Le Trong Binh, MD

 A 20-year-old female admitted to the hospital complaining about a vague mild pain in her left knee joint area. She first noticed the pain several months ago without impact on her daily activities. Physical examination was unremarkable for knee joint effusion or swelling, deformity or activity limitation. She denied any history of injury to the knee. Laboratory test was normal for inflammation or rheumatoid.

Laboratory test was normal for inflammation or rheumatoid.

 Frontal and lateral radiograph of the left knee demonstrate a geographic well-defined lytic lesion (white arrow) in the metadiaphysis of the distal femur with a sharp zone of transition. The long axis of the lesion parallels that of the long axis of the femur. There is no evidence of bone expansion, erosion or periosteal reaction. Overlying cortex remains intact. This finding is suggestive of a simple (unicameral) bone cyst, type IA according to Lodwick classification.

 CT scan reveals a simple bone cyst in the distal metaphyseal region of the left femur. The cyst is centrally located in the medullary cavity of the femur with unremarkable expansion and thinning of the overlying bony cortex. No evidence of pathological fracture, fallen fragment or calcification.

 On MRI, the lesion appears as relatively homogenous hypointense on T1W and hyperintense on T2W, T2 FLAIR and STIR which is consistent with simple bone cyst.

 Simple or unicameral bone cysts (UBC) are expansile, serous-fluid-containing defects that are not true neoplasms. This lesion was first described by Virchow R in 1876 and then was recognized by Bloodgood as a different entity from other cystic bone lesions in 1910. Jaffe and Lichtenstein provided a detailed discussion of simple bone cysts in 1942. Peak age ranges between 3-14 years in 80 percent of cases. The incidence is estimated at 3 percent of all bone lesions, with a male to female ratio of 2:1. The majority of these cysts occur in the proximal humerus (70 percent) and femur (25 percent).

 While exact figures are unknown, it is estimated that approximately 75 percent of children present with pathologic fracture. Cysts heal in less than 15 percent of children following fracture. Although unicameral bone cysts are believed to resolve with skeletal maturity, without treatment these children are at risk for pain, or recurrent fracture leading to activity restriction for many years. Many theories have been proposed to explain the pathogenesis of unicameral bone cysts. An early theory was that injury to the growth plate leads to abnormal endochondral bone formation. Another theory suggests that vascular obstruction causes cyst fluid to accumulate under pressure and expand at the expense of the normal bone. Other theories include blocked fluid drainage, increased lysosomal enzyme activity, prostaglandins, nitric oxide, oxygen free radicals, disorders of synovial origin and genetic causes.

 As these hypotheses concerning the pathogenesis of UBCs have evolved, various methods of treatment of unicameral bone cysts have been proposed, such as treatment with open curettage with bone-grafting, intralesional injection of steroids, autologous bone marrow, percutaneous injection of allogenic demineralized bone matrix, and percutaneous curettage and bone grafting with widely variable success rate.

Simple bone cysts usually present as well-defined, geographic lesions with narrow transition zones on radiograph. A thin sclerotic margin is a typical finding. Simple bone cysts are usually situated in the intramedullary metaphyseal region immediately adjacent to the physis. Occasionally, they may be diaphyseal. The long axis of the lesion parallels to that of the long axis of the tubular bone. Lesions may cause expansion of the bone with thinning of the overlying cortex. Some may have a multilocular appearance. In long bones, simple bone cysts are typically centrally located within the medullary cavity. A pathologic fracture through a simple bone cyst is a common occurrence. This may lead to the "fallen fragment" sign, which describes the migration of a fragment of bone to a dependent portion of the fluid-filled cyst. It occurs in only a minority of patients. This sign is an important differentiating feature between a simple bone cyst and other nonlytic bone lesions. When present, the fallen fragment sign is pathognomonic of a simple bone cyst. Radiography usually is sufficient to confirm the diagnosis of simple bone cysts.

CT scan is often unnecessary in the evaluation of simple bone cysts because of the high accuracy of diagnosis of radiography. CT is occasionally used in the evaluation of lesions observed in areas difficult to assess on plain radiography, such as the spine and pelvis. The role of CT is to determine the extent of the lesion as well as to detect subtle complications difficult to evaluate on plain radiography. The features of a simple bone cyst observed on plain radiography also can be appreciated on CT. Occasionally, air and air-fluid levels may be seen within simple bone cysts. Fluid-fluid levels also may be noted. Dynamic CT scan may help in differentiating a fluid-containing simple bone cyst, which is avascular, from other solid benign bone lesions that demonstrate varying degrees of vascularity. The presence of a fallen fragment sign on CT is diagnostic of a simple bone cyst. CT has high sensitivity and specificity for detecting simple bone cysts.

MRI can confirm the presence of fluid within a simple bone cyst. Uncomplicated simple bone cysts have low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Lesions that have a pathologic fracture have heterogeneous signal intensities on both T1- and T2-weighted images because of bleeding within the cyst. With gado enhancement, they demonstrate enhancement with focal, thick peripheral, heterogeneous or subcortical patterns. Septations within the lesions may be observed on MRI and may not be visualized on radiographs. MRI reveals the presence of thin reparative tissue lining the cyst wall. This tissue progressively thickens, and new bone formation is also observed. Residual cyst cavities may also be seen with no evidence of enhancing tissue, thus requiring further treatment. Uncomplicated lesions are diagnosed easily on MRI. Lesions complicated by pathologic fractures may reveal areas of heterogeneous signal and irregular enhancement patterns after the administration of IV contrast.


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Articles

Case History: 20-year-old female with mild pain in left knee joint area, no history of injury and laboratory test was normal for inflammation or rheumatoid.

Unicameral Bone Cyst

A 58-year-old male admitted to our institution with chief complaint of intermittent mild pain in his left knee. He first noticed the pain several years ago without worsening overtime. He reported no correlation between the pain and his daily physical activity. He denied any previous remarkable trauma to the knee. Clinical examination was unremarkable compared to the right side, as no swelling, tenderness, skin color change, motion limitation or palpable mass was noticed.

 Lateral radiograph of the knee revealed a juxta-articular soft-tissue mass located posteriorly to the patellar tendon, displacing the fat pad anteriorly. The mass seemed to be homogenous in nature, well-defined with some amorphous calcified foci inside. Mild degeneration of the left knee joint was also noted. No evidence of osteolysis, bony erosion or periosteal reaction.

On ultrasound, the mass appeared to be solid, well-defined, heterogeneously hypoechoic with posterior enhancement. Multiple calcified foci distributed peripherally with acoustic shadowing were also seen. No evidence of hypervascularity. The anterior patellar tendon was preserved.

 MRI examination of the knee revealed a well-defined extraosseous mass along the anterolateral aspect of the proximal tibia. The lesion was in contact with the underlying bone without cortical breach or bony discontinuity, but causing displacement of the anterior fat pad without involvement to the patellar tendon. No evidence of joint effusion was present. The adjacent tendons and ligaments were normal with preserved fat planes. The mass was isointense to the muscle on T1W images and hyperintense on T2W images. There were some hypointense foci seen on both T1 and T2 images represent calcification proved on plain radiographs. After Gadolinium administration, the mass showed heterogeneously strong enhancement. MRI confirmed the extraosseous, extrasynovial location of the lesion. Various differential diagnoses were accounted for, including extraskeletal chondroma, extraskeletal osteochondroma, soft tissue chondrosarcoma, periosteal chondroma and periosteal chondromyxoid fibroma.

Surgical excision of the lesion was performed. The mass was entirely extraskeletal, extra-articular and extrasynovial with a well-defined capsule. Gross specimen was a 3x2x3cm mass with smooth margins and the cross-section was white and shiny. Histopathological study confirmed benign chondroma.

 Chondromas are generally classified as enchondroma, periosteal chondroma and extraskeletal chondroma according to their location, in which enchondroma is the most common and the rest are rare. These lesions are benign cartilage neoplasms and share the same basic pathology. Extraskeletal chondroma occurs mostly around hands and toes. The lesion can be found at any age, however it occurs more often in adults mainly from ages 30-60, and rare in children with only a few case reports in the literature.

 Meanwhile, juxtacortical chondroma, also called periosteal chondroma, most commonly encounters in the diametaphyses of long bones in children and young adults.

The typical clinical presentation of an extraskeletal chondroma is a painless, slow enlargement nodular soft tissue mass that may be present for a long time prior to diagnosis. On conventional radiography, the lesion may appear as a well-circumscribed, lobulated mass with dense central mineralization. Calcification is usually ring-like, punctuate or granular suggesting the presence of hyaline cartilage. The differential diagnosis of soft tissue tumors with calcification includes several entities, such as hemangioma, tumoral calcinosis, myositis ossificans, extraskeletal chondroma/osteochondroma or soft tissue chondrosarcoma, extraskeletal myxoid chondrosarcoma and synovial sarcoma.

 CT can confirm the extraskeleatal location of the mass and show foci of calcification or ossification that can direct the diagnosis towards extraskeletal chondroma. MRI helps delineate the lesion location and margins, but the appearance is nonspecific. Extraskeletal chondroma have been described as showing low to intermediate signal intensity on T1W images and heterogeneous intermediate to hyperintense signal from the cartilages on T2W images. Contrast enhanced MRI often shows diffuse enhancement within the mass. Marginal surgical excision is usually the treatment of choice with preservation of adjacent bone and soft tissue structures.

 The diagnosis should be confirmed after correlating clinical, radiological and histopathological examination in order to avoid unnecessary, aggressive management.


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4. Miller SF. Imaging features of juxtacortical chondroma in children. 

Case History: 58-year-old male with intermittent mild pain in left knee. No previous remarkable trauma; no correlation between pain and physical activity.

Extraskeletal Chondroma

 A 12-year-old girl admitted to our hospital for dysuria. Physical examination was unremarkable. Urianalysis was suggestive of lower urinary tract infection. Urinary ultrasound was indicated.

Bladder ultrasound showed a fluid-filled cystic intravesical mass contiguous with a mildly dilated left ureter and arised from a normally positioned ureteral orifice (arrow). The wall of the mass also showed continuity with the bladder wall. These findings were consistent with an orthotopic ureterocele. Intravenous urography (IVU) was then indicated.

IVU demonstrated the sign of “cobra head” within the bladder consistent with single system ureterocele. Mild hydroureteronephrosis was also noted. Bilateral renal function remained intact with normal bladder emptying. No vesicoureteral reflux was seen. Left ureterocele was confirmed on cystoscopy.

 Ureteroceles occur in approximately 1 in every 4,000 children. Females are affected 4-7 times more often than males. A slight left-sided preponderance appears to exist, and approximately 10% of ureteroceles are bilateral. In the adult population, ureteroceles also occur more frequently in females.

Orthotopic ureteroceles occur in 17-35% of cases, with an incidence of ectopic ureteroceles of approximately 80% in most pediatric series [1]. Similarly, approximately 80% of ureteroceles are associated with the upper pole moiety of a duplex system [2]. This congenital defect is the obstruction of the meatus, and ureterocele is simply a hyperplastic response to this obstruction. The outer wall is composed of bladder epithelium and the inner wall of ureteral epithelium, with connective tissue and muscle fiber in between [3].

Stephens and colleagues classified ureteroceles as stenotic ureteroceles and ureteroceles associated with duplex ureters. Stenotic ureterocele is the most common type in single ureter system, occurring more often in adults and always intravesical [2].

Urinary tract infection is the most common clinical manifestation. Surgical therapy for both pediatric and adult ureteroceles may include endoscopic puncture, incision or transurethral unroofing of the ureterocele, upper pole heminephrectomy, excision of ureterocele and ureteral reimplantation, and nephroureterectomy. Indications for surgical treatment for ureteroceles depend on the site of the ureterocele, the clinical situation, associated renal anomalies, and the size of the ureterocele. Observation alone is rarely a good option in symptomatic ureteroceles [1].


1. Cooper C.S, Kim E.D, Ureterocele treatment and mangement, Medscape, 

http://emedicine.medscape.com/article/451105-treatment#a1127

.
2. Berrocal et al, Anomalies of the distal ureter, bladder and urethra in children: Embryologic, Radiologic and Pathologic features. Radiographics 2002; 22: 1139-1164
3. Shamsa A. et al, Bilateral simple orthotopic ureteroceles with bilateral stones in an adult, a case report and review of the literature. Urology Journal 2010; 7 (3).

Le Trong Binh, MD
Department of Radiology
Hue University College of Medicine and Pharmacy, Hue, Vietnam

Case History: A 12-year-old girl admitted to our hospital for dysuria. Physical examination was unremarkable. Urianalysis was suggestive of lower urinary tract infection. Urinary ultrasound was indicated.

Orthotopic Ureterocele

 A 57-year-old woman presented complaining of a long lasting epigastric pain. The pain was irregular, vague without spreading or progression or correlation to alimentary habit. She had no nausea or vomiting, neither hematemesis nor hematochezia. She did not report any change in her bowel habit and had not experienced any recent fevers. She denied any history of alcohol consumption, cigarette smoking, non-steroid anti-inflammatory medications intake and weight loss. Her past medical history and previous routine abdominal ultrasound check were unremarkable.

On physical examination, her heart rate, blood pressure, respiratory rate and body temperature were normal. The cardiovascular and respiratory findings are unremarkable. There is little to no tenderness to palpation in the upper abdomen. Neither bowel distension nor abnormal motility was noticed. Auscultation of bowel sound revealed normal. General blood and urine tests were in normal range. Abdominal ultrasound and CT scan findings showed an intramural gastric tumor, which is very suggestive of GIST. A subtotal gastrectomy was performed and the diagnosis of low-grade GIST was confirmed (CD117 +, CD34+, Desmin -). The patient is currently undergoing surveillance.

 Abdominal ultrasound showed a homogenous hypoechogenic mass located within the posterior gastric wall, protruding into the inner lumen. The mass was oval in shape, had regular and distinct margin without infiltration. There was no gastric wall thickening and the layers remained intact. No evidence of hypervascularity on Color Doppler ultrasound of the mass.

 Gastric endoscopy: a submucosal mass was found in the gastric antrum which is ovoid in shape, smooth protruding into the lumen. The mucosal layer remained intact. The mass was relatively firm on compression.

 Axial contrast-enhanced computed tomography (CECT) showed a well-defined, ovoid, homogeneous, intramural mass arising from the gastric antrum with slightly enhancement. The mass was measured 2 cm in diameter. There was no evidence of adjacent tissue infiltration or lymphadenopathy or ascites. CT scan findings were suggestive of a gastric GIST.

 Gross section showed a submucosal tumor located in the pyloric antrum which is firm and fleshy in nature. The mucosal surface remained intact.

  Histopathology HE staining x 400. Tumor cells are fusiform in shape, with vacuolated cytoplasm and arrayed palisade.

  Immunohistochemical staining x 400. CD117+, brown-yellow membrane staining.

 Gastrointestinal stromal tumors (GISTs) are currently the most common mesenchymal tumors of the gastrointestinal tract, with an estimated 4500-6000 new cases reported each year in the United States. The incidence of GIST is estimated to be approximately 10-20 cases/million/year. Malignant possibility is 20 percent to 30 percent. A few estimates and studies indicate the incidences of approximately 14.5 cases/million/year in Sweden, 14.2 in Northern Italy, 13.7 in Taiwan, 12.7 in Holland, 11 in Iceland and 6.5 in Norway. Recent report shows an incidence of 6.8/million from 1992-2000 in the United States [2]. However, the precise incidence of GISTs is still unknown because of the incomplete definition and classification. Over 90 percent of GISTs occur in adults over 40 years old, in a median age of 63, though GISTs have been reported in all ages, including children. No difference in prevalence between sexes. There are no elements that indicate any association with geographic location, ethnicity, race or occupation [3].

Clinical manifestation of GIST is erratic. Seventy percent are symptomatic at presentation, 20 percent are asymptomatic and 10 percent are detected at autopsy. Common presentations include vague abdominal pain, palpable mass, gastrointestinal bleeding, fever, anorexia, weight loss and anemia [1].

Ultrasound may identify GISTs fortuitously, especially if they are large, so that other imaging tests can be performed to confirm the diagnosis. Echoendoscopy can be used to study the esophagus, gastric or rectal tumors to determine local extension. During this procedure, cytopuncture or biopsy can be performed [5]. Computed tomography (CT) is frequently the imaging technique used in the first intention in case of suspected GISTs and CT is also the standard imaging method in patients with GISTs. CT has a high reliability in tumor detection and staging and has been established as the standard method for assessing therapy response. Indeed, CT is considered to be the reference examination for the local study of these tumors and for tumors extension. GISTs usually present as well circumscribed exoluminal masses of different size.

Although surgical resection is the treatment of choice for the primary GISTs, recurrence occurs in most patients, even after a complete resection with tumor-free margin. The median time to recurrence after operation is approximately two years. The main goal of imaging is surveillance to detect recurrence of progression as early as possible. Recurrences typically occur first in the liver of peritoneum. Traditional criteria for progression include tumor size increase, development of new lesions and metastasis [4]. Imatinib and sunitinib were found to be able to potently inhibit the tyrosine kynase activity of KIT [8]. The specific identification of GIST has become more important after the availability of Kit-selective tyrosine kinase inhibitor Glivec, especially in the treatment of high risk, unresectable and metastatic tumors.


1. Roy et al. Spontaneous perforation of jejuna Gastrointestinal Stromal Tumour (GIST). Case report and review of literature, 

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2. Xiaohui Zhao, Changjun Yue. Gastrointestinal Stromal Tumor, 

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3. Stamatakos et al. Gastrointestinal Stromal Tumour: review. World Journal of Surgical Oncology 2009, 7:61.
4. Xie Hong, Haesun Choi, Evelyne M. Loyer, Robert S. Benjamin, Johnathan C. Trent, Chusilp Charnsangavej. Gastrointestinal stromal tumor: role of CT in diagnosis and in response evaluation and surveillance after treatment with Imatinib, 

 2006, 26 (2): 481-495
. 5. Bensimhon D. et al. Imaging of Gastrointestinal Stromal Tumors. 

 2009; 90: 469-480, Elsevier Masson
6. Christopher B. Tan et al. Gastrointestinal Stromal Tumors: a review of case reports, diagnosis, treatment, and future directions. 

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7. Stattaus J. Consensus report on the radiological management of patients with Gastrointestinal Stromal Tumors: recommendation of the German GIST imaging work up. 

2012 (12), 126-135
8. Lamba et al. Recent advances and novel agents for Gastrointestinal Stromal Tumors. 

Case History: A 57-year-old woman presented complaining of a long lasting epigastric pain. The pain was irregular, vague without spreading or progression or correlation to alimentary habit.

Le Trong Binh, MD

Articles

Unicameral Bone Cyst

Extraskeletal Chondroma

Orthotopic Ureterocele

Gastrointesitinal Stromal Tumor