Fine Needle Aspirate and Cytology of the Liver

Introduction:  Fine needle aspirate (FNA) may be used to determine cell types present, but does not provide information about the architecture of the liver.  FNA and cytology combined may provide enough information to aid in the diagnosis of certain diffuse liver diseases, including hepatic lipidosis and diffuse lymphoma.  If results from FNA and cytology are inconclusive, a percutaneous needle biopsy or wedge biopsy may required.  Biopsies should be submitted for histopathology in cases where assessment of liver architecture is imperative for diagnosis.


Indications:  Fine needle aspirate and cytology are indicated when diffuse liver disease is present or suspected. 


Contraindications:


FNA or biopsy of the liver may be contraindicated if a coagulopathy exists.  One of the functions of the liver is to make clotting factors, thus an animal with diffuse hepatopathy may be at risk for hemorrhage following one of these procedures.  There is thought to be less risk of hemorrhage with a FNA than with a biopsy, if both are ultrasound guided.  Prothrombin time (OSPT)  and partial thromboplastin time (APTT) should be done to evaluate clotting ability before initiating FNA or biopsy on an animal with liver disease.  If clotting times are prolonged, a blood transfusion to supply clotting factors should be given before proceeding with FNA or biopsy.  There is risk of puncturing the stomach, intestines, or biliary system, which may be reduced by using an ultrasound-guided technique.  


FNA may be contraindicated if there is a bile duct obstruction, as rupture of the biliary system will cause a bile peritonitis.  


FNA may also be contraindicated if an abscess is suspected, in which case an exploratory laparotomy should be performed instead.


Procedure:  This is a simple procedure, and does not require general anesthesia.  A 22 or 25 gauge needle and 10 or 12 ml syringe are used.  The needle is advanced into the liver (ultrasound may be used concurrently to assure the needle is in the liver), and suction is applied to the syringe multiple times until fluid/cells appear in the hub.  Suction is then released and the needle withdrawn.  The cells are expelled onto a glass slide and smears are made.  The slides are then dried and stained so that cells can be examined under microscope.


Histopathology:

Cells were collected by FNA.  The predominant cells in an aspirate of normal liver will be rafts of hepatocytes.  

Remember, this finding does not necessarily rule out significant liver pathology since it is only a small sample of the entire liver.

Click on the picture for an enlarged view.

 

Fatty change: Cells obtained by FNA in an animal with hepatic lipidosis are expected to show  vacuolation due to lipid accumulation.  Lipid can be confirmed with an Oil-Red-O stain (will stain lipids red). 

                     Click on the picture for an enlarged view.

 

Lymphoma:  In hepatic lymphoma, the predominant cell type is a homogenous population of immature lymphoid cells.  Although this cytology is taken from a lymph node, it shows the large lymphoblasts that may be aspirated from the liver if it is infiltrated with these neoplastic cells.

                Click on the picture for an enlarged view.

 


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