What is the recommended course of action for a 1.0 cm purple/blue tone lump on the lateral aspect of the 5th digit on the right hand with mild tenderness?

Recommended Management of Purple/Blue Lump on 5th Digit

This lesion requires immediate plain X-ray imaging before any biopsy or other intervention to exclude underlying bone pathology or deep tissue involvement. 1

Initial Diagnostic Approach

The clinical presentation of a 1.0 cm purple/blue lump with mild tenderness on the lateral aspect of the 5th digit raises concern for several possibilities, including glomus tumor, vascular malformation, subungual melanoma, or even underlying bone pathology presenting with overlying soft tissue changes. The key principle is that imaging must precede tissue sampling to avoid contaminating tissue planes if malignancy is present. 1

Mandatory First Step: Plain Radiography

• Obtain plain X-rays in two planes of the affected digit immediately as the first-line investigation, as this is rapid, inexpensive, and provides critical information about whether deeper structures (bone) are involved 1
• The presence of pain, even if mild, warrants radiological assessment to exclude bone pathology such as enchondroma, bone tumor, or osteomyelitis 1
• Never assume a superficial presentation means superficial disease – a purple/blue painful lesion could represent overlying changes from underlying osteomyelitis or a bone tumor breaking through the cortex 1

Critical Pitfall to Avoid

• Do not perform punch biopsy or excisional biopsy before obtaining X-ray imaging, as this fundamental principle prevents tissue contamination and allows proper surgical planning if malignancy is discovered 1
• Biopsy before adequate imaging can compromise future surgical management if bone involvement or malignancy is present 1

Next Steps Based on X-ray Results

If X-ray Shows Normal Bone

• Proceed with excisional biopsy with 1-3 mm margins for definitive diagnosis, as this is the preferred approach for suspicious pigmented or vascular lesions on digits 2
• The biopsy should be full-thickness and oriented longitudinally along the digit to facilitate potential future wide excision if needed 2
• Ensure the specimen is evaluated by a pathologist experienced in pigmented lesions and soft tissue tumors 2

If X-ray Shows Suspicious Bone Lesion

• Obtain MRI of the entire digit including adjacent joints for staging before any biopsy 1
• Refer to a specialized orthopedic oncology or hand surgery center before performing biopsy 1
• MRI is indicated when malignancy cannot be excluded with certainty on plain radiographs 1

Differential Diagnosis Considerations

The purple/blue coloration with mild tenderness in this location suggests:

• Glomus tumor (most common benign vascular tumor of the digit, typically exquisitely tender)
• Subungual or periungual melanoma (requires full-thickness biopsy for accurate Breslow thickness measurement) 2
• Vascular malformation or hemangioma
• Underlying bone pathology with overlying soft tissue changes 1

Specific Management if Melanoma is Suspected

If the clinical appearance raises concern for melanoma:

• Full-thickness incisional or punch biopsy of the clinically thickest portion is acceptable for digits, as excisional biopsy may be inappropriate in this anatomic location 2
• Shave biopsy should be avoided as it may compromise pathologic diagnosis and complete assessment of Breslow thickness 2
• The pathology report must include Breslow thickness, histologic ulceration, dermal mitotic rate, and margin status 2

Summary Algorithm

1. Plain X-ray in two planes (mandatory first step) 1
2. If X-ray normal: Proceed with excisional biopsy with 1-3 mm margins 2
3. If X-ray abnormal: MRI followed by referral to specialized center before biopsy 1
4. Never biopsy before imaging 1