Radiology Grand Rounds-XV

Here is a case of An Unusual Pleural Tumour for the Radiology Grand Rounds submitted by Dr MGK Murthy of Teleradiology Providers. Concept of the Radiology Grand Rounds is available at- Radiology Grand Rounds.

An Unusual Pleural tumour. Dr Jaya, NMC Sky Imaging center, LLRM Medical College, Meerut, Dr(col) M G K Murthy,Dr Sumer Sethi.
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INTRODUCTION:

Many neoplastic tumors exhibit paraneoplastic syndromes manifested by endocrinopathy. This is particularly true of intrathoracic tumors such as lung cancers, thymomas, carcinoid tumors and mediastinal germ cell neoplasms. Solitary fibrous tumors (SFT) of the pleura are rare tumors with unpredictable clinical behavior. SFTs of the pleura previously reported as ‘localized benign mesotheliomas’ have been known to be associated with symptomatic hypoglycemia.1 Localized fibrous mesolitheliomas have been known by other names such as solitary mesotheliomas, submesothelial fibromas and pleural fibromas2; due to controversial nature of origin of the tumor. To evade the discussion about histogenesis, the name ‘solitary fibrous tumor’ is used 2,3.

CASE REPORT:
A 56-year normotensive, nonsmoker male presented with recurrent syncopal attacks, light-headedness and generalized weakness, usually upon awakening or about 4-5 hours after his last meal. He had no history of cough, breathlessness or chest pain. Clinical examination revealed grade 1 clubbing. Chest examination revealed dullness to percussion with decreased breath sounds over the lower half of right hemithorax. Post Prandial Blood sugar level was 75 mg %, C-peptide level was 0.71 mg%; serum insulin level was 4.11mIU/ml (normal fasting level 5-20mIU/ml). Chest X-ray showed a large homogeneous opacity occupying the mid and lower zones of right hemithorax. Right lower lobe showed evidence of collapse and rest of the lungfields didi not show any abnormality. Ultrasound examination showed a well defined rounded mixed echogenic mass in the lower half of right hemithorax above the dome of right hemidiaphragm with minimal right pleural effusion. Subsequent CT examination revealed a large mildly enhancing right pleural mass of solid consistencey with a few areas of hypodense nonenhancing regions suggestive of necrosis. CT value ranged from 20 to 60 HU. No evidence of ribdestruction/brochus cutoff or any mediastinal lymphadenopathy demonstrated. No calcification was seen. Minimal pleural effusion was suggested. Lower lobe all segments showed evidence of collapse. Rest of the lung fields showed no significant abnormality. Radiologically a primary pleural based neoplasm was suggested possibly mesothelioma. FNAC was inconclusive. Metastatic workup showed no abnormality.
Right posterolateral thoracotomy was performed. A large lobulated mass, occupying the posterior and inferior portions of the lower half of right hemithorax was present. The tumor was found to originate from the visceral pleura in the right supradiaphragmatic location. There were no attachments of the tumor to the lung, chest wall or diaphragm. The resected mass measured 19x12x11cm and weighed 4 kilograms. Cut section of the mass showed nodular pattern with large whorled white areas. Histopathological examination showed extensive collagen formation and spindle-like cells with rare mitosis. The spindle cells were arranged in single file pattern, ill defined fasicle with myxoid change and in “patternless pattern”. These findings were consistent with the diagnosis of solitary fibrous tumor of pleura. The postoperative course was uneventful. Blood sugar levels returned to normal after surgery.
DISCUSSION-
The First SFT was described by Wagner4 in his article “Das Tuberkelahnliche Lymphadenom.” In 1931, Klemperer and Rabin5 discovered a diffuse type of tumor that arose from the mesothelial layer from a localized form that arose from the submesothelial connective tissue. In 1952 Clagett et al6 used the term localized fibrous mesothelioma to distinguish these usually benign tumors from the more common asbestos related, malignant mesothelioma. Solitary fibrous tumors (SFTs) represent less than 5% of all neoplasms involving the pleura. SFTs are spindle cell neoplasms. They are usually benign, but may be malignant. In the thorax, they usually involve the pleura, but can be intrapulmonary or mediastinal. Histologically, they show a variety of arrangements, from a “patternless pattern” to a hemangiopericytoma-like or diffuse sclerosing appearance, and stain positive for CD34 and vimentin 7.
Most solitary fibrous pleural tumors cause minimal symptoms despite growth to huge proportions8. When present, the most common symptoms are cough, chest pain, dyspnea and pulmonary osteoarthropathy. Hypoglycemia is rare 9,10. Rarely fibrous pleural tumors are malignant and recur locally or at a metastatic site. Most neoplasms associated with hypoglycemia are pancreatic β-cell tumors. Doege11 reported the first patient with an intrathoracic fibrous tumor associated with hypoglycemia in 1930 (Doege Potter syndrome). In 1981, Briselli reviewed 360 cases of solitary pleural fibrous tumors reported since 1942. Four percent had symptomatic hypoglycemia12; one instance of hypoglycemic coma was fatal 13.
Several mechanisms for hypoglycemia associated with solitary fibrous tumors have been proposed; these include secretion of insulin-like growth factor II (IGF-II or big IGF-II), increased utilization of glucose by the huge tumor, insulin receptor proliferation mediated by the solitary fibrous tumor, decreased gluconeogenesis, and decrease ineffective glucagon secretion. Secretion of IGF by the tumor is the most widely accepted mechanism for hypoglycemia in fibrous masses14, 15. The finding of increased IGF-II with hypoglycemia before resection and decreased IGF-II with abatement of hypoglycemia after resection16, supports this hypothesis.
Our patient had hypoinsulinemic hypoglycemia. After resection the blood sugar and the insulin levels returned to normal. There is an overexpression of IGF II, which is responsible for hypoglycemia in solitary fibrous tumors 17.
In conclusion when confronted with a patient with hypoglycemia and suppressed insulin levels, non-islet cell hypoglycemia should be considered. The case reported here demonstrated that a solitary fibrous pleural tumor should be considered in the differential diagnosis. This case is reported in view of its extreme rarity.