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Progressive dyspnea in patient with large mediastinal mass
© Fukuhara et al.; licensee BioMed Central Ltd. 2014
Received: 12 August 2013
Accepted: 2 January 2014
Published: 6 January 2014
Liposarcoma occurs very rarely in the mediastinum. Patients often remain asymptomatic until it grows large enough to cause direct invasion or compression of adjacent organs. We report a case of a 77-year-old male presented with dyspnea of exertion and was found to have a large mediastinal mass which was eventually diagnosed as primary mediastinal well-differentiated liposarcoma. The limited respiratory function at the initial presentation prompted phrenic nerve preserving incomplete resection rather than radical removal of the adjacent mediastinal structures. After surgical removal, the recurrence for well-differentiated mediastinal liposarcomas in the mediastinum is unknown; therefore, close follow-up is crucial.
Liposarcoma is the most commonly diagnosed soft tissue sarcoma in adults but occurs very rarely in the mediastinum . The tumors are often asymptomatic until large which causes symptoms from direct invasion or compression of the heart, great vessels or lungs . Gross examination cannot distinguish between lipoma and liposarcoma. In the majority of cases, computed tomography (CT) and/or magnetic resonance imaging (MRI) are sufficient to determine the nature of the tumor [3–6]. The behavior of any liposarcoma is dependent on its histological subtype. The treatment principles are the same as for other soft tissue sarcomas including surgical removal with adjuvant radiation and chemotherapy [7–9]. We herein describe a case of liposarcoma of mediastinum in a 77-year-old man.
Liposarcoma most commonly occurs in the lower extremities and retroperitoneum and rarely in the subcutaneous tissue, paratesticular fat tissue and the mediastinum . Most patients with liposarcomas present complaining of a large mass, often painless unless some sort of trauma has occurred or a vital organ is compressed . Common presenting symptoms of mediastinal liposarcomas are chest pain, dyspnea, wheezing, cough and weight loss . Pericardial and pleural effusions are common, although localized lung collapse is characteristic clinical sign when it reaches larger size . Factors that suggest malignancy are masses greater than 5 cm and lesions that are deep-seated, firm and fixed to underlying structures . Mediastinal liposarcomas are more often found in the anterior mediastinum, adherent to the pericardium and tend to involve the diaphragm and phrenic nerves [11, 12]. Esophagoscopy and bronchoscopy may reveal an extrinsic compression effect of the tumor, but no evidence of an intraluminal lesion. In cases where metastatic disease is suspected a transthoracic CT-guided core-needle biopsy or mediastinoscopy is indicated to obtain tissue specimen to establish the diagnosis .
Findings in plain chest radiography are nonspecific, and offer little except confirming the presence of a soft-tissue mass. CT provides valuable morphologic information and helps in the differentiation of various types of lipomatous tumors [1–6, 10–12]. The typical liposarcoma appearance on CT and MRI is a heterogenic mass composed of adipose tissue mixed with non-adipose components. Radiographic features suggesting higher grade malignancies are large lesion size, presence of thick septations and nodular and/or globular non-adipose mass like areas, and decrease percentage of fat . Well-differentiated liposarcomas are typically composed of more than 75% fat, while the other histologic types usually have less than 25% . Liposarcomas are radiosensitive soft-tissue tumors and the more aggressive tumors demonstrate more radiopacity . Poorly differentiated liposarcomas, particularly the pleomorphic type liposarcoma, may be indistinguishable from other mediastinal malignancies such as malignant fibrous histiocytoma, leiomyosarcoma, desmoids, mesothelial tumors, lymphomas, metastases, and inflammatory masses.
Most common subtype (50% of liposarcomas)
Mature adipocytes with large fatty vacuoles
None of a few lipoblasts
Variable myxomatous tissue with occasional dense hyaline sclerosis
Occasional spindle cells
Low grade with risk of dedifferentiation
Most common type in pediatric age group
Immature mesenchymal giant cells in prominent mucopolysaccharide rich stroma
Lipoblasts with mitotic figures
Prominent vascularization of branching capillaries (chicken wire pattern)
Includes round-cell variant as its high-grade counterpart
Intermediate grade with metastatic risk especially in round-cell variant
Rarest type (5–10% of liposarcomas)
Many lipoblasts with high mitotic rate
Highly anaplastic sarcoma
High grade with high risk of local recurrence and metastasis
May mimic carcinoma or melanoma
Most common with retroperitoneal lesions
High grade with very hight risk of metastasis
While many of the principles governing the evaluation and diagnosis of soft tissue sarcomas certainly apply to liposarcoma, there are features unique for the treatment of anterior mediastinal liposarcoma that deserve special consideration. Particularly important is the tumor proximity to the vital mediastinal organs: heart, aorta, lungs, superior vena cava, phrenic nerves and diaphragm. The current standard of treatment is surgical removal and perioperative adjuvant radiation and chemotherapy [7–9]. Surgical procedures can be intralesional (within the tumor mass, often leaving gross tumor), marginal (through the surrounding fibrous membrane, often leaving microscopic foci of tumor), wide (outside the membrane and compartment, leaving no tumor other than “skip metastases”), and radical (most often involving the entire limb and including the entire compartment in which the tumor was located). In the anterior mediastinum radical and wide resections are frequently unattainable therefore marginal surgery is acceptable for these lesions. The amount of radiation given to a patient may range from 40 to 60 Gy or more, depending on the extent of the surgery, the anatomic site, and likelihood of microscopic or macroscopic retention of diseased tissue . Local control rates of 85–90% have been achieved with combination therapy of surgery and radiation . The role of chemotherapy in the treatment of liposarcoma is controversial. The principal agents are ifosfamide and doxorubicin, both of which are particularly effective for high-grade tumors . When treated with surgery and perioperative radiation therapy, well-differentiated liposarcomas exhibit a < 10% local recurrence rate and a virtually 0% rate of metastasis. In contrast, pleomorphic liposarcomas recur in about 1/3 of cases and spread in about 40%. Five and ten year survival rates for patients with liposarcomas have been reported as 100% and 87% for well-differentiated, 88% and 76% for myxoid variants and 56% and 39% in the pleomorphic subtype [8, 15]. In some patients because of extensive disease, poor clinical status, and comorbidities, despite a favorable pathological diagnosis, no complete curative treatment can be offered. In our patient, we chose to perform marginal resection to spare the phrenic nerves in an attempt to preserve patient’s already compromised respiratory function. Leaving behind microscopic tumor tissue increases the chances of recurrence.
We reported a case with a large mediastinal mass. Our patient had many of the radiological signs for higher grade malignancy: enormous size, multinodularity with thick calcified septation, but his final histocytological diagnosis was well-differentiated liposarcoma, which has a more benign clinical course. After surgical removal, the recurrence for well-differentiated mediastinal liposarcomas in the mediastinum is unknown; therefore, close follow-up is mandatory.
Written informed consent was obtained from the patient for publication of this case report. A copy of written consent is available for review by the Editors-in Chief of this journal.
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