X-ray is the Next Investigation
Plain radiographs in two planes should always be the first investigation for any suspected bone or deep tissue lesion presenting as a well-demarcated, red, painful thigh lesion, as they are rapid, inexpensive, and provide critical information about whether deeper structures are involved. 1
Why X-ray First, Not Biopsy
The fundamental principle in evaluating a painful, well-demarcated lesion is to never biopsy before adequate imaging, as this can contaminate tissue planes and compromise future surgical management if malignancy is present. 1, 2 This is particularly critical because:
- Pain, especially persistent or night pain, warrants radiological assessment to exclude bone pathology before any tissue sampling is performed 1
- A superficial-appearing red lesion could represent overlying cellulitis from underlying osteomyelitis or a bone tumor breaking through the cortex 1
- The American College of Radiology specifically recommends plain X-ray as first-line imaging for any suspected bone or deep tissue pathology due to its ability to identify bone destruction, periosteal reaction, soft tissue calcification, or gas formation 1
What the X-ray Will Show
Plain radiographs will rapidly determine:
- Whether bone is involved (destruction, periosteal reaction, or calcification) 1
- Presence of soft tissue gas suggesting infection 1
- Whether deeper structures require further evaluation with MRI 1, 2
Algorithm After X-ray Results
If X-ray Shows Normal Findings
- Proceed to MRI to evaluate soft tissue and bone marrow if symptoms persist 1
- Consider punch biopsy only after imaging excludes deep pathology 1
If X-ray Shows Suspicious Bone Lesion
- MRI of the whole bone with adjacent joints for staging 1, 2
- Referral to a specialized bone sarcoma center before any biopsy 2, 1
- The biopsy must be performed at the reference center by the surgeon who will carry out definitive resection, as improper biopsy technique can contaminate tissues 2, 3
Why Other Options Are Incorrect
Punch biopsy (Option A) without prior imaging violates the fundamental principle that prevents tissue contamination and allows proper surgical planning if malignancy is discovered 1, 2
MRI (Option B) is indicated only when malignancy cannot be excluded with certainty on plain radiographs, making it the second step, not the first 1, 2
Ultrasound (Option D) is not the standard first-line investigation for painful bone or deep tissue lesions, as plain radiographs provide superior information about bone involvement 1