DISCUSSION
Schwannoma and neurofibroma arise from peripheral nerves. Schwannoma
usually occurs in head, neck, retroperitoneum, extremities and
mediastinum.9 Tracheal schwannoma is rare and was
first reported by Straus et.al in 195110 and is
believed to originate from nerves inside the tracheal
wall.2 Schwannoma is common in adults with female
predilection.4 It is frequently found in the lower
third of the trachea followed by proximal trachea and middle third of
trachea.11
Symptoms are misleading in these patients as clinicians mistake dyspnea,
wheezing or cough caused by tracheal neoplasm for symptoms of COPD which
causes delay in diagnosis of 10-15 months in
average.12 Hemoptysis is uncommon symptom for
schwannoma and is predominantly found in squamous cell
carcinoma.6
In spirometry, characteristic flow-volume loop with flattened
inspiratory and expiratory limbs is suggestive of fixed upper airway
obstruction.13 CT scan in Schwannoma demonstrates
well-demarcated, low density mass prior to contrast and contrast
enhancement after injection of the contrast. CT is essential as it helps
to define the location of tumor and allows assessment of luminal and
extrinsic extent of tumor.5 Bronchoscopic evaluation
is indispensable in the localization of the tumor in relation to cricoid
and carina, to determine the length of the luminal disease, assessment
of distal bronchial tree and biopsy of the tumor as well. Assessment of
vocal cord function is important as thyroid carcinoma associated with
tracheal invasion is seen in about 6% of patients presenting for
resection and anastomosis.14 MRI shows isointensity or
hypointensity on T1 weighted images and hyperintensity
on T2 weighted images with heterogenous
enhancement.12
According to Kashara et.al15 pulmonary neurilemmomas
can be divided into two types a) Central type b) Peripheral type. In
terms of relationship between tumor and tracheal luminal space, central
type is further classified into two subtypes 1) Intraluminal type- tumor
is confined in the intraluminal space 2) Transmural type- tumor occurs
in both intraluminal space and extraluminal space(combined type). We
encountered a transmural type of tracheal schwannoma with extraluminal
component contiguous to the left thyroid lobe.
Treatment of tracheal schwannoma can either be endoscopic resection or
surgical resection based on size, location and extent of the tumor.
Endoscopic treatment does not always achieve or confirm complete
resection and is applicable in patients with pedicled and intraluminal
type tumor, patients with advanced age, limited life expectancy, with
severe co-morbidity and in whom complete resection cannot be
offered.16 Complete resection of tracheal schwannoma
with bronchoscopic technique has been reported17 but
one should always look out for local recurrence. Local destruction of
tumor by core out, Nd:YAG laser ablation, cryotherapy and primary
radiotherapy by external beam can be used in addition or as as
alternative to endoscopic resection as a tool to relieve the airway
obstruction caused by tracheal neoplasm.9,11,15,16Surgical resection and anastomosis has been the optimal management where
tumors are sessile and broad based, transmural type tumor, in patients
with preserved cardio-pulmonary function and in recurrent schwannoma.9,16