MEDIASTINAL DERMOID IN AN ADULT PRESENTING AS A RESPIRATORY EMERGENCY

MEDIASTINAL DERMOID IN AN ADULT PRESENTING AS A RESPIRATORY EMERGENCY

A HEROOR, HVR REDDY, S VYAS, S SHARMA, RK DESPHANDE
Department of Thoracic and Paediatric Oncology, Tata Memorial Hospital, Dr. E Borges Marg, Parel, Mumbai 400 012.

Teratomas are thought to originate from totipotential embryonic cells that escaped the influence of the organizers during the intrauterine period. This event probably occurs near the primitive streak and therefore, median and paramedian parts are affected. In the mediastinum they constitute about 60% of tumours in adults. They are usually identified on routine chest roentgenology but symptoms of pain or cough may be there. It is extremely rare for an adult to present with respiratory distress due to dermoid. We present a case scenario of young lady with a complex teratoma in the anterior mediastinum, which was secondarily infected and presented with high-grade fever and respiratory distress.

INTRODUCTION

Cystic dermoids are congenital tumours containing derivatives of all germ layers.[1] Their origin is widely accepted to be from the pleuripotent stem cells. They constitute 60% of all mediastinal tumours seen in adults and occur mostly in the anterior mediastinum and very rarely in the posterior mediastinum (3-8%).[2] Usually it will be an incidental observation on routine chest X-ray that leads to clinical diagnosis. It is well known for the dermoids to cause tracheobronchial compression in children. In adults, however, it is extremely rare to cause symptomatic airway obstruction.

CASE REPORT

35-year-old housewife presented to our outpatients department with symptoms of acute dyspnoea, restlessness and high-grade fever. The X-ray chest (Fig. 1) showed a large mediastinal mass with coarse calcific area within it and evidence of right pleural effusion with multiple levels in it. She was admitted with a differential clinical diagnosis of loculated pyopneumothorax or infected hydatid cyst. Transthoracic aspiration yielded about 100 ml of pus, which on culture grew mixed growth of Pseudomonas aeruginosa and Proteus mirabilis. With intensive antibiotic treatment according to the sensitivity, hydration and other supportive treatment, symptoms subsided. The subsequent X-ray chest showed a resolution of the right pleural effusion but the mediastinal shadow persisted. The aspirated material was also sent for cytology which was reported as "differentiated squamous cells with foreign body material? fat? keratin in an acute inflammatory background". The CT chest (Fig. 2) showed rounded hypodense heterogeneous (15.8 x 9.8 x 4.8 cms) variable enhancing lesion in the anterior mediastinum more on the right side. Areas of fat (attenuation of -40 H.U) and calcification (attenuation of +543 H.U) are seen in addition to soft tissue attenuation. The intervening fat plane between the heart and the mass and the bronchus intermedius and the mass are indistinct in places. It was convincing that the infected dermoid cyst was the underlying pathology causing respiratory distress. The Fibreoptic bronchoscopy revealed compressed and inflamed right main and intermediate bronchus. The 2D echo showed a mild RV dilatation, a minimal pericardial effusion and a mass abutting the RV.

She was explored by right anterolateral thoracotomy and noted an intact 20 x 15 cm complex mass, which was inseparable from the pericardium. The right phrenic neurovascular bundle was running over the lateral wall of the mass. There were adhesions from the surrounding lung. With careful dissection, the adhesions from the lung were separated. The phrenic neurovascular bundle had to be sacrificed during the dissection. A small strip of the pericardium was excised along with the cyst and the pericardial defect was closed primarily. The mass contained hair, cheesy material and a solid protuberance (Rokitansky protuberance) having the bony calcification.

The postoperative course was uneventful and has resumed normal activity.

Fig. 1: Chest X-ray showing large mediastinal mass with coarse calcific area
within it and evidence of right pleural effusion with multiple levels in it.

Fig. 2: The CT chest showing rounded hypodense heterogenous - (15.8x9.8x4.8 cms) variable enhancing lesion in the anterior mediastinum more on the right side. Areas of fat (attenuation of -40 H.U) and calcification (attenuation of +543 H.U) are seen in addition to soft tissue attenuation. The intervening fat plane between the heart and the mass and the bronchus intermedius and the mass are indistinct in places.

DISCUSSION

Mediastinal dermoids are well described in medical literature.[3,4] Though they are referred to as "benign teratoma", this term is a misnomer. It is classified as benign but it represents the most differentiated germ cell tumour morphology. The very presence of a mature teratoma implies that a totipotential precursor, embryonal carcinoma gave rise to it.[5] Further malignant differentiation of these adult tissues can occur and is said to be much more frequent in the mediastinum than in any other site.[6-9] Aggressive management of these tumours is required for patients to achieve long-term disease free status.

About two third of the benign teratomas in adults are asymptomatic. Pain is the most common symptom. It can also cause dyspnoea and cough. Rarely it may rupture into the tracheobronchial tree and can cause expectoration of hair - "trichoptysis" and greasy material - sebum. If it ruptures into the pleura, it can cause empyema. Rupture into the pericardium has also been reported[2] causing pericardial effusion and tamponade. However, it is extremely rare for a patient to present to the emergency room with acute onset dyspnoea, high-grade fever and blood-streaked sputum without rupture of the cyst into the pleural or pericardial cavity. The initial diagnosis of such presentations is usually a pyothorax. Thus this was a rare presentation of an uncommon tumour. In this patient initial aspiration of pus that on culture yielded mixed growth of pseudomonas and proteus and the chest X-ray showing calcification raised the possibility of infected hydatid cyst. However CT scan depicted clearly the fat and the calcification, which were consistent with the dermoid. The histopathology showed mature cystic teratoma with solid component.

Most often there are no physical findings in a benign teratoma. Routine roentgenographic examination reveals that the teratoma usually projects into right or left hemi thorax. Calcifications have been reported in one third of patients.[10] Computed tomography reveals the extent of lesion better than a standard X-ray. Prognosis after a complete surgical resection is excellent.

Primary mature mediastinal teratoma can be cured with complete surgical resection.[11] Surgical resection is mandatory for the following reasons:

a) It can grow slowly and can invade adjacent structures (growing teratoma syndrome).[12]

b) It can undergo a malignant transformation.[6-9]

c) Complications such as infection and rupture.

The "growing teratoma syndrome" is when the teratoma invades or compresses the surrounding structures. The malignant transformation is quite often refractory to cisplatin-based chemotherapy and represents a poor prognosis.

Thus surgical management provides definitive management of these tumours. Recurrence after a complete surgical excision is unknown.

REFERENCES

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7.Aliotta PJ, Castillo J, Englander LS, et al. Primary mediastinal Germ cell tumours. Cancer 1988; 62 : 982-84.

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10.General Thoracic Surgery. 3rd ed. Ed Thomas Shields. Lea and Febger. 1989.

11.Lewis BP, Hurt RD, Payne WS, et al. Benign Teratomas of mediastinum. J Thorac Cardiovasc Surg 1983; 86 : 727-37.

12.Logothetis CJ, Samuel ML, Trindade A, et al. The growing teratoma syndrome. Cancer 1982; 50 : 1629-35.

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