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J Thorac Cardiovasc Surg 2009;137:e25-e27
© 2009 The American Association for Thoracic Surgery

Brief Communication

Intrapulmonary psammomatous melanotic schwannoma

Yee-Fung Lin, MDa, Sheng-Chuan Hsi, MDa, Junn-Liang Chang, PhDb, Chun-Hsiung Huang, MDa,*

a Division of Thoracic Surgery, Department of Surgery, Armed Forces Tao-Yuan General Hospital, Taiwan, Republic of China
b Department of Pathology and Laboratory Medication, Armed Forces Tao-Yuan General Hospital, Taiwan, Republic of China

Received for publication April 15, 2008; accepted for publication June 10, 2008.

* Address for reprints: Chun-Hsiung Huang, MD, Division of Thoracic Surgery, Department of Surgery, Armed Forces Tao-Yuan General Hospital, No. 168, Jhongsing Road, Longtan Township, Taoyuan County 325, Taiwan, Republic of China. (Email: qbraintw{at}yahoo.com.tw).

Intrapulmonary psammomatous melanotic schwannoma is rare: Only 1 case has been reported in the English literature.1Go Intrathoracic schwannoma is more common in adults2,3Go and should be differentiated from melanotic schwannoma in young patients. We present a case of primary psammomatous melanotic schwannoma originating in the pulmonary parenchyma and discuss the possible clinical and pathologic associations in the present literature.

Clinical Summary

A 15-year-old girl who was a nonsmoker was admitted because of the incidental finding of a lung mass on a chest x-ray for scoliosis (Figure 1, A ). On admission (Ward of Thoracic Surgery Division of Thoracic Surgery, Department of Surgery), she was asymptomatic and there were no skin pigmentation abnormalities. A series of laboratory examinations, including tumor marker, showed normal results. A chest roentgenogram and contrast-enhanced computed tomography scan showed a well-circumscribed mass approximately 7.0 x 6.0 cm with fat and calcified density in the right upper lobe adjacent to the bronchus (Figure 1, B). Because the tumor was larger than 3.0 cm in diameter and had an intrapulmonary location, it had to be distinguished from lung cancer.


Figure 1
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  		Figure 1. A, Chest x-ray showing scoliosis and a round mass at the right upper lobe. B, Computed tomography scan showing a lobulated mass with soft tissue, fat, and calcified density attached to the bronchus (white arrows).

 
On day 3 after the patient's admission, we performed a right posterolateral thoracotomy via the fourth intercostal space with the patient under general anesthesia. Initially, we attempted to enucleate the tumor. The tumor adhered to the bronchus; it was difficult to detach them from each other so enucleation was converted to a lobectomy. The procedures were changed to prevent the recurrence of a residual tumor from an incomplete initial resection. We dissected the superior pulmonary vein and the superior trunk of the pulmonary artery followed by ligation. The bronchus of the right upper lobe was exposed adequately and managed with a TA 30-3.5 device (Manufactured by United States Surgical, a division of Tyco Healthcare Group LP, Norwalk, Conn. USA). The right upper lobectomy was performed successfully. The patient was ventilated for 9 hours and recovered uneventfully. She was asymptomatic 5 months after the operation.

The submitted lung mass specimen measured 8.0 x 6.0 x 4.0 cm, weighed 50.0 g, and was attached to the sub-bronchial tress with gray brown in color. The tumor sections showed a well-defined encapsulated mass consisting of Antoni A and B areas (Figure 2, A ) with marked myxoid degeneration. Immunohistochemical study presented positive staining for vimentin, S-100 protein, and Masson trichrome, but was negative for glial fibrillary acidic protein, actin, endothelial monocyte antigen, and creatine kinase. There was a marked homogeneous hypercellularity, interspersed melanin pigmentation, and deposition, which was positive for HMB-45 (Melanoma-associated antigen) stain (Figure 2, B). There were numerous psammomatous calcified bodies (Figure 2, C) but no mitotic figures or atypical cells. All of these pathologic findings yielded a definitive diagnosis of psammomatous melanotic schwannoma.


Figure 2
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  		Figure 2. A, Tumor cells are arranged in whorled structures showing Antoni A and B areas (hematoxylin-eosin stain, original magnification x100). The tumor contains intersperse melanin pigmentation (B, black arrows) and numerous psammomatous calcified bodies (C, white arrows) (HMB-45 stain, original magnification x100).

 
Discussion

Psammomatous melanotic schwannoma, a neural sheath-derived tumor, may occur in the central and peripheral nervous systems, although it is most frequently found in the alimentary tract (favoring the stomach) and paraspinal sympathetic chain. It has a series of unusual characteristics that differentiate it from the classic schwannoma: the presence of melanin and psammoma bodies. Melanin-containing schwannoma does not necessarily demonstrate psammoma bodies. Approximately 10% of melanotic schwannomas are malignant, and those with no psammoma bodies may have a malignant change.4,5Go

The differential diagnosis of intrapulmonary melanotic schwannoma includes classic schwannoma and other pigmented lesions. In von Recklinghausen's disease, neurofibromatosis and schwannoma can occur in all areas of the nervous system. Approximately 14% of thoracic neurogenic tumors are associated with Recklinghausen's neurofibromatosis,3Go whereas approximately half of adult cases with malignant tumor are reported. To our knowledge, no patient with psammomatous melanotic schwannoma has had proven von Recklinghausen's neurofibromatosis.

Melanotic schwannomas are readily distinguished from classic schwannomas because the former lack a distinct capsule and clear-cut Antoni A and B areas. Classic schwannoma rarely involves the gastrointestinal tract and lacks melanin, psammoma bodies, and fat. The major clinical difference between the schwannomas is that in more than half the cases, psammomatous melanotic schwannoma is a familial condition associated with Carney's syndrome. Once the syndrome is present, the tumor tends to occur at an earlier age (average age, 22.5 years).5Go

Conclusions

Intrapulmonary neurogenic tumors are essentially amenable to primary surgical therapy, and complete surgical removal alone leads to definite diagnosis and provides therapy. The psammomatous melanotic schwannoma is usually characterized by indolence, and it is not known to have Carney's complex on initial evaluation. Once the pathologic diagnosis was made in the presented patient, we recommended further investigation of both the patient and first-degree relatives for Carney's complex. Complete surgical resection appears to be the optimal therapeutic option, hence there is a reasonably long follow-up of cases that initially were incompletely excised, and evidence of increased aggression.

References

  1. Simansky DA, Aviel-Ronen S, Reder I, Paley M, Refaely Y, Yellin A. Psammomatous melanotic schwannoma: presentation of a rare primary lung tumor. Ann Thorac Surg 2000;70:671-672.[Abstract/Free Full Text]
  2. Takeda S, Miyoshi S, Minami M, Matsuda H. Intrathoracic neurogenic tumors—50 years' experience in a Japanese institution. Eur J Cardiothorac Surg 2004;26:807-812.[Abstract/Free Full Text]
  3. Ribet ME, Cardot GR. Neurogenic tumors of the thorax. Ann Thorac Surg 1994;58:1091-1095.[Abstract/Free Full Text]
  4. Carney JA, Stratakis CA. Epithelioid blue nevus and psammomatous melanotic schwannoma: the unusual pigmented skin tumors of the Carney complex. Semin Diagn Pathol 1998;15:216-224.[Medline]
  5. Carney JA. Psammomatous melanotic schwannoma. A distinctive, heritable tumor with special associations, including cardiac myxoma and the Cushing syndrome. Am J Surg Pathol 1990;14:206-222.[Medline]




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