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Question 1

A 4-year-old female presents with 2-months of left knee swelling, decreased ROM, and pain. Associated symptoms include fatigue and low-grade fever to 100.5 F ocasionally. ANA positive. XR is shown. What is the diagnosis?

Answer 1

Acute lymphoblastic leukemia (ALL)

Question 2

An 11-year-old male presents with 6 months of left knee pain that has been slowly becoming more noticeable. It’s worse at night. They’ve tried Tylenol and Motrin; Motrin seems to work a little better, and he’s able to go back to bed. No fever. On exam, he has mild left knee swelling, mild antalgic gait, and mild muscle wasting to the affected side. XR is shown (ignore the caption!). What is the diagnosis?

Answer 2

Osteoid osteoma

Clinical

• Age: second decade, occasionally infants
• Sex ratio: 3 M : 1 F
• Insidious pain at night and responds well to NSAID c/w Tylenol
• Within nidus, there is a thousand-fold increase in prostaglandin concentration
• If intraarticular, may have joint swelling and limitation
• May also have gait disturbance, muscle wasting, scoliosis

Imaging

• Small < 15 mm and affect cortical bone, usually of long bones and less commonly vertebrae or carpal/tarsal bones
• XR is diagnostic: lytic lesion with surrounding sclerosis
• CT better visualizes lesion
• MRI: adjacent bone edema around nidus
• Bone scan: discrete area of increased activity

Question 3

A 16-year-old male presents with knee pain worse at night with swelling. On your exam, there is swelling adjacent to the knee that feels hard. XR is shown (ignore caption!). What is the diagnosis? With what conditions is there an increased risk of developing this diagnosis?

Answer 3

Osteosarcoma

Most common malignant bone tumor in kids

There is an increased risk with radiation exposure with 10-20 years latency

Most common sites: metaphysis or metadiaphysis of long bones like distal femur (40%), proximal tibia (20%), proximal humerus

Starts in medullary cavity and invades cortex, elevating periosteum and creating a classic Codman sign, then invades surrounding soft tissue to form the mass

May have pathologic fractures of skip lesions within same primary tumor

20% mets to lung or distant bones

Increased risk of developing osteosarcoma is a/w hereditary bilateral retinoblastoma, Li-Fraumeni syndrome or in Werner, Bloom, and Rothmund-Thomson syndromes

Question 4

A 10-year-old Caucasian male presents with intermittent pain in his left knee/leg that started 4 months ago. His mother became more concerned when she noticed swelling to the affected area. He developed a fever and review of his growth chart reveals he has not gained any weight in the last 6 months. Imaging is shown (ignore caption!)

1. What is the diagnosis?
2. What is the associated gene mutation?
3. What are the classic XR findings?

Answer 4

1. Ewing sarcoma
2. T(11;22) translocation. Oncogenic fusion protein (Basketball star Patrick Ewing’s number is 11 + 22 = 33)
3. XR: lytic lesion of diaphysis or within flat bones of axial skeleton, which may have onion skin appearance due to tumor lysis with periosteal reaction but may also have a spiculated pattern of new bone formation mimicking osteosarcoma. Cortex is breached with associated large soft tissue component
4. Mets can go to lung, bone, bone marrow

Question 5

An 11-year-old male presents with mild left distal leg knee pain and swelling. XR is shown (ignore caption!). His mother mentions that someone else in the family had similar symptoms.

1. What is the diagnosis?
2. What is the condition called when there is a positive family history and mulitple lesions?
3. What are the components of a lesion. Which part is neoplastic?
4. Can malignant transformation occur?
5. What mutation can the multiple lesions be associated with?

Answer 5

1. Osteochondroma
2. Mulitiple hereditary osteochondromatosis in 62% of patients with osteochondroma
3. Three components: perichondrium, cartilage cap, and bony stalk (pedunculated or sessile). Only cartilage cap is neoplastic
4. Malignant transformation to a secondary peripheral chondrosarcoma can occur in 1% of solitary and 5% of multiple
5. Multiple lesion formation a/w EXT1 (more severe phenotype) and EXT2 gene mutations

Question 6

A 13-year-old female presents with swelling of her middle finger. XR is shown (ignore caption!) What is the diagnosis?

Answer 6

Enchondroma

• Benign hyaline cartilage neoplasms of medullary bone
• Teenagers
• Female = male
• Hands and feet (50%), femur, humerus
• Usually solitary lesions but if multiple, called Ollier disease
• If associated with soft tissue hemangiomas, called Maffucci syndrome
• Nonfamilial disorders known to have mutant isocitrate dehydrogenase (IDH) pathways
• Calcification around the periphery of the lesion (bone encasement) is characteristic
• Malignant transformation to chondrosarcoma in 15-30% of multiple lesions

Question 7

An 8-year-old boy was evaluated in urgent care for leg pain after falling off a trampoline. XR is shown (ignore caption!). What is the diagnosis?

Answer 7

Fibrous cortical defect (Nonossifying fibroma)

Looks like Pacman bite out of bone

• Most common of all focal bone lesions, affecting up to 40% of kids 4-8 years old
• Asymptomatic and resolve spontaneously
• Most common sites: distal femur or proximal tibia near epiphyseal growth plate at site of tendon or ligament insertions
• Diagnosis: an incidental finding on XR
• XR: eccentric metaphyseal lucency with sclerotic margins

Question 8

A young female presents with a firm, slowly growing, painless swelling of the ankle. Imaging is shown (ignore caption!). What is the diagnosis?

Answer 8

Juvenile fibromatosis

Question 9

A female with cafe au lait spots and precocious puberty presents with leg pain and limp. XR as shown (ignore caption!). What is the diagnosis? What is the classic XR finding?

Answer 9

Fibrous Dysplasia

• Symptoms: Pain, gait disturbance, and growth deformity
• Monostotic (75%) or polyostotic (25%)
• Polyostotic form a/w cafe au lait spots, endocrine abnormalities like precocious puberty (McCune-Albright syndrome) or intramuscular myxomas (Mazabraud syndrome)
• Common sites: facial bones and ribs (especially with monostotic form) but also long bones
• XR: ground glass appearance of lesion with lack of trabeculae. Endosteal scalloping but without periosteal reaction (no Codman sign). Classic XR feature is the shepherd’s crook deformity of the femoral head, which can predispose to pathologic fracture

Question 10

A 13-year-old male presents with painful L third toe swelling. Imaging is shown. What is the diagnosis?

Answer 10

Giant cell tumor of tendon sheath, a pigmented villonodular synovitis isolated to the tendon sheath.

• Locally aggressive synovial proliferative disorder of unknown etiology affecting joints, tendon sheaths, and bursae
• Presents as painful, monoarticular effusion usually affecting the knee but can affect any joint. Rarely can be polyarticular.
• Consider PVNS in teen with painful monoarticular effusion with hemarthrosis (seen on joint aspiration and/or if response to intraarticular steroid injection is poor
• Histo: thickened reddish-brown synovium from hemosiderin deposition with numerous villous projections. Cytogenetics have monoclonality, suggesting it is neoplastic. Overexpression of CSF1
• XR: normal except for effusion or erosion
• MRI: low signal intensity T1 and T2 sequences within tissue with evidence of hemosiderin, which may even exaggerate the synovitis because of the blooming phenomenon caused by magnetic susceptibility effect to hemosiderin

Question 11

A 17-year-old female presents with left knee swelling and pain with adjacent muscle wasting of her quadriceps. She has been evaluated by dermatology previously for port wine lesions. Imaging is shown (ignore caption!). What is a serious complciation of this condition?

Answer 11

Juxtaarticular vascular malformations

• Pain and muscle wasting
• A/w Klippel-Trenaunay-Weber syndrome: juxtaarticular vascular malformations, cutaneous port wine lesions, varicose veins, limb hemihypertrophy
• If the malformation includes an intraarticular component, hemarthrosis can occur
• XR: phlebolith if there are juxtaarticular low-flow lesions
• Serious complication: Kasabach-Meritt phenomenon - consumptive coagulopathy with resultant severe thrombocytopenia

Question 12

A teenage male presents with a painless mass at the base of his thumb. He has a nearby enlarged lymph node. MRI is shown (ignore caption!). What is the diagnosis?

Answer 12

Rhabdomyosarcoma

• Extremity or truncal lesions are less common, affect primarily teens. Typically presents as painless mass with high incidence of regional LAD
• Most common soft tissue sarcoma in children
• Can arise in striated or smooth muscle anywhere, particularly head and neck and GU
• 20% of lesions occur in limbs
• A/w presence or absence of PAX/FOXO1 fusion gene
• Median age: 5 years. ⅔ presents before age 10

Question 13

A 12-year-old male presents with a painless swelling of his left knee/thigh. He had inguinal lymphadenopathy. XR revealed a lesion with calcification. MRI is shown (ignore caption!) What is the diagnosis?

Answer 13

Synovial sarcoma

• Most common non-rhabdomyosarcoma soft tissue sarcoma of childhood
• Male > female
• Rare in < 10 year old
• PResents as slowly growing painless mass in lower limb near tendon sheaths and bursae.
• The tumor spreads to regional LN and mets to lungs
• XR: calcifications in 30% of the cases
• Characteristic epithelial appearance is not consistent with synovium and tumors are usually not in the joint

Question 14

What is the pediatric malignancy with the highest incidence of bony mets?

Answer 14

Neuroblastoma

Question 15

A 4-year-old female presents with leg pain and abdominal pain. She is irritable and refusing to walk. She has had poor weight gain recently and appears pale. She has purple bruising around her eyes. XR and MRI of her thighs is shown (ignore caption!).

1. What is the diagnosis?
2. What labs are typically elevated?
3. What is a pathognomonic clinical feature?

Answer 15

Neuroblastoma

1. Neuroblastoma
2. Homovanillic acid, dopamine, adrenaline, noradrenaline in urine. Ferritin.
3. Raccoon eyes due to orbital mets

Question 16

What presents with pain or pathologic fracture involving metaphysis of proximal humerus or femur presenting in later childhood?

Answer 16

Unicameral Bone Cyst

Question 17

An adolescent female presents with pain of her low back/pelvis. CT (left) and MRI (right) is shown (ignore caption!). What is the diagnosis?

Answer 17

Aneurysmal bone cyst

• Related to translocation of ubiquitin carboxylase-terminal hydrolase 6 oncogene on chromosome 17

Question 18

What most commonly presents as a well-defined lytic lesion of the skull but can also present as pain in a long bone or vertebrae with 2/2 signs of nerve root or cord compression in a 4-year-old child? Imaging is shown (ignore caption!)

Answer 18

Langerhans Cell Histiocytosis

• Bony lesions occur in children < 10 yo with peak incidence at age 3-5
• Most common site is skull but any long bone or vertebrae may be involved
• Lesions in weight-bearing bones or in the spine usually present with pain
• Could have signs of nerve root or cord compression with spinal lesions
• Spinal involvement could cause vertebral body collapse, causing vertebrae plana
• Posterior pituitary involvement with resultant diabetes insipidus and potential growth hormone deficiency may accompany bony lesions of the base of the skull in young children
• Thought to be due to immune dysregulation rather than true malignancy
• No mets
• Some spontaneously resolve
• Prognosis excellent for those without systemic involvement
• XR: well-defined lytic lesions but some areas may show periosteal reaction

Question 19

A 14-year-old male presents with 2 months of malaise, fatigue, headache, weight loss and 2 weeks of headache, intermittent abdominal pain and now he has a low-grade fever. His BP is 145/90. His labs show evidence of systemic inflammation. MRI is shown (ignore caption!) What is the diagnosis?

Answer 19

Takayasu arteritis

Question 20

A previously healthy 7-year-old girl has a 4-day history of fever, myalgias, and rash. Last week she had a sore throat that resolved without intervention. She is currently febrile and appears mildly uncomfortable. She has a temperature of 38°C, heart rate of 105 beats/min, respiratory rate of 20 breaths/min, oxygen saturation of 100% on room air, and blood pressure of 102/68 mm Hg. A review of systems reveals only fever, myalgias, and rash. She has no cough, nasal congestion, sinus pain, Raynaud syndrome, joint swelling, abdominal pain, or blood in the stool.

There are tender, erythematous nodules scattered on her hands and lower extremities, particularly the plantar surface of the distal toes. There is mottling of the dorsum of the foot and dusky discoloration of the first through fourth toes bilaterally (Figure). She also has areas of purple, netlike mottling on her upper legs. The physical examination findings are otherwise normal. She has normal heart sounds without murmur, lungs clear to auscultation, a soft and nontender abdomen without organomegaly, and full range of motion of joints without swelling.

Laboratory data are shown:

White blood cell count 11,000/µL (11 × 109/L)

Hemoglobin 12.6 g/dL (126 g/L)

Platelet count 385 × 103/µL (385 × 109/L)

Erythrocyte sedimentation rate 85 mm/h

Complete metabolic panel Normal

Antinuclear antibody Negative

Urinalysis Normal

Antistreptolysin O 2,000 IU

Of the following, the MOST likely diagnosis is

A. antineutrophil cytoplasmic antibody–associated vasculitis

B.cutaneous polyarteritis nodosa

C. rheumatic fever

D. systemic polyarteritis nodosa

Answer 20

B.cutaneous polyarteritis nodosa

This vignette describes the typical presentation of cutaneous polyarteritis nodosa (cPAN), which is best diagnosed via biopsy. The hallmark of cPAN is the presence of tender, erythematous to violaceous, subcutaneous nodules. Fever and myalgia are common associated symptoms. In children, cPAN is often preceded by group A streptococcal infection.

Why ARF is the WRONG answer:

This patient had a recent episode of pharyngitis that resolved without intervention. This episode might lead to consideration of acute rheumatic fever (ARF), which causes fever and systemic inflammation, as seen in this vignette. However, the rash (Figure) does not resemble erythema marginatum. Additionally, other signs and symptoms of ARF, such as cardiac involvement and arthritis, are absent. The nodules of ARF are not erythematous or tender.