S Yeluri, A Vaidya, S Karanth, S Maru, S Kapadia, P Ghodgaonkar, M Saxena, D Desai
S Yeluri, A Vaidya, S Karanth, S Maru, S Kapadia, P Ghodgaonkar, M Saxena, D Desai. Mediastinal Lipoma: A Case Report. The Internet Journal of Thoracic and Cardiovascular Surgery. 2002 Volume 5 Number 2.
Mediastinal lipoma[ML] is a rare entity. Though the mediastinum is the most common site of intrathoracic lipoma1, ML constitute less than 1% of all mediastinal tumors2. ML frequently represent an incidental roentgenographic finding. CT Scan is considered the investigation of choice3. CT features of lipoma are quite characteristic. They are clinically significant because ;1] Despite their benign nature, these tumors tend to reach an enormous size and can cause compression on lungs and mediastinal structures and 2] It may not always be possible to differentiate a ML from a liposarcoma on CT or MRI alone4.
Most mediastinal lipoma are discovered incidentally. Although lipoma are the most common benign neoplasm, occurrence within the thoracic cage is uncommon. In contrast to the frequently multiple subcutaneous lipomas, intrathoracic lipoma is usually a single lesion. Multiple intrathoracic lipomas have been reported rarely1.
A 40 year old male presented with a complaint of dull aching,left sided chest pain, dyspnoea on exertion and dry, unproductive cough for a duration of a year.
On examination, patient had a kyphoscoliotic chest with a prominent left sided bulge with widened subcostal angle and an increased anterior posterior diameter with diminished respiratory movement on left. TVF[tactile vocal fremitus] was absent in both the lower zones of chest. On percussion, a stony dull note in the above areas with obliterated traube's area was seen. On auscultation, breath sounds were seen to be absent in the left mammary, inframammary, axillary, infraaxillary and right infraaxillary region with absent vocal resonance in the above mentioned areas. There was no mediastinal shift. Routine haemogram and biochemical investigations were within the normal range.
Chest X-Ray showed an homogenous opacity involving the middle zone and lower zone on both sides with the presence of well defined margins and lobulated margins superiorly.
CT Scan of the chest revealed a large, hypodense mass lesion having extremely low attenuation value[CT density of -80 to -100 HU] in the anterior mediastinum extending on either side upto the posterior thoracic margin and occupying the entire thorax. Significant ventral compression was noted over the superior vena cava, aorta and pulmonary arteries with their posterior displacement. There was marked passive collapse of both lung fields sparing the proximal 1/3rd portion with the presence of small vascular channels.
It was diagnostic of a mediastinal lipoma. Pre-operative respiratory function test [RFT] was suggestive of a severe restrictive disease pattern.
Patient underwent bilateral thoracotomy with transverse sternotomy and a tumor weighing 5.5 kg was excised. Post operative recovery was uneventful with good lung expansion and with clear chest X-Ray. Patient is normal at 6 months, 12 months and 18 months follow up with a normal CT Scan report.
John Politis5 et al from their review of literature have indicated 5 groups of intrathoracic lipoma:1] endobronchial, 2] parenchymal, 3] pleural, 4] mediastinal and 5] cardiac.
Mediastinal lipoma should not be confused with mediastinal lipomatosis which is a condition characterized by accumulation of fat seen with cushing's syndrome or during exogenous administration of corticosteroids.
ML shows a soft tissue density on X-Ray. Though an X-Ray is not adequate, occasionally a clear peripheral zone may be present around the tumor[Heuer' sign]6. In its undifferentiated form, a liposarcoma may be identifiable from a lipoma due to the higher density and better enhancement. But this difference is lost in a well differentiated and encapsulated liposarcoma7. For this reason a complete excision is the diagnostic and therapeutic modality of choice. Where surgery is not contemplated as in small and asymptomatic lesion, a needle biopsy or a thoracoscopic incisional biopsy is necessary. When the report is one of liposarcoma, an excision is essential. A biopsy picture of a lipoma in such a patient may be managed by clinical and chest CT follow up. When attempted, surgical removal of lipoma must be complete due to a tendency to recurrence.
Dr. Sashidhar V. Yeluri, 1, Madhuram Duplex, Near Chanakyapuri Char Rasta, New Sama Road, Baroda-390008,Gujarat, India Phone: 91-98240-43388 Fax: 91-265-780019 E-Mail: Cooldocus@Yahoo.Com, Y.Sashidhar@Mailcity.Com