiveness of the procedure.

Competing interests

None declared.

References <snip>

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