Is it appropriate for a primary‑care physician to refer a patient with a diagnosed benign enchondroma of the femur to orthopedics?

Orthopedic Referral for Benign Enchondroma of Femur

Yes, orthopedic referral is reasonable and appropriate for a patient with a diagnosed benign enchondroma of the femur, particularly if the patient is symptomatic, the lesion is large, or there are any concerning radiographic features. 1

Clinical Context and Risk Assessment

The femur represents a higher-risk location for enchondromas compared to small bones of the hands and feet. The femur is one of the sites with the highest rates of malignant transformation to chondrosarcoma (along with tibia, humerus, pelvis, and scapula), with transformation occurring in approximately 30% of patients with enchondromatosis syndromes. 1 While solitary enchondromas have much lower malignancy risk than multiple enchondromas, femoral location warrants closer attention. 2

Key Clinical Red Flags Requiring Immediate Referral

• Pain at the lesion site is the most important clinical indicator of potential malignancy or active growth, even in radiographically "benign-appearing" lesions 3, 4
• Progressive symptoms or increasing pain suggest possible malignant transformation 3
• Lesion size >5-6 cm or location in the proximal femur (neck/head) increases concern 1, 5
• Cortical scalloping, erosion, lytic areas, cortical breaks, or soft tissue extension on imaging 4

Rationale for Orthopedic Referral

Diagnostic Uncertainty in Femoral Enchondromas

Distinguishing benign enchondroma from atypical cartilaginous tumor/grade I chondrosarcoma is notoriously difficult, even for expert pathologists, and radiographic features frequently overlap. 1, 3, 6 Studies show that radiographs suggest the correct diagnosis of enchondroma in only 67.2% of cases and correctly identify grade 1 chondrosarcoma in only 20.8% of cases. 1

In the humerus and other long bones, central cartilaginous lesions should be considered atypical cartilaginous tumors until proven otherwise. 6 This same principle applies to femoral lesions given their similar anatomic characteristics.

Management Expertise Required

Orthopedic surgeons with musculoskeletal tumor expertise can provide:

• Proper surveillance protocols including serial radiographs every 2-3 years for known lesions 1
• Advanced imaging interpretation including contrast-enhanced MRI to identify high-grade areas if clinical concern develops 3, 6
• Surgical planning if intervention becomes necessary, including curettage with or without local adjuvants for symptomatic lesions 3, 7, 5
• Recognition of when specialized sarcoma center referral is needed if malignancy is suspected 1, 8

Common Pitfalls to Avoid

Do not assume all "benign-appearing" enchondromas can be safely observed without specialist input, especially in the femur. 4, 2 Studies show that even small, well-defined lesions are frequently confused with sarcoma or other malignancies, often due to lack of education on bone tumors among general practitioners and radiologists. 4

Do not perform biopsy before specialist consultation. If malignancy becomes suspected, all patients with radiologically suspected primary malignant bone tumors must be referred to a bone sarcoma reference center before any biopsy is performed. 1, 8

Recognize that approximately 65% of patients with incidentally discovered enchondromas have adjacent joint problems that are the actual source of symptoms. 4 However, pain directly at the lesion site remains concerning for malignancy. 3

Practical Referral Algorithm

Refer to orthopedics if ANY of the following are present:

• Symptomatic lesion with pain at the tumor site 3, 4
• Femoral neck or head location 7, 5
• Lesion >3-5 cm in size 1, 4
• Any aggressive radiographic features (scalloping, cortical erosion, soft tissue extension) 4
• Patient or physician anxiety about the diagnosis 9

Consider observation with primary care follow-up only if:

• Completely asymptomatic incidental finding 4
• Small lesion (<3 cm) in femoral diaphysis 1
• Classic benign radiographic appearance with punctate calcifications 4, 7
• Patient understands need for symptom monitoring and has reliable follow-up 2

Even in observation scenarios, establishing a relationship with orthopedics for potential future consultation is prudent given the femoral location and long-term malignant transformation risk. 1, 2