ISSN 2398-2985      

Biopsy overview

Jreptile

Synonym(s): Tissue sampling


Introduction

  • Standard technique to support diagnosis of inflammatory, proliferative, reactive and neoplastic conditions within tissue.
  • Biopsy refers to the collection of a sample of intact tissue for examination of tissue microarchitecture and structural change. This is distinct from cytopathology which is based on assessment of individual cells or groups of cells derived from a tissue lesion.        
  • Can be done under local anesthesia depending on individual and species, often requires sedation or general anesthesia.
  • Common conditions requiring biopsies:
    • Cutaneous masses or ulcerations for histopathology and often culture and sensitivity, eg fungal disease.
    • Organ biopsies, eg liver biopsies for confirmation of hepatic lipidosis.
    • Endoscopy is a very useful accompanying tool in obtaining biopsies in reptiles, eg liver biopsies in Chelonia.
  • Biopsy samples should be of sufficient size to allow for detailed analysis – obtaining large samples (cutaneous or organ samples) can be difficult in particularly small reptiles, eg geckos.

Uses

  • Confirmation of diagnosis or rule-outs.
  • Biopsies are taken to:
    • Establish a specific diagnosis.
    • Eliminate other clinical diagnoses.
    • Follow the course of the disease.
    • Confirm the completeness of excision of a tumor by evaluation of tumor margins. Additionally, biopsy evaluates the potential for metastatic spread of a neoplasm by evaluating vascular or lymphatic invasion.
  • Biopsy specimens are used for several clinical purposes including:
    • Histological diagnosis involving examination of hematoxylin and eosin-stained sections of tissue by light microscopy.
    • Special tests:
      • Application of histochemical stains to tissue, eg to detect organisms (Gram stain, periodic acid Schiff stain, Grocott stain or ZN stain) or evaluate the presence of collagen, fibrin, amyloid etc.
      • Immunohistochemistry/immunofluorescence, eg to specifically identify micro-organisms, to phenotype neoplastic cells, determine the nature of extracellular matrix tissue or identify deposits of immunoglobulin or complement within tissue lesions.
      • Fresh biopsy tissue may be submitted directly for microbial culture. Recommended to accompany with histopathology or immunohistochemistry to improve chances of detecting infectious agent.
      • Molecular diagnostics for example the use of polymerase chain reaction (PCR) for detection of infectious agent, or clonality testing to determine whether a lymphoid infiltration is reactive or neoplastic.
  • Types of biopsy include:
    • Bone marrow needle core biopsy Bone marrow aspiration.
    • Wedge biopsies are easier to perform in reptiles than punch biopsies due to the thin nature of the skin.
    • Incisional biopsy of viscera or mass lesions within viscera or skin.
    • Punch biopsy of skin.
    • Needle core biopsy of lymph node, liver, or kidney; rarely performed in reptiles.
    • Ultrasound-guided needle biopsy of internal viscera; rarely performed in reptiles.
    • Endoscopic biopsy of organs; a common tool for obtaining organ samples in reptiles.
    • Biopsy samples may be either fixed in neutral buffered formalin (generally) or fresh frozen for cryosectioning.
Ensure to always label samples correctly.

Advantages

  • Can be the most effective way to establish a definitive diagnosis.
  • Facilitates assessment of prognosis and treatment.
  • Excisional biopsy may result in cure if the biopsy procedure removes the lesion. Often performed in reptiles due to limitations of skin (thick scales, but overall skin thickness often very thin).

Disadvantages

  • Invasive in some cases and requires local or general anesthesia.
  • Correct tissue is not always accessible without complex procedures and additional equipment. Endoscopy often needed in reptiles for internal viscera sampling, especially in Chelonia.
  • Minor interference has been suggested to possibly exacerbate some neoplastic and reactive conditions although the evidence for this is limited.
  • Biopsy is a relatively slow diagnostic procedure:
    • Tissue samples require processing, so turn-around time is generally more than 24 h.
    • Longer if special fixing required, eg bone tissue or microorganism culture requested.

Requirements

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Preparation

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Procedure

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Aftercare

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Outcomes

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Prognosis

  • Good in all cases if planned properly.

Further Reading

Publications

Refereed papers

Other sources of information

  • Fraser M A & Girling S J (2019) Dermatology. In: BSAVA Manual of Reptiles. 3rd edn. BSAVA, UK. pp 260.
  • Gottdenker N & Yau Wilson (2019) Biopsy. In: Mader’s Reptile and Amphibian Medicine and Surgery. 3rd edn. Elsevier, USA. pp 365-367.

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