Biopsy principles in orthopedics
Synonyms and keywords: Bone biopsy, Soft tissue biopsy, Biopsy in musculoskeletal system

# Overview
Biopsy is the gold standard test for the diagnosis of bone and soft tissue tumors. The tumor is then staged based on Enneking system for for benign and malignant bone tumors.

## Biopsy
- Biopsy is the gold standard test for the diagnosis of  bone and soft tissue tumors.

## Indications
- Aggressive bone or soft tissue lesions.
- Soft tissue lesions more than 5 cms.
- Soft tissue lesions deep to fascia.
- Soft tissue lesions overlying bone or neurovascular structures.
- When diagnosis is unclear despite patient being symptomatic.
- Solitary bone lesions in a patient with history of carcinoma.

## Contraindications
- Asymptomatic latent bone lesions.
- Symptomatic benign active bone lesions confirmed on imaging studies.
- Asymptomatic soft tissue lesion which are completely benign on MRI such as lipoma and hemangioma.
Prerequisites for a Biopsy
- CBC, platelets and coagulation studies should be done.
- Cross-sectional imaging to evaluate local anatomy such CT scan and MRI.
- Treatment center carrying out biopsy must be capable of proper diagnosis and treatment.
- The surgeon who performs biopsy should preferably be the one who is later going to do the final excision.
Technique
- Open
- Closed

## Open Technique
- The tumor is surgically exposed and biopsy of the tumor is taken.

## Types

## Incisional biopsy
- A small surgical incision carefully placed to access tumor without contamination of critical structures.

## Excisional biopsy
- It is done for small, superficial soft tissue masses.
Incision
- Longitudinal incision in the extremities is taken.
- It should allow for extension of the incision for definitive management.
Approach
- Never expose neurovascular structures during the procedure.
- During the biopsy, all tissue exposed is considered contaminated with tumor.
- Meticulous hemostasis must be carried out.
- Post-surgery hematomas are considered contaminated with tumor.
- Always deflate the tourniquet prior to wound closure.
Biopsy
- Perform through the involved compartment of the tumor.
- For bone lesions with a soft tissue mass, perform the biopsy using the soft tissue mass.
Closure
- If drain is kept, remove the drain out of the skin in line with surgical incision.
- This helps in excising the drain site with definitive surgical extensive incision.

## Closed Technique

## Types

## Fine Needle Aspiration (FNA)
- It provides cytologic specimen.
- It is the most commonly used for carcinoma.
- It is usually not preferred for sarcoma.

## Core biopsy (Tru-cut Biopsy)
- It allows for tumor structural examination.
- It allows evaluation of both the cytologic and stromal elements of the tumor.
- It is frequently used for sarcomas.
- The various investigations must be performed in the following order:
- X-ray
MRI
- X-ray
- MRI
- Biopsy

## Staging

## Enneking (MSTS) Staging System
- The Enneking surgical staging system (also known as the MSTS system) for benign musculoskeletal tumors based on radiographic characteristics of the tumor host margin.
- It is widely accepted and routinely used classification.
- The Enneking surgical staging system (also known as the MSTS system) for malignant musculoskeletal tumors based on histological and radiographic characteristics of the tumor host margin.