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Ann Thorac Surg 2000;70:671-672
© 2000 The Society of Thoracic Surgeons

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Case report

Psammomatous melanotic schwannoma: presentation of a rare primary lung tumor

^a Department of Thoracic Surgery, Sheba Medical Center, Tel Hashomer, Israel
^b Department of Pathology, Sheba Medical Center, Tel Hashomer, Israel

Address reprint requests to Dr Yellin, Department of Thoracic Surgery, Sheba Medical Center, Tel Hashomer, Israel 52621
e-mail: chest18{at}netvision.net.il

	Abstract

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A 30-year-old nonsmoking man underwent a left lower lobectomy with bronchoplasty for an obstructing lesion of the left lower lobe. Pathology results demonstrated a psammomatous melanotic schwannoma, a rare pigmented neural tumor of which only 25 cases have been reported as originating in the respiratory tract.

	Introduction

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In 1990 Carney [1] described a syndrome that includes a unique tumor called psammomatous melanotic schwannoma. Although most of these tumors are benign, some cases of metastases have been reported. This tumor is a rare pigmented neural tumor of which only 25 cases have been reported as originating in the respiratory tract. We report a new case of psammomatous melanotic schwannoma originating in the lung and review the features of this tumor and Carney’s syndrome.

A 30-year-old nonsmoking man was admitted after an acute onset of dyspnea 1 month earlier. Aside from a small cutaneous myxoma excised from his cheek 4 years earlier, he had no history of any other medical condition. A chest roentgenogram demonstrated atelectasis of the left lower lobe. A computed tomography scan showed a lesion obstructing the left lower bronchus. Bronchoscopy revealed a pale red, vascular 1-cm mass obstructing the lower lobe bronchus with extension into the main bronchus. A biopsy was taken and was interpreted as a typical carcinoid.

At thoracotomy a 4-cm black tumor was seen, originating in the lower lobe bronchus and extending 5 mm into the main bronchus. The tumor penetrated the bronchial wall toward the carina. A left lower lobectomy was performed with bronchoplasty of the main bronchus and preservation of the left upper lobe. The postoperative course was characterized by a small peripheral air leak, but after 14 days the patient was discharged.

Microscopically (Fig 1) the tumor occupied the submucosa, dissected through the bronchial wall, and extended into the peribronchial fat tissue. The tumor cells varied from spindle-shaped cells with little cytoplasm to cells with ill-defined cytoplasmic borders. Nuclei were round to oval and displayed vesiculation and prominent nucleoli. Nuclear pleomorphism was mild and no mitotic figures were seen. Tumor cells were arranged in whorls with occasional palisading. Numerous psammoma bodies and coarse granular melanin pigmentation were evident throughout the tumor. (Fig 2)

View larger version (161K): [in this window] [in a new window]   Fig 1. Psammomatous melanotic schwannoma tumor cells are arranged in whorled structures with some degenerative cysts and dilated blood vessels. Note the heavy melanin pigmentation and psammoma bodies (Hematoxylin & eosin; x100).

View larger version (148K): [in this window] [in a new window]   Fig 2. The tumor contains spindle-shaped cells with round to oval nuclei displaying vesiculation and prominent nucleoli. Coarse granular melanin pigmentation and psammoma bodies are present (Hematoxylin & eosin; x400).

	Comment

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Millar in 1932 [2] and Fu in 1975 [3] described a rare form of a pigmented neural tumor arising from the sympathetic nervous system. Carney [1] named the tumor psammomatous melanotic schwannoma and described its association with a syndrome that bears his name. Carney’s syndrome, which is transmitted as a Mendelian autosomal dominant trait, is characterized by myxomas, spotty skin pigmentation, endocrine overactivity, and melanotic schwannomas. The myxomas affect the heart, skin, and breast and tend to be multiple in the involved organ. Nevi, which are also multiple, may occur on the extremities, trunk, and, less frequently, on the head and neck. The pituitary, adrenals, and thyroid may be hyperactive. More than half the patients with melanotic schwannoma have evidence of Carney’s syndrome. When the syndrome is present, the tumor tends to occur at an earlier age (average 22.5 years versus 33.2 years for persons without the syndrome).

Whereas the classic schwannoma is a benign tumor that never contains melanin or psammoma bodies, a melanotic schwannoma is a distinctive neoplasm that features both. Most commonly they are found in peripheral and posterior spine nerve roots near the midline. Unusual sites include the stomach, bones and soft tissues, heart, liver, and skin. Only 25 cases of a melanotic schwannoma originating in the respiratory tract have been reported (trachea, 1; bronchus, 7; and intrapulmonary, 17) [4–11].

Melanotic schwannomas are black, brown, or blue. Microscopically the tumor is incompletely encapsulated. Because the melanin pigment may be coarsely clumped or finely granular and varies from area to area, it is often difficult to make out cellular detail. Cell shapes vary from polygonal to spindle and blend from one to the other. This feature, along with the ill-defined borders of the cytoplasm that are ensheathed by layers of a continuous basal lamina, imparts a syncytial quality to the tumor. The nuclei may display intranuclear vacuoles typical of Schwann cells. Nuclear chromatism may be marked and the nucleoli may be quite prominent. Psammoma bodies are found in all cases. Electron microscopy demonstrates cells that resemble Schwann cells except for the presence of melanosomes, which exhibit a spectrum of maturation. Similar to dermal melanin, the pigment stains positive for Fontana’s stain and negative for iron and PAS. Immunostaining results are positive for S-100, vimentin, and a melanoma-associated antigen, HMB-45 antibody; and negative for chromogranin, synaptophysin, and keratin.

The biological behavior of these tumors is difficult to predict. Although most are characterized by slow growth, those with significant mitotic activity are considered malignant. Carney concluded that neither tumor size nor ploidy predicted metastatic potential and described four tumors that had metastasized.

In the case presented, no mitotic figures were seen, and the tumor appeared to be benign. Because of its location, a pneumonectomy could have been a reasonable option if the tumor had been a carcinoma. Performing a sleeve resection spared the lower lobe, and considering the benign nature of the tumor, the patient will continue to have essentially normal lung function.

	References

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1. Carney J.A. 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]
2. Millar W.G. A malignant melanotic tumor of ganglion cells arising from a thoracic sympathetic ganglion. J Pathol Bact 1932;35:351-357.
3. Fu Y.-S., Kaye G.I., Lattes R. Primary malignant melanocytic tumors of the sympathetic ganglia with an ultrastructural study of one. Cancer 1975;36:2029-2041.[Medline]
4. Gouin B., Holler A., Segal J., Lavasseur P. Schwannoma of the trachea. Poumon Coeur 1977;33:189-193.[Medline]
5. Rowlands D., Edwards C., Collins F. Malignant melanotic schwannoma of the bronchus. J Clin Pathol 1987;40:1449-1455.[Abstract/Free Full Text]
6. Uchiyama Y., Minami H., Yamashita M., et al. A case of intrapulmonary schwannoma and a review of the Japanese literature. Nippon Kyobu Shikkan Gakkai Zasshi 1989;37:1238-1241.
7. Umeki S., Kato H., Tsukiyama K., et al. A case of intrapulmonary schwannoma that should be disinguished from lung cancer. Nippon Kyobu Shikkan Gakkai Zasshi 1990;28:1635-1639.
8. Bosch X., Ramirez J., Font J., et al. Primary intrapulmonary benign schwannoma, a case with ultrastructural and immunohistochemical confirmation. Eur Respir J 1990;3:234-237.[Abstract]
9. Higashimoto Y., Ohata M., Kobayashi H., et al. A case of primary intrapulmonary benign schwannoma. Nippon Kyobu Shikkan Gakkai Zasshi 1991;29:360-364.
10. Michel J.L., de Montpreville V., Bobichon I., et al. Endo and exo-bronchial schwannoma treated by resection anastomosis of the left bronchial stump. Rev Mal Respir 1995;12:628-630.[Medline]
11. Nesbitt J.C., Vega D.M., Burke T., Mackay B. Cellular schwannoma of the bronchus. Ultrastruct Pathol 1996;20:349-354.[Medline]

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): David A. Simansky Alon Yellin Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Simansky, D. A. Articles by Yellin, A. Search for Related Content PubMed PubMed Citation Articles by Simansky, D. A. Articles by Yellin, A.