Pediatric tumors

42 Pediatric tumors






Introduction


Pediatric tumors are highly varied in origin, pathophysiology, and clinical presentation and therefore have different modes of treatment associated with them. This chapter presents tumors that are benign masses but have complex presentations, such as the neurofibromatosis group of tumors that have multiple systemic signs but can be grouped and treated based on their local craniofacial/ophthalmologic complications. Another spectrum of tumors, the juvenile aggressive fibromatosis group, are masses that originate from myofibroblastic tissue and can exhibit a highly aggressive growth pattern. Pediatric masses can also have their origin due to errors along the pathways of embryological development. Tumors such as dermoids present in a continuum of dermoids to encephaloceles. Fusion errors in development can lead to branchial arch pathology, and the presence of embryologic tissue remnants can lead to thyroglossal duct cysts. Pediatric tumors can also be highly malignant, such as the soft-tissue sarcoma group of tumors, including rhabdomyosarcomas, or can be benign masses that have potential for malignant transformation, such as pilomatrixomas. Finally, masses can be present as acute or chronic reactions to infections leading to lympadenopathy.


This chapter attempts to present a spectrum of pathology which varies from chromosomal errors causing aggressively growing lesions, errors during embryogenesis leading to maldevelopment of tissue structures or remnant tissue, malignant transformation of various tissue types, and the effect of infectious pathology on normal tissue.



Neurofibromatosis








Optic nerve gliomas



Diagnosis/patient presentation


Optic nerve gliomas are the most common central nervous system tumors in NF-1 patients. They occur in 15% of cases and are histologically identified as low-grade pilocytic astrocytomas.4,5,8 They are relatively indolent and sometimes asymptomatic. If symptomatic, they can cause proptosis, squint, abnormal color vision, visual field loss, pupillary abnormalities, and hypothalamic dysfunction.7



Treatment/surgical technique


Treatment involves vincristine and cisplatinum.9 Surgery is necessary if proptosis is present, and if there is a need to debulk extensive chiasmal gliomas.




Craniofacial manifestation




Treatment/surgical technique


Treatment is based on Jackson’s classification11,14:



Article I. Class 1: significant soft-tissue involvement with minimal bone involvement and normal vision


image Treatment involves debulking of the soft-tissue component of the tumor through an anterior, lateral, or anterolateral orbitotomy. If blepharoptosis is present, levator resection is performed.16 In cases where only a partial resection is carried out, a technique of netting the remaining tissue using Teflon mesh has been proposed18 (Fig. 42.1).

Article II. Class 2: soft-tissue and bone involvement with normal vision


image Treatment involves an intracranial approach for tumor debulking and posterior orbital wall reconstruction.16 After the tumor is debulked, the herniated temporal lobe is reduced and bone grafts, obtained from splitting the contralateral frontal bone, are used to reconstruct the posterior and superior orbital walls. Orbital volume is increased with osteotomies and the globe is elevated by raising the canthal ligaments and building the floor. A two-stage approach has been suggested in which the intracranial portion of tumor debulking and orbital reconstruction is completed in stage 1. A second-stage procedure is performed in which subcutaneous debulking, eyelid, face, and orbital reconstruction is completed19 (Fig. 42.2).

Article III. Class 3: soft-tissue and bone involvement with blindness or an absent globe






Neurofibromas



Diagnosis/patient presentation


Nerve sheath tumors arise between the dorsal root ganglion and terminal nerve branches.4,5,20 They are composed of Schwann cells, fibroblasts, mast cells, and perineural cells.7,20,21 Localized cutaneous neurofibromas are the most common nerve sheath tumors. They present as multiple slow-growing, pedunculated lesions that progressively increase in prominence.7 These lesions can be surgically excised for symptomatic benefit. This, however, may lead to hypertrophic scarring. The benefits of carbon dioxide laser treatment have not been clearly established. Diffuse cutaneous neurofibromas present as a plaque-like thickening of the dermis and subcutaneous tissue, and are most frequently found in the head and neck region. These are nondestructive, soft, compressible lesions that grow along the fibrous septa in children and young adults. Removal of these subcutaneous lesions may lead to neurological deficits in the region of the concerned nerve. Localized intraneural fibromas are the second most frequent type of neurofibroma, and represent fusiform enlargement of peripheral nerves. These are the most common neurofibromas of the upper extremity, and account for 85% of cases.22 Spinal and cranial nerves may also be involved. Massive soft-tissue neurofibromas (elephantiasis neurofibromatosa) lead to distortion of the face and require complete excision.23 Plexiform neurofibromas are composed of nerve sheath cells proliferating along the length of the nerve and are associated with hypertrophy of the overlying soft tissue, hyperpigmentation, and hypertrichosis of the overlying skin. Plexiform neurofibromas occur in 16–40% of patients with NF. These lesions involve the trunk (43–44%), extremities (15–38%), and head and neck (18–42%).20 They are congenital in origin and become evident by 2 years of age. Plexiform neurofibromas are locally destructive lesions that grow during periods of hormonal change, and may involve multiple nerve branches and plexi.24



Treatment/surgical technique


Preoperative contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI), angiography, and embolization have been recommended.20,21,22,25 The highly vascular nature of these lesions makes surgical removal complicated.24 Multiple nonsurgical management options, such as farnesyl transferase inhibitors, antiangiogenesis drugs, and fibroblast inhibitors, are being explored.26 Tumors resected in children below the age of 10 years recur in 60% of cases, while those resected above the age of 10 years recur in 30% of cases.27



Malignant degeneration of peripheral nerve sheath tumors



Diagnosis/patient presentation


There is an 8–13% lifetime risk for these tumors to undergo malignant degeneration. This occurs predominantly between the ages of 20 and 35.4,7 Medium and large nerves of the thigh, buttock, brachial plexus, and paraspinous areas are involved. Signs of malignant degeneration include increased pain, new neurological deficits, sphincter disturbance, rapid increase in the size of the neurofibroma, or change in texture.28 Fluorodeoxyglucose positron emission tomography helps with the quantification of glucose metabolism in the cells, and can help distinguish between benign and malignant lesions.29,30











Dermoids





Nasal dermoids



Basic science/disease process


Between the third and eighth week of embryogenesis, when the neural groove deepens to form the neural tube, incomplete sequestration of the neuroectoderm from the somatic ectoderm leads to a persistent connection of the foramen cecum with the fonticulus nasofrontalis, and the foramen cecum with the prenasal space. These connections cause the formation of nasal dermoids, dermal sinuses, gliomas, and encephaloceles.41 Nasal dermoids can be present at any point between the glabella and the base of the columella. Intracranial extension can exist via the tract through the nasal septum and foramen cecum, or through the widened frontonasal suture (fonticulus nasofrontalis) and foramen cecum. In these cases, the presence of the dermoid between the leaves of falx and a bifid crista galli are noted (Fig. 42.4).





Treatment/surgical technique


Dermoid cysts or sinuses that are present at the columella usually extend to the nasal spine. Resection involves a circumscribed removal of the sinus tract. If a cyst is associated with it, it is dissected through the labial sulcus. Sinuses and cysts that are present from the radix to the nasal tip, but are without intracranial extension, are excised in combination with an open rhinoplasty approach. This approach has been reported to have improved exposure of the osteotomies, the upper lateral cartilages, and the septum44 (Fig. 42.5). A closed rhinoplasty technique has been proposed for the excision of superficial distal nasal-tip dermoids. Since most nasal dermoid cysts are confined to the superficial nasal area, this technique can prove to be beneficial.45 For lesions with suspected/confirmed intracranial extension, failure to excise the tract completely can lead to abscess formation, meningitis, or osteomyelitis.46,47 Multiple approaches have been proposed.4861 The traditional approach calls for combining an intracranial procedure such as a bifrontal craniotomy, with an extracranial procedure, such as a transverse, vertical, inverted U, lateral rhinotomy, or rhinoplasty to address the entire sinus tract.48,49



A second approach, described as the “keystone” technique, involves a bifrontal craniotomy superior to the supraorbital rims, two paramedian sagittal osteotomies extending down the length of the nasal bones, followed by outfracturing of the keystone component. This technique allows complete exposure of the sinus tract and enhanced exposure of the anterior cranial base.53 A similar subcranial transglabellar approach involves horizontal osteotomies above the suprarorbital rims and at the level of the nasal bones, and vertical osteotomies at the supraorbital rims to expose the intracranial portion of the dermoid. This technique allows one to approach the lesion from one direction, thereby maintaining a single field. It is also attributed to require decreased frontal-lobe retraction and therefore has a lower risk of contusions, cerebral edema, and long-term neurological defects.55 The osteotomy size is smaller than the traditional frontal craniotomy approach, which reduces the risk of dural tears or cerebrospinal fluid leaks58 (Fig. 42.6).




Outcomes, prognosis, and complications


The recurrence rate of nasal dermoids after surgical excision is 12%.61 A meta-analysis showed that the rate of complications with the traditional craniofacial approach was 30% while the subcranial approach reduced the complication rate to 16%.57 Complications included tension pneumocephalus, cerebrospinal fluid leakage, subdural hematoma, longer operative times, and longer intensive care unit stays.58,59




Intradural dermoids and dermal sinus tracts



Basic science/disease process


The incomplete sequestration of neuroectoderm and somatic ectoderm during embryogenesis can lead to persistent dermal sinus tracts from the occiput to the sacrum.62,63 About 1% of these tracts are found in the cervical spine, 10% in the thoracic spine, 41% in the lumbar spine, and 35% in the lumbosacral spine.64 These sinus tracts are cephalically oriented, lined with stratified epithelium, and may lead to the vertebral column, ending as intradural dermoid cysts.62



Diagnosis/patient presentation


Dermal sinus tracts can present as hypertrichosis, skin tags, abnormal pigmentation, subcutaneous lipomas, or angiomata.65,66 The presence of these tracts can also lead to recurrent bacterial meningitis. Additionally, traction on the spinal cord can occur and can lead to symptoms of motor weakness, autonomic irritation, or sphincter dysfunction. MRI is the imaging tool of choice, and helps with the evaluation of other associated pathologies such as inclusion tumors, dermoids, epidermoids, teratomas,6774 split cord malformations75,76 and tethered cords77 (Fig. 42.7).


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Feb 21, 2016 | Posted by in General Surgery | Comments Off on Pediatric tumors

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