 |
       |
|
|
CASE REPORTS
Aberrant Cervical Thymus in Children
Prashant K Adivarekar, Gaurav Baheti, Dharmendra Singh, Sangram Singh
Though uncommon, aberrations in the migration of thymic tissue can occur. We report a case of a 13 year old boy who presented to us with an asymptomatic cervical mass for which he underwent a biopsy, with a preoperative diagnosis of malignancy or tuberculosis, and the biopsy revealed ectopic normal thymic tissue. Despite its rarity, it should be considered in the differential diagnosis of asymptomatic cervical masses in children.
INTRODUCTION
Though uncommon, aberrations in the migration of thymic tissue can occur and there are descriptions of thymic tissue in situations as varied as the base of the skull, and the mediastinum at the tracheal bifurcation. Cervical ectopia would appear to be the most common site,1 along the path of descent (near the carotid sheath, along the anterior border of the sternocleidomastoid, lateral to the thyroid capsule). In a collective review of literature between 1901 and 1987, Nowak et al2 reported only 76 cases of aberrant solid and cystic thymic lesions that presented as cervical masses. We present our experience with a case of an ectopic cervical thymic tissue.
CASE REPORT
A 13 year old boy presented to us with an asymptomatic left lateral neck mass noticed since the past 1 month. On physical examination, it was an ovoid 7 x 6 cms mass which was firm, nontender with an irregular surface, situated lateral to the thyroid gland (Fig. 1).
Chest X-ray was within normal limits. Ultrasound showed a homogeneous, solid mass. The child was explored with the pre-operative diagnosis of malignancy or tuberculosis. At exploration, the patient was found to have multinodular greyish mass deep and anterior to the sternocleidomastoid muscle, adherent to the carotid sheath and extending deep to the hypoglossal nerve. A wedge biopsy was taken. Microscopic examination revealed a normal thymic tissue with lymphocytes and Hassal’s corpuscles.
His post-operative course was uneventful. At 5 months follow-up the patient is asymptomatic with the mass regressing in size.
DISCUSSION
Aberrant cervical thymus is a rarely encountered clinical entity in children. Tovi and Mares3 reported 68 cases in 1978. In a collective review by Nowak et al2 in 1988, among the 91 cases of aberrant thymus, 76 presented as neck masses whereas the remainder were mediastinal in location. Nitsana et al4 in 1990 presented 3 cases of cervical thymic tissue. Cystic lesions were more common in all the series, and in the review of Nowak et al, only 26 solid lesions were found. Cervical thymus seems to occur more often in boys than in girls2 and is more often found on the left side.6
Most of these masses arise as a consequence of migrational defects during thymic embryogenesis. The thymus is a paired organ that is derived from the ventral wing of the third pharyngeal pouch on each side, occasionally receiving contribution from the fourth pouch in the 6th week of foetal life. Each primordium elongates caudally and medially as a tubular structure (thymopharyngeal tract). During the 8th week of foetal life the primordial cells begin to approach each other as they move, caudal to the thyroid. The cephalad portion or the connecting stalk involutes and the bilateral thymic primordia fuse in the midline as they descend behind the sternum into the superior mediastinum, where they lie in contact with the pericardium and the thoracic inlet.3,5,6Because the parathyroid glands are derived from the dorsal wing of the third pharyngeal pouch and descend with the thymus,3,7 the parathyroid gland may be found deeply embedded in the ectopic thymic tissue. Another pathogenetic mechanism includes sequestration of accessory cervical foci of the thymic tissue along the path of normal descent.2
Thymus rarely invades contiguous structures and therefore rarely produces symptoms.3,8Levis6 in his review described a case of infection in a cervical thymus causing tracheal displacement. A case of severe dyspnoea and dysphagia resulting from aberrant cervical thymus was demonstrated by Bistritzer et al.9
Mcleod and Karandy10 reported a case of a 6 week old infant who suffered an acute respiratory arrest secondary to a large, congenital aberrant thymus. There have been reports of a malignant transformation in association with aberrant cervical thymus, as well as one case of myasthenia gravis in a cervical thymoma.6
Although diagnosis of ectopic thymus is rarely made preoperatively, consciousness of this entity with its variety of presentations (inflammatory, neoplastic, congenital) enables the surgeon to more readily identify these lesions and not to perform extensive resection.
REFERENCES
1. Finch DRA, Gouch MH. Ectopic thymic tissue presenting as a lateral cervical swelling. Br J Surg 1972; 59 : 885-6.
2. Nowak PA, Zarbo RJ, Jacobs JR. Aberrant solid cervical thymus. Ear Nose Throat J 1988; 67 : 670-7.
3. Tovi F, Mares AJ. The aberrant cervical thymus-Embryology, pathology and clinical implications. Am J Surg 1978; 136 : 631-7.
4. Nitsana S, Arie LB, Herve B, Pierre R. Aberrant cervical thymus in children. J Pediatr Surg 1990; 25 : 1196-9.
5. Hamilton WJ, Boyd JD, Mossman HW. Human embryology (ed 4). Baltimore, MD, Williams and Wilkins. 1972 : 312-22.
6. Levis MR. Persistence of the thymus in the cervical area. J Pediatr 1962; 61 : 887-93.
7. Moore KL. The developing human-clinically oriented embryology (ed 4). Philadelphia, PA, Saunders. 1988 : 179-84.
8. Malone PS, Fitzgerald RJ. Aberrant thymus: A misleading mediastinal mass. J Pediatr Surg 1987; 22 : 130-1.
9. Bbistritzer T, Tamir A, et al. Severe dyspnea and dysphagia resulting from an aberrant cervical thymus. Eur J Pediatr 1985; 144 : 86-7.
10. McLeod DM, Karandy EJ. Aberrant cervical thymus. A rare cause of respiratory distress. Arch Otolaryngol 1981; 107 : 179-80.
SYSTOLIC BLOOD PRESSURE
It is time to focus on systolic hypertension - especially in older people
Elevation of systolic blood pressure predicts the risk of cardiovascular disease better than increases in diastolic blood pressure. Nevertheless it is the elevation in systolic blood pressure that still limits our ability to control blood pressure to the recommended goal of less than 140/90 mm Hg.
Systolic blood pressure is easier to determine.
Isolated systolic hypertension is defined as a systolic blood presure more than or equal to 140 mm Hg and a diastolic blood pressure less than 90 mm Hg and is the most common form of hypertension. Its prevalence increases with age occurring in two thirds of people 65 years of age and three quarters of those over 75 years of age.
In people aged up to 50, both diastolic blood presure and systolic blood pressure are independently associated with cardiovascular risk. At age 50 systolic blood pressure is far more important than the level of diastolic blood pressure in predicting the risk of coronary heart disease, left ventricular hypertrophy, congestive heart failure, renal failuer and mortality in people with hypertension. At age 60 years, however, as vascular compliance is reduced, an increasing systolic blood pressure and a lower diastolic blood pressure increase cardiovascular risk.
Systolic blood pressure remains more difficult to control than diastolic blood pressure. Nevertheless, doctors should be able to lower systolic blood pressure to less than 140 mm Hg in about 60% of patients. A diuretic and a dihydropyridine calcium antagonist are the only classes of drugs that have been tested as initial treatment in placebo controlled trials on isolated systolic hypertension.
If not used initially, a thiazide diuretic should be included in most regimens to enhance the efficacy of other blood presure lowering agents and reduce the risk of ischaemic stroke. Since two or more agents are often necessary to reach the target of 140 mm Hg, caution should be exercised when lowering diastolic blood pressure to less than 55 mm Hg.
Isolated systolic hypertension remains the most common form of hypertension and the most difficult to treat. Substantial evidence supports the value of treating isolated systolic hypertension, and we must better inform doctors and the public about its consequences. It seems appropriate that we continually focus our efforts on more effective control of systolic blood pressure.
Jan N Basile, BMJ, October, 2002; 325 : 917-18.
 |