Primary Psammomatous Melanotic Schwannoma of the Spine Selim Bakan, MD, Yasemin Kayadibi, MD, Ezel Ersen, MD, Betul Vatankulu, MD, Nil Ustundag, MD, and Zehra Isık Hasıloglu, MD Departments of Radiology, Division of Neuroradiology, Thoracic Surgery, Nuclear Medicine, and Pathology, Cerrahpasa Medical Faculty, Istanbul University Kocamustafapasa, Istanbul, Turkey
Schwannoma is an easily identifiable and frequently diagnosed lesion of the spinal column. However, if the schwannoma contains a melanin component, the diagnosis is challenging. Our purpose in this case report is to discuss the imaging and histopathologic findings of a rarely seen psammomatous type of melanotic schwannoma diagnosed in a 31-year-old woman. (Ann Thorac Surg 2015;99:e141–3) Ó 2015 by The Society of Thoracic Surgeons
M
elanotic schwannomas are melanin-containing nerve sheath tumors that are very rare neoplasms and constitute only 1% of peripheral nerve sheath tumors. Accepted for publication Feb 12, 2015. Address correspondence to Dr Hasiloglu, Department of Radiology, Cerrahpasa Medical Faculty, Istanbul University, Kocamustafapasa, Istanbul, Turkey, 34098; e-mail: [email protected].
There are a few theories about the etiopathogenesis of these tumors, including melanomatous transformation of Schwann neoplastic cells and phagocytosis of melanin by Schwann cells. The 2 types of melanotic schwannomas have been described as psammomatous and sporadic. Psammomatous types usually present as a component of Carney complex [1–3]. In this case report, we describe a very rarely seen primary spinodorsal psammomatous type of melanotic schwannoma in a 31-year-old woman who had none of the features of Carney complex. A 31-year-old woman presented to our radiology department with back pain. She had no abnormalities in her neurologic examination. There was no history of significant trauma or primary malignancy. Spinal magnetic resonance imaging (MRI) and computed tomography (CT) were performed. MRI revealed a paravertebral extrapleural soft tissue mass measuring about 2.5 cm that originated from the spinal canal and extended into the neural foramen at the level of T4-5. The mass had focal hyperintensity on T1-weighted (T1W) imaging, and there was a cystic component that appeared as hypointense on T1W images and hyperintense on T2-weighted (T2W) images (Fig 1). After contrast administration, the lesion showed enhancement. CT showed punctate calcifications inside this soft tissue lesion. Positron emission tomography (PET)/CT was also performed so as not to miss a possible metastasis or primary malignancy.
Fig 1. (A) Axial and (E) sagittal T1-weighted (T1W) images showing paravertebral, extrapleural, dumbbell-shaped soft tissue mass with focal hyperintensity that is significant for melanin component. Lesion originated from spinal canal and extended into neural foramen at the level of T4-5. Arrow indicating the cystic component of the lesion on (B) axial and (D) sagittal T2-weighted (T2W) images. (C) Axial and (F) sagittal T1W images after intravenous contrast administration showing enhanced lesion. Ó 2015 by The Society of Thoracic Surgeons Published by Elsevier
0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2015.02.060
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CASE REPORT BAKAN ET AL PSAMMOMATOUS MELANOTIC SCHWANNOMA
Ann Thorac Surg 2015;99:e141–3
Fig 2. (A) Axial computed tomography (CT), (B) positron emission tomography/CT (PET/CT) fusion, and (C) 18F-fluorodeoxyglucose (FDG) PET images showing punctuate calcifications inside soft tissue lesion and increased FDG uptake.
18F-fluorodeoxyglucose (FDG)-PET/CT was performed 105 minutes after intravenous injection of FDG. Scanning revealed an increased FDG uptake (standard uptake value (SUV)max ¼ 6.6) in the lesion, but no other significant uptake that could be considered pathologic was detected in any part of the skeletal system (Fig 2). The lesion was considered a benign tumoral mass, but the possibility of malignancy could not be excluded. The patient underwent operation. After a posterolateral thoracotomy, the lesion was excised with the thoracic nerve, which was surrounded by the mass (Fig 3). The postoperative period was uneventful. Pathologic examination revealed spindle-shaped Schwann cells and melaninpigmented cells that showed positive staining for S-100 protein (biochemical marker of melanotic and neuroepithelial differentiation) and HMB-45 (biochemical marker of melanotic differentiation). The immunohistochemical and histologic analyses were diagnostic for a psammomatous type of melanotic schwannoma (Fig 4). At 6-month follow-up, spinal MRI revealed no recurrence.
Comment Melanotic schwannoma is an intermediate tumor between schwannoma and malignant melanoma, both of them originate from neuroectodermal tissues. These lesions are very rarely seen and are usually located intracranially, but intraspinal and extraaxial types have also been reported [1, 4]. Patients usually present in the fourth decade of life with symptoms resulting from compression of adjacent structures. These tumors are usually benign, but malignant degeneration, recurrence, and metastasis have been reported in 26% to 38.9% of the cases in the literature [1, 4]. There are 2 subtypes of melanotic schwannoma—the psammomatous type and the sporadic type. The psammomatous type coexists with Carney complex in 50% of cases and is characterized by myxoma (cardiac, cutaneous, mammary), pigmentation, and endocrinopathy with autosomal dominant inheritance [1–5]. Our patient had no clinical or physical findings and no family history that supported Carney complex. There are no characteristic diagnostic radiologic features for melanotic schwannomas, so it is sometimes challenging to distinguish them from other melanin-containing
tumors. On computed tomographic images, these lesions are seen as hyperdense masses with calcifications. On MRI, the melanotic component causes T1 and T2 shortening because of the paramagnetic effect of the melanin, but on both T1W and T2W images, the signal intensity of the lesion could be variable because of the concentration of the melanin component. They typically show enhancement after contrast administration. Melanin-containing lesions, which include malignant melanoma, melanocytoma, pigmented neurofibroma, paraganglioma, leptomeningeal melanosis, hemorrhagic metastatic lesions in breast cancer, thyroid cancer, choriocarcinoma, and lung cancer must be considered in the differential diagnosis because these are other reasons for T1 shortening [5]. FDG PET could be used for differentiating benign peripheral nerve sheath tumors from malignant ones. However, on PET, high uptake of FDG with a wide range of SUVs, from 0.33 to 12, has been reported previously in schwannomas. The exact cause is not known, but variable cellularity of the schwannomas could be suggested for this variable SUV; for this reason, the value of PET/CT is limited in distinguishing schwannomas from malignant lesions [2, 6]. Spindle-shaped Schwann cells with melanosomes, psammoma bodies, and positive immunoactivity for melanotic markers such as S-100 protein, vimentin, and HMB-45 are characteristic features of melanotic
Fig 3. Specimen showing peripherally pigmented lesion involving thoracic nerve.
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Fig 4. (A) Common nuclear and cytoplasmic positivity for S-100 (magnification, 100). (B) Moderate positivity for HMB-45 (magnification, 200).
schwannomas seen on immunohistopathologic examination. Positivity for S-100 protein and HMB-45 could also be positive in malignant melanoma, but the absence of psammoma bodies, infiltrative patency, increased mitotic activity, necrosis, and nuclear pleomorphisms are suggested differential entities for malignant melanoma [3, 5, 7]. Although complete resection is sufficient for the treatment of both sporadic and psammomatous types of melanotic schwannoma, malignant transformation and recurrence of the tumor must always be kept in mind, and follow-up imaging of the patient should continue for at least 5 years. Postsurgical radiation therapy or immunotherapy could be added to therapy for melanotic schwannomas, but the clinical value of these additional treatment modalities has not been demonstrated [1, 3, 4]. In summary, schwannoma should be always be kept in mind when a neural foraminal mass is detected in the spinal column. If the lesion shows hyperintensity on T1W images, this appearance should be suggestive of melanincontaining or hemorrhagic pathologic conditions. The psammomatous type of schwannoma exists with the Carney complex in 50% of cases, so a patient should be investigated further if Carney complex is present. There is no characteristic clinical or imaging finding. The exact
diagnosis is confirmed only with surgical intervention and immunohistopathologic examination.
References 1. De Cerchio L, Contratti F, Fraioli MF. Dorsal dumb-bell melanotic schwannoma operated by posterior and anterior approach: case report and a review of the literature. Eur Spine J 2006;5:664–9. 2. De Waele M, Carp L, Lauwers P, et al. Paravertebral schwannoma with high uptake of fluorodeoxyglucose on positron emission tomography. Acta Chir Belg 2005;105:537–8. 3. Smith AB, Rushing EJ, Smirniotopoulos JG. Pigmented lesions of the central nervous system: radiologic-pathologic correlation. Radiographics 2009;5:1503–24. 4. Marton E, Feletti A, Orvieto E, Longatti P. Dumbbell-shaped C-2 psammomatous melanotic malignant schwannoma: case report and review of the literature. J Neurosurg Spine 2007;6: 591–9. 5. Stratakis CA, Kirschner LS, Carney JA. Clinical and molecular features of the Carney complex: diagnostic criteria and recommendations for patient evaluation. J Clin Endocrinol Metab 2001;86:4041–6. 6. Moon H, Park SJ, Kim SR, Park HS, Lee YC. Benign intercostal schwannoma mimicking a solitary metastasis from lung cancer. Thorax 2009;65:753–4. 7. Martinez Izquerdo MA, Lopez-Soto V, Saenz-Santamaria J, Larcruz- Palea C. Intraoperative cytological findings in two cases of psammomatous melanotic schwannoma. Cytopathology 2011;22:60–2.
Schwannoma is an easily identifiable and frequently diagnosed lesion of the spinal column. However, if the schwannoma contains a melanin component, the diagnosis is challenging. Our purpose in this case report is to discuss the imaging and histopathologic findings of a rarely seen psammomatous type of melanotic schwannoma diagnosed in a 31-year-old woman. (Ann Thorac Surg 2015;99:e141–3) Ó 2015 by The Society of Thoracic Surgeons
M
elanotic schwannomas are melanin-containing nerve sheath tumors that are very rare neoplasms and constitute only 1% of peripheral nerve sheath tumors. Accepted for publication Feb 12, 2015. Address correspondence to Dr Hasiloglu, Department of Radiology, Cerrahpasa Medical Faculty, Istanbul University, Kocamustafapasa, Istanbul, Turkey, 34098; e-mail: [email protected].
There are a few theories about the etiopathogenesis of these tumors, including melanomatous transformation of Schwann neoplastic cells and phagocytosis of melanin by Schwann cells. The 2 types of melanotic schwannomas have been described as psammomatous and sporadic. Psammomatous types usually present as a component of Carney complex [1–3]. In this case report, we describe a very rarely seen primary spinodorsal psammomatous type of melanotic schwannoma in a 31-year-old woman who had none of the features of Carney complex. A 31-year-old woman presented to our radiology department with back pain. She had no abnormalities in her neurologic examination. There was no history of significant trauma or primary malignancy. Spinal magnetic resonance imaging (MRI) and computed tomography (CT) were performed. MRI revealed a paravertebral extrapleural soft tissue mass measuring about 2.5 cm that originated from the spinal canal and extended into the neural foramen at the level of T4-5. The mass had focal hyperintensity on T1-weighted (T1W) imaging, and there was a cystic component that appeared as hypointense on T1W images and hyperintense on T2-weighted (T2W) images (Fig 1). After contrast administration, the lesion showed enhancement. CT showed punctate calcifications inside this soft tissue lesion. Positron emission tomography (PET)/CT was also performed so as not to miss a possible metastasis or primary malignancy.
Fig 1. (A) Axial and (E) sagittal T1-weighted (T1W) images showing paravertebral, extrapleural, dumbbell-shaped soft tissue mass with focal hyperintensity that is significant for melanin component. Lesion originated from spinal canal and extended into neural foramen at the level of T4-5. Arrow indicating the cystic component of the lesion on (B) axial and (D) sagittal T2-weighted (T2W) images. (C) Axial and (F) sagittal T1W images after intravenous contrast administration showing enhanced lesion. Ó 2015 by The Society of Thoracic Surgeons Published by Elsevier
0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2015.02.060
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CASE REPORT BAKAN ET AL PSAMMOMATOUS MELANOTIC SCHWANNOMA
Ann Thorac Surg 2015;99:e141–3
Fig 2. (A) Axial computed tomography (CT), (B) positron emission tomography/CT (PET/CT) fusion, and (C) 18F-fluorodeoxyglucose (FDG) PET images showing punctuate calcifications inside soft tissue lesion and increased FDG uptake.
18F-fluorodeoxyglucose (FDG)-PET/CT was performed 105 minutes after intravenous injection of FDG. Scanning revealed an increased FDG uptake (standard uptake value (SUV)max ¼ 6.6) in the lesion, but no other significant uptake that could be considered pathologic was detected in any part of the skeletal system (Fig 2). The lesion was considered a benign tumoral mass, but the possibility of malignancy could not be excluded. The patient underwent operation. After a posterolateral thoracotomy, the lesion was excised with the thoracic nerve, which was surrounded by the mass (Fig 3). The postoperative period was uneventful. Pathologic examination revealed spindle-shaped Schwann cells and melaninpigmented cells that showed positive staining for S-100 protein (biochemical marker of melanotic and neuroepithelial differentiation) and HMB-45 (biochemical marker of melanotic differentiation). The immunohistochemical and histologic analyses were diagnostic for a psammomatous type of melanotic schwannoma (Fig 4). At 6-month follow-up, spinal MRI revealed no recurrence.
Comment Melanotic schwannoma is an intermediate tumor between schwannoma and malignant melanoma, both of them originate from neuroectodermal tissues. These lesions are very rarely seen and are usually located intracranially, but intraspinal and extraaxial types have also been reported [1, 4]. Patients usually present in the fourth decade of life with symptoms resulting from compression of adjacent structures. These tumors are usually benign, but malignant degeneration, recurrence, and metastasis have been reported in 26% to 38.9% of the cases in the literature [1, 4]. There are 2 subtypes of melanotic schwannoma—the psammomatous type and the sporadic type. The psammomatous type coexists with Carney complex in 50% of cases and is characterized by myxoma (cardiac, cutaneous, mammary), pigmentation, and endocrinopathy with autosomal dominant inheritance [1–5]. Our patient had no clinical or physical findings and no family history that supported Carney complex. There are no characteristic diagnostic radiologic features for melanotic schwannomas, so it is sometimes challenging to distinguish them from other melanin-containing
tumors. On computed tomographic images, these lesions are seen as hyperdense masses with calcifications. On MRI, the melanotic component causes T1 and T2 shortening because of the paramagnetic effect of the melanin, but on both T1W and T2W images, the signal intensity of the lesion could be variable because of the concentration of the melanin component. They typically show enhancement after contrast administration. Melanin-containing lesions, which include malignant melanoma, melanocytoma, pigmented neurofibroma, paraganglioma, leptomeningeal melanosis, hemorrhagic metastatic lesions in breast cancer, thyroid cancer, choriocarcinoma, and lung cancer must be considered in the differential diagnosis because these are other reasons for T1 shortening [5]. FDG PET could be used for differentiating benign peripheral nerve sheath tumors from malignant ones. However, on PET, high uptake of FDG with a wide range of SUVs, from 0.33 to 12, has been reported previously in schwannomas. The exact cause is not known, but variable cellularity of the schwannomas could be suggested for this variable SUV; for this reason, the value of PET/CT is limited in distinguishing schwannomas from malignant lesions [2, 6]. Spindle-shaped Schwann cells with melanosomes, psammoma bodies, and positive immunoactivity for melanotic markers such as S-100 protein, vimentin, and HMB-45 are characteristic features of melanotic
Fig 3. Specimen showing peripherally pigmented lesion involving thoracic nerve.
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Fig 4. (A) Common nuclear and cytoplasmic positivity for S-100 (magnification, 100). (B) Moderate positivity for HMB-45 (magnification, 200).
schwannomas seen on immunohistopathologic examination. Positivity for S-100 protein and HMB-45 could also be positive in malignant melanoma, but the absence of psammoma bodies, infiltrative patency, increased mitotic activity, necrosis, and nuclear pleomorphisms are suggested differential entities for malignant melanoma [3, 5, 7]. Although complete resection is sufficient for the treatment of both sporadic and psammomatous types of melanotic schwannoma, malignant transformation and recurrence of the tumor must always be kept in mind, and follow-up imaging of the patient should continue for at least 5 years. Postsurgical radiation therapy or immunotherapy could be added to therapy for melanotic schwannomas, but the clinical value of these additional treatment modalities has not been demonstrated [1, 3, 4]. In summary, schwannoma should be always be kept in mind when a neural foraminal mass is detected in the spinal column. If the lesion shows hyperintensity on T1W images, this appearance should be suggestive of melanincontaining or hemorrhagic pathologic conditions. The psammomatous type of schwannoma exists with the Carney complex in 50% of cases, so a patient should be investigated further if Carney complex is present. There is no characteristic clinical or imaging finding. The exact
diagnosis is confirmed only with surgical intervention and immunohistopathologic examination.
References 1. De Cerchio L, Contratti F, Fraioli MF. Dorsal dumb-bell melanotic schwannoma operated by posterior and anterior approach: case report and a review of the literature. Eur Spine J 2006;5:664–9. 2. De Waele M, Carp L, Lauwers P, et al. Paravertebral schwannoma with high uptake of fluorodeoxyglucose on positron emission tomography. Acta Chir Belg 2005;105:537–8. 3. Smith AB, Rushing EJ, Smirniotopoulos JG. Pigmented lesions of the central nervous system: radiologic-pathologic correlation. Radiographics 2009;5:1503–24. 4. Marton E, Feletti A, Orvieto E, Longatti P. Dumbbell-shaped C-2 psammomatous melanotic malignant schwannoma: case report and review of the literature. J Neurosurg Spine 2007;6: 591–9. 5. Stratakis CA, Kirschner LS, Carney JA. Clinical and molecular features of the Carney complex: diagnostic criteria and recommendations for patient evaluation. J Clin Endocrinol Metab 2001;86:4041–6. 6. Moon H, Park SJ, Kim SR, Park HS, Lee YC. Benign intercostal schwannoma mimicking a solitary metastasis from lung cancer. Thorax 2009;65:753–4. 7. Martinez Izquerdo MA, Lopez-Soto V, Saenz-Santamaria J, Larcruz- Palea C. Intraoperative cytological findings in two cases of psammomatous melanotic schwannoma. Cytopathology 2011;22:60–2.
