summary Periosteal Chondromas are rare, benign, chondrogenic tumors that occur on the surface of long bones, most commonly the proximal humerus. Patients typically present between the ages of 10 and 20 years of age with regional pain secondary to irritation of overlying tendons. Diagnosis is made with radiographs showing a well-demarcated, shallow cortical defect with saucerization of the underlying bone. Treatment is usually observation. Marginal surgical excision of the lesion, including the underlying cortex, is indicated in patients with severe and progressive pain. Epidemiology Demographics occur in 10-20 year-olds Anatomic location the surface of long bones (under periosteum) in distal femur, proximal humerus, and proximal femur 59% of lesions in proximal humerus other locations in the hand (metacarpal or phalanges) Presentation Symptoms many are painful secondary to irritation of tendons Imaging Radiographs well-demarcated, shallow cortical defect punctate mineralization (calcification) in 1/3. saucerization of underlying bone radiographs important to differentiate from chondrosarcoma (histology may be similar) Studies Histology similar to enchondroma except for increased cellularity and more malignant looking cells (can look like chondrosarcoma) bland hyaline cartilage small chondroid cells in lacunar spaces Differentials Differential of Periosteal Chondromas Surface Lesion May have similar chondrogenic histology Treated with marginal excision Periosteal chondroma o o o Osteochondroma / MHE o Parosteal osteosarcoma o Periosteal osteosarcoma o Enchondroma / Olliers / Marfuccis o Osteochondroma (MHE) o Chondrosarcoma o Neurilemoma (soft tissue) o Nodular fasciitis (soft tissue) o Epidermal inclusion cyst o Glomus tumor o Treatment Operative marginal excision including underlying cortex indications severe symptoms interferring with function technique lesion will recur if cartilage is left behind bone graft any large defects