What are the next steps for a young adult patient with a provisional diagnosis of osteochondroma based on MRI, now that a surgical specimen is available for histopathological examination?

Histopathological Examination of Osteochondroma Surgical Specimen

Immediate Verification Steps

Before proceeding with routine processing, confirm that the specimen was obtained from a specialized bone sarcoma center, as improper biopsy technique or excision outside reference centers can compromise diagnosis and future management. 1, 2, 3

Critical Pre-Processing Requirements

• Verify the request form contains sufficient clinical details including: patient age, exact anatomical site of the tumor, duration and character of symptoms (particularly night pain), and complete radiological differential diagnosis with imaging findings 1
• Confirm whether the patient received any preoperative chemotherapy, as this affects histological interpretation 1
• Document the nature of the specimen received: whether it is a needle biopsy, curettage, excision, segmental resection, or other complex resection 1

Specimen Handling Protocol

Immediate Processing (Within 30 Minutes)

• Take tumor imprints (touch preps) before formalin fixation for potential tumor-specific translocation analysis by FISH 1
• Preserve tissue/cell suspensions frozen in cryomolds to enable future molecular pathology assessments 1
• Consider establishing primary cell cultures for cytogenetics and other studies 1
• Obtain informed consent for tumor banking if not already secured, enabling later analyses and research per local regulations 1

Specimen Documentation

• Record the size of the tumor measured in three dimensions (mm) in the resected bone 1
• Note any surgical markings: haemo-clips placed on risk areas or marginal margins, areas marked as suspicious for close margins 1
• Document the extent of local tumor spread including involvement of specific anatomical compartments (bone, nerves, muscle, joint, growth plate cartilage, vessels) 1

Decalcification and Sectioning

• Decalcification is usually necessary for bone tumor specimens 1
• Section to identify the cartilage cap thickness, as caps >2.0-3.0 cm raise concern for malignant transformation to chondrosarcoma 1, 4
• Sample any areas that appear high-grade or atypical on gross examination, as osteochondromas can harbor foci of chondrosarcoma 1

Histological Assessment Requirements

Confirm Diagnosis

• Verify whether the resection specimen diagnosis confirms the biopsy diagnosis (if prior biopsy was performed) 1
• Describe histological features and specify tumor type/subtype according to WHO Classification 1
• Apply SNOMED or ICD-O codes for classification 1

Critical Diagnostic Pitfall

Differentiation between benign osteochondroma and grade I chondrosarcoma is notoriously difficult even for expert pathologists, with significant interobserver variability. 4 In cases of diagnostic uncertainty:

• Look for features suggesting malignant transformation: increased cellularity, nuclear atypia, myxoid change in the cartilage cap, permeation of trabecular bone 1
• Correlate with clinical features: new or increasing pain, rapid growth in adulthood, cartilage cap >2.0 cm on imaging 1, 4, 5
• Consider that secondary peripheral chondrosarcomas arise from pre-existing osteochondromas, particularly in patients with hereditary multiple osteochondromas (1-5% transformation risk) 1

Margin Assessment

• Measure and document the distance (in mm) of tumor from the nearest resection margin 1
• Note whether resection margins are clear or involved by tumor 1
• Pay special attention to margins at risk locations marked by the surgeon with clips or ink 1

Ancillary Studies

• Record results of relevant immunohistochemistry if performed 1
• Consider molecular studies if tissue was appropriately preserved and diagnosis remains uncertain 1

Reporting Requirements

Essential Elements in Final Report

• Confirm the diagnosis: benign osteochondroma versus low-grade chondrosarcoma versus higher-grade malignancy 1
• Address the surgical question: Can the surgery be considered successful based on resection margins? 1
• Provide prognostic information: histological grade if malignancy is identified 1
• Note any unexpected findings that differ from the provisional MRI diagnosis 5

Post-Reporting Recommendations

All cases should be discussed at a multidisciplinary team meeting including the radiologist who interpreted imaging, the pathologist who reviewed the specimen, and the surgeon and oncologist undertaking treatment to minimize errors in diagnosis and staging 1

Special Surveillance Considerations

If the diagnosis confirms benign osteochondroma but concerning features exist:

• Recommend clinical follow-up for patients with large lesions (>5-6 cm), pelvic/scapular location, or hereditary multiple osteochondromas 1, 4
• Suggest periodic imaging if the patient has risk factors for malignant transformation 1, 4