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Neurology India
Medknow Publications on behalf of the Neurological Society of India
ISSN: 0028-3886 EISSN: 1998-4022
Vol. 54, Num. 3, 2006, pp. 322-324

Neurology India, Vol. 54, No. 3, July-September, 2006, pp. 322-324

Letter To Editor

A rare combination of thymic tumor: Radiologically invisible thymolipoma associated with myasthenia gravis

Department of Thoracic Surgery, Baskent University Faculty of Medicine, Adana Teaching and Medical Research Center, Adana
Correspondence Address:Department of Thoracic Surgery, Baskent University Faculty of Medicine, Adana Teaching and Medical Research Center, Adana, Email: dalokay7@yahoo.com

Date of Acceptance: 02-Aug-2006

Code Number: ni06112

Sir,

Thymolipomas are rare benign slow-growing neoplasms.[1] These tumors are usually asymptomatic and are detected incidentally. We have been reported only 28 cases who have MG associated with thymolipoma, including 18 cases English and 10 cases Japanese.[1],[2],[3],[4] Radiological modalities demonstrate the classic combination of fat and soft tissue elements of thymolipomas and establish the tumor attachment to the anatomic region of the thymus.[5] However, small thymolipomas in patients with MG are sometimes not detected. Here, we report a patient with MG who had a thymolipoma that was not detected radiologically. The patient improved within a few months after extended thymectomy.

A 32-year-old woman was admitted to the neurology clinic with a complaint of unilateral ptosis 1 year ago. She also had a 4-month history of mildly proximal muscle weakness and ease of fatigue. Neurological examination revealed ptosis on the left, incomplete abduction of both eyes on lateral gaze, mild facial diplegia, and depressed gag reflex and mild weakness of the proximal muscles of upper extremities bilaterally (Osserman classification type IIA). A prostigmine test was markedly positive. The repetitive stimulation on electromyography was normal, and acetylcholine receptor antibodies were absent. Chest radiography and computed tomography revealed no tumor or other abnormalities [Figure - 1]. Pyridostigmine bromide was started at 180 mg/day and then the doses administered were 360 mg/day for the relief of the symptoms. Treatment with these doses led to a substantial improvement of the symptoms. At the end of the first year, general weakness, especially in the muscles of mastication, neck and shoulders, forced her to consult again. At that moment, electromyographical signs turned to be positive for myasthenia. Titration of acetylcholine receptor antibodies and imaging modalities were not repeated. A decision was taken to perform thymectomy. Three-phase plasma-exchange was performed on the patient, and then she underwent median sternotomy. An extended thymectomy was performed. The thymic and precardial fatty tissue in the region of the left and right phrenic nerves, the diaphragm, and the innominate vein was totally excised. The resected mass of tissue measured 10 x 9 x 2 cm and weighted 56 g. Macroscopic examination of the specimen revealed a 5 x 4 x 2 cm soft, yellow, lobulated mass with a thin capsule. But, the weight of the tumor mass was only 31 g. The histopathological diagnosis was thymolipoma, which consisted of mature fatty tissue and thymic structures, including Hassall′s corpuscles but no germinal centers [Figure - 2]. The symptoms associated with MG gradually improved, and the patient′s medication doses of pyridostigmine bromide were reduced to 120 mg/day after 3 months of follow-up. In the follow-up period 23 months following thymectomy, she was found to be doing well and is still taking anticholinesterase medication at the diminished dose (80 mg/day) without any clear neuromuscular symptoms.

Thymolipoma is an uncommon mediastinal tumor, and association of thymolipoma with MG is rare.[1] Thymolipomas are most frequently diagnosed in the second or third decade of life, whereas the mean age of patients diagnosed with thymolipoma associated with MG is 40-50 years.[1] In contrast, our patient was 32 years old. Thymolipomas are asymptomatic in roughly 50% of cases, and approximately 6% of affected patients have symptoms associated with MG.[1] Most symptoms in patients with thymolipomas are related to compression of adjacent mediastinal organs. Reports in the literature document a wide variation in weight for thymolipomas, ranging from 55 g to 16 kg.[3],[4] Previous studies suggested that thymolipomas associated with MG are smaller than thymolipomas without MG - as in the case of our patient, the tumor weight was 31 g.[1],[3],[4]

Thymolipoma can usually be demonstrated with chest CT and/or magnetic resonance imaging.[5] However, in some patients who have thymolipoma associated with MG, there is no radiological evidence of the tumor. In our case, although thoracic CT showed no mass, extended thymectomy was performed, and pathological examination of the specimen confirmed the diagnosis of thymolipoma. This surgical intervention is the recommended procedure for patients with MG who have a thymic mass, regardless of whether it is radiologically detectable.[2] Similar to previously published cases, our patient′s MG-associated symptoms improved significantly after surgery.

Thymolipomas are not always detected with imaging techniques. In cases of thymolipoma associated with MG, removal of this rare lesion via extended thymectomy can greatly benefit the patients.

References

1.Moran CA, Rosado-de-Christenson M, Suster S. Thymolipoma: Clinicopathologic review of 33 cases. Mod Pathol 1995;8:741-4.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Ozdemir N, Kara M, Dikmen E, Nadir A, Akal M, Yucemen N, et al . Predictors of clinical outcome following extended thymectomy in myasthenia gravis. Eur J Cardiothorac Surg 2003;23:233-7.  Back to cited text no. 2    
3.Rios ZA, Torres LJ, Roca CM, Martinez BE, Parrilla PP. Thymolipomas in association with myasthenia gravis. J Thorac Cardiovasc Surg 2001;122:825-6.  Back to cited text no. 3    
4.Yamamura M, Miyamoto T, Yao H. Thymolipomas with myasthenia gravis in Japan. J Thorac Cardiovasc Surg 2003;125:220-1.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]
5.Strollo DC, Rosado-de-Christenson ML. Tumors of the thymus. J Thorac Imaging 1999;14:152-71.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]

Copyright 2006 - Neurology India


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