A 35-year-old woman presents with a 6-month history of progressive pain and stiffness in the proximal humerus. On examination, there is mild limitation of shoulder abduction. Plain radiographs show a well-defined, sclerotic lesion in the proximal humeral metaphysis with a narrow zone of transition and a surrounding rim of sclerosis. There is no periosteal reaction or cortical destruction. CT imaging reveals internal calcification with a popcorn-like or chondroid appearance. MRI shows low-signal lesion with areas of high signal fat planes between the lesion and surrounding bone. Which is the most likely diagnosis?

Explanation

## Clinical Presentation and Imaging Correlation **Key Point:** Vertebral hemangioma is the most common benign vascular tumor of bone, but hemangiomas can occur in any bone. In the proximal humerus, hemangioma presents with a well-defined sclerotic lesion with a narrow zone of transition, no periosteal reaction, and characteristic MRI findings of high-signal fat planes (due to fatty stroma between vascular channels). ### Why Hemangioma Fits This Case The imaging triad described is classic for **intraosseous hemangioma**: 1. **Well-defined sclerotic lesion with narrow zone of transition** — reflects slow-growing, benign nature 2. **Surrounding rim of sclerosis** — reactive bone formation around the lesion 3. **No periosteal reaction or cortical destruction** — benign, non-aggressive 4. **CT: internal calcification with popcorn-like appearance** — coarse trabecular pattern within hemangioma 5. **MRI: low-signal lesion with areas of high-signal fat planes** — the hallmark of hemangioma; fat signal between vascular channels is pathognomonic **High-Yield:** The **high-signal fat planes on MRI** between the lesion and surrounding bone is the single most distinguishing feature of intraosseous hemangioma. This reflects the fatty marrow interspersed between the vascular sinusoids and is NOT seen in chondrosarcoma, osteosarcoma, or enchondroma. ### Comparative Imaging Features | Feature | Hemangioma | Chondrosarcoma | Osteosarcoma | Enchondroma | |---------|------------|----------------|--------------|-------------| | **Age** | Any age | 30–60 years | 10–25 years | 20–40 years | | **MRI fat signal** | **Present (pathognomonic)** | Absent | Absent | Absent | | **Calcification** | Coarse trabecular | Popcorn/chondroid | Fine stippled | Fine stippled | | **Periosteal reaction** | Absent | Minimal | Sunburst/Codman | Absent | | **Cortical destruction** | Absent | Absent/minimal | Present | Absent | | **Zone of transition** | Narrow | Narrow | Wide | Narrow | ### Why Other Options Are Incorrect - **A) Chondrosarcoma** — Would show chondroid matrix calcification on CT, but MRI would show lobulated cartilage signal (high T2), NOT high-signal fat planes. Chondrosarcoma does not produce fat signal on MRI. - **B) Osteosarcoma** — Typically in adolescents/young adults; shows wide zone of transition, periosteal reaction (sunburst/Codman triangle), and cortical destruction — none of which are present here. - **C) Enchondroma with malignant transformation** — Would require a history of a previously known lesion; malignant transformation would show cortical destruction or periosteal reaction. The fat planes on MRI are not a feature of enchondroma. **Clinical Pearl:** The key discriminator in this vignette is the **MRI finding of high-signal fat planes between the lesion and surrounding bone** — this is pathognomonic for intraosseous hemangioma (Helms CA, Fundamentals of Skeletal Radiology 4e). No other bone tumor produces this finding. **Mnemonic: HEMA** — **H**igh fat signal on MRI, **E**xpansile but benign, **M**etaphysis/diaphysis, **A**ny age. [cite:Helms CA Fundamentals of Skeletal Radiology 4e Ch 9; Resnick D Diagnosis of Bone and Joint Disorders 4e]