pulses, systolic hypertension, exophthalmos) or deficiency Orthopnea or wheezing while supine may be an early sign of a mediastinal mass Failure to thrive or weight loss may also be associated with multiple causes of infection or oncologic illness, including HIV disease, histiocytosis X, mycobacterial infections, and others Likewise, generalized lymphadenopathy in conjunction with fever or rashes may indicate an inflammatory or oncologic process A full examination of the skin is therefore imperative, with special attention to any animal scratches or bites of the face and extremities Suspicion for malignancy increases with changes in the general appearance and color of the child, as with the presence of hepatosplenomegaly or an abdominal mass DIFFERENTIAL DIAGNOSIS Congenital Masses Thyroglossal duct cysts are the most common congenital cyst of the neck, resulting from failure of embryologic thyroglossal duct obliteration prior to hyoid bone formation More than half are diagnosed in children younger than 10 years of age Although 65% of these are found to be infrahyoid, they can develop anywhere in the anterior triangle (along the midline from the base of the tongue to the sternal notch) These may become apparent initially after an upper respiratory infection (URI) or an episode of hemorrhage Masses from thyroglossal duct cysts are classically soft, nontender, smooth, and may move cranially when the child swallows or protrudes the tongue When infected, they may be warm, erythematous, and drain externally If drainage occurs by way of the foramen cecum, there may be an associated foul taste in the mouth Antibiotics (for mouth and skin flora), warm compresses, and incision and drainage (if indicated) should be initiated for signs of infection Complete excision is the treatment of choice after resolution of the acute infection Branchial cleft anomalies most commonly occur from defects in the development of the second branchial arch, giving rise to firm posterior triangle masses (along the anterior border of the sternocleidomastoid muscle near the angle of the mandible) Branchial cleft sinuses present with a pit with or without drainage at the junction of the middle and lower thirds of the sternocleidomastoid muscle Blockage of the sinus tract may cause cysts which are usually fluctuant, mobile, and nontender Conversely, probing or injecting the tract may precipitate an infection, causing warmth and tenderness Consequently, incision and drainage should be avoided because it may result in fistula formation Ultrasonography (US) may be useful in identifying a thin-walled, anechoic, fluid-filled cyst