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Sternal Mass in an 11-Year-Old Boy

1998; Lippincott Williams & Wilkins; Volume: 353; Linguagem: Inglês

10.1097/00003086-199808000-00030

1528-1132

R. A. Hall, David A. Spiegel, John P. Dormans, James S. Meyer, Laura S. Finn,

Histiocytic Disorders and Treatments

An 11-year-old boy presented with an asymptomatic chest wall mass. There was no history of trauma, and he did not report having any fever or chills, dyspnea, weight loss, or other symptoms. His medical history was unremarkable. Physical examination identified a firm, mildly tender fullness in the region of the manubrium. There was no fluctuance, and the mass was not pulsatile. No other visible or palpable lesions were identified in the trunk or extremities. Laboratory studies included a normal complete blood count and sedimentation rate. Radiographs (Fig 1) and computed tomography (CT) scans (Figs 2, 3) were done.Fig 1: Coned down lateral radiograph of the sternum.Fig 2: Axial CT image of the sternum windowed for soft tissue detail.Fig 3: Computed tomography image of the sternum windowed for bony detail at a slightly lower level thanFigure 2.Based on the history, physical findings, and imaging studies, what is the differential diagnosis? RADIOGRAPHIC INTERPRETATION A coned down lateral radiograph showed a lytic lesion expanding the manubrium (Fig 1). Axial computed tomography(Fig 2), windowed for soft tissue detail, revealed a soft tissue density lesion with a small central focus of calcification and areas of cortical disruption involving the manubrium. Bone window images revealed a lobulated internal countour of the manubrium caused by endosteal erosion of the cortex (Fig 3). DIFFERENTIAL DIAGNOSIS Aneurysmal bone cyst Langerhans cell histiocytosis Chondrosarcoma Enchondroma Lymphoma Ewing's sarcoma Giant cell tumor of bone Based on the clinical examination and these imaging studies, biopsy of the lesion was planned. Selective internal mammary arteriography was performed to evaluate the vascularity of the tumor. This study revealed a hypovascular lesion, and several coils were placed in anticipation of the surgical management. Biopsy then was performed (Figs 4, 5).Fig 4: Low power photomicrograph of the biopsy specimen. (Stain, hematoxylin and eosin; original magnification,×32).Fig 5: High power photomicrograph of the biopsy specimen. (Stain, hematoxylin and eosin; original magnification,×320).Based on the history, physical findings, radiographic studies, and histologic picture, what is the diagnosis and how should this patient be treated? See page 260 for the diagnosis and treatment of the lesion. Continuation of ORP Conference from page 259. HISTOLOGY The tumor had a distinctive multilobular growth pattern and was composed of islands of cartilage separated by hypocellular collagen fibers (arrows) with minimal ossification (Fig 4). The nodules contained mature, hypocellular hyaline cartilage with relatively evenly spaced chondrocytes that were typically single within their lacuna. Mitoses or atypical nuclear features were not observed (Fig 5). No invasion of the surrounding bone was evident. DIAGNOSIS Enchondroma of the sternum TREATMENT AND DISCUSSION Primary tumors involving the sternum are extremely uncommon, and most reported cases have been in adults.1-6,10-14,16-22 Benign lesions have been observed less commonly than malignant lesions, although this may reflect the tendency for involvement in an older population. Histologic diagnoses for benign lesions have included enchondroma,4,6,10,11,13,17,19 osteochondroma,1,4,5,7 hemangioma,2 aneurysmal bone cyst,12 neurofibroma,21 eosinophilic granuloma,16 giant cell tumor,12,18 nonossifying fibroma,10 and chondromyxoid fibroma,22 whereas histologic diagnoses for malignant lesions have included chondrosarcoma,1,3,4,5,16-19,21 osteosarcoma,3,10,18,21 reticulum cell sarcoma,1 plasmacytoma,4,5,18,19 Ewing's sarcoma,18 clear cell sarcoma,21 Hodgkin's lymphoma,18,23 and hemangiopericytoma.23 Metastatic carcinoma infrequently may involve the sternum,10,14,21 and tumor simulators may include syphilis, osteomyelitis, and chronic inflammation.1,10 Most studies have suggested that nearly all sternal tumors are malignant, and that a significant percentage are cartilaginous. Pascuzzi et al18 found 18 sternal lesions in 2000 primary bone tumors, of which only one was benign. Dahlin3 reviewed 3987 primary bone tumors and found that 25 of 26 sternal lesions were malignant. Ochsner et al16 evaluated 134 tumors of the thoracic skeleton and found seven sternal lesions of which one was benign. The average age of patients in the series with benign lesions was 26 years, in contrast to the average age of patients with primary malignancies which was 41 years and the average age of patients with metastases which was 56 years. Only 11% of patients with bony or cartilaginous lesions had pain versus 63% of patients with hematopoietic or reticuloendothelial tumors. In a study of chest wall tumors in infants and children, Franken et al7 described a patient with a single sternal osteochondroma with tracheal compression. The sternum is a very unusual location for an enchondroma, and of 290 primary sternal lesions seen at the Mayo clinic, only one was an enchondroma.23 These lesions represent approximately 11% of bone tumors, and 40% may be observed in the hands and feet.3 Most are diagnosed as incidental findings, although pathologic fracture may occur. Slow growth typically is observed, as seen radiographically. Mineralization within the tumor varies and if minimal may underestimate the size of the lesion. Computed tomography helps to identify subtle calcification in the matrix which may not be evident on plain films. Sternal lesions are difficult to image with plain films, and a coned down lateral is the most informative view. Computed tomography was essential in this case in characterizing the bony anatomy and identifying calcification within the matrix. The available evidence concerning etiology suggests that enchondroma represents a developmental defect rather than a true neoplasm. Milgram15 studied histologic sections and thought that the lesions were derived from proliferating tissues from the growth plate, in which an area of chondrocytes failed to undergo hypertrophy and degeneration and then became sequestered within remodeled bone distal to the physis. These cells then continue to proliferate within the epiphysis, metaphysis, or diaphysis. Such cartilaginous inclusions also may be observed in patients with skeletal dysplasias including achondroplasia. The management of sternal lesions has involved wide resection, and techniques for reconstruction have evolved to help alleviate the paradoxical respiration that occurs after removal of a sternal segment.1-6,10-14,16-22 This approach has led to increased survival and potential cure for primary malignant tumors and to enhanced survival with decreased morbidity for metastatic lesions.11,14 Options for reconstruction include rib strut grafts, fascia lata, marlex mesh, local and distant skin flaps, and combinations of these.2,6,10-14,20-22 In contrast to management of enchondromas in the appendicular skeleton which typically involves observation with curettage and grafting reserved for symptomatic lesions, the few sternal cases reported in the literature all have been managed by wide resection.4,6,10,11,13,17,19 This may reflect the perception that the biologic aggressiveness of axial lesions is greater than that observed in the appendicular skeleton. Gilmer et al8 thought that cartilaginous tumors in the flat bones and the axial skeleton had a worse prognosis, and that "actively growing cartilaginous tumors in these locations will prove ultimately to be a chondrosarcoma in the majority of patients regardless of the initial histologic interpretation." Several aspects of the management of this case deserve mention. Because aneurysmal bone cyst was high on the list of differential diagnoses, preoperative selective internal mammary angiography was performed to assess the vascularity of the tumor and to embolize any feeding vessels.9,12 This technique recently was reported by Green et al,9 and definitive surgical management is suggested within 48 hours of the embolization to avoid maturation of a collateral circulation. The treatment in this case was based on the benign histologic finding and the age of the patient and included curettage with iliac crest bone grafting. Although wide resection has been suggested for sternal lesions of any histologic type, nearly all reported cases have been in adults, and there is insufficient evidence in the literature to substantiate a more radical approach for benign disease in children. The patient is currently asymptomatic without evidence of recurrence on a followup CT scan obtained at 6 months after curettage.