Positron emission tomography /CT images showed a moderately increased
18F-FDG uptake in the mass of left lung lower lobe superior segment (SUVmax: 2.71). No pathological
18F-FDG involvement was detected in another region of the whole body scan. The patient underwent tru-cut biopsy. Since histopathological diagnosis could not be made,
thoracotomy was performed.
Schwannomas are the second most common benign peripheral nerve sheath originated
tumor. Due to its development from Schwann cells, it can be seen in all organs or tissues during intracranial, extracranial, or spinal nerve courses where these cells are found.
Schwannomas are extremely rare in the lung, regardless of the patients age. Ohtsuka et al. (2005) stated that in the review of 62 patients with intrapulmonary or bronchial
schwannoma (5-83 years; 28 male, 34 female patients), this
neoplasm constitutes approximately 0.2% of all
pulmonary neoplasms. Although it is usually sporadic and single lesion, it can also be seen with
neurofibromatosis (NF)1 or NF2. Especially in
schwannomatosis cases, NF2 is observed with multiple and benign characters. In patients with
tumors located proximal to the lobar bronchus,
atelectasis or
pneumonia associated with
cough and
dyspnea may occur. However, most patients with peripheral intrapulmonary
schwannoma have no symptoms.
Fluorine-18 FDG-PET/CT is a useful imaging modality to separate malignant
solitary pulmonary nodules from benign nodules. There are few cases of
18F-FDG PET/CT imaging intrapulmonary
schwannoma in the literature. Maximum standard uptake values (SUVmax) of
Schwannomas in
18F-FDG PET/CT are variable. SUVmax values are generally low and moderate, but have been shown to vary between 1.9-7.2. The reason for the variation in SUVmax is thought to be due to varying degrees of cellularity, microvascular density or vascular permeability. Histopathologically, dense cellular areas (Antony A) and more hypocellular areas (Antony B) specific to
Schwannoma appear in varying proportions. Also, the structure formed by spindle schwann cells side-by-side within the fields of Antony (Verocay body) is characteristic. Surgical resection, endoscopic resection and
yttrium aluminum garnet (
YAG) laser resection were used for the treatment of primary intrapulmonary
schwannoma. The contribution of
18F-FDG PET/CT in
schwannoma is that it provides malign and benign distinctions of intrapulmonary masses. However, a cutoff for SUVmax has not been identified in the malignant benign distinction. The diagnosis must be verified histopathologically.