Dorsal dumb-bell melanotic schwannoma operated on by posterior and anterior approach: case report and a review of the literature.

The schwannomas are benign tumors originating from Schwann cells which constitute the nerve sheath. The dorsal pigmented type of schwannomas is relatively rare (Goldstein in Am J Med Genet 86:62-65, 2004; Kurtkaya-Yapicier in Histol Histopathol 18(3):925-934, 2003). There are two distinct types of melanotic schwannoma: the sporadic melanotic schwannomas and the psammomatous melanotic schwannomas of Carney complex. We report a case of a patient harboring a right dorsal dumb-bell melanotic schwannoma and left adrenal mass. The patient underwent a surgical procedure for en bloc total removal of the mass by a posterior and anterior approach. Histopathological examination revealed the diagnosis of melanotic schwannoma. At present, we have no reliable marker of histopathological malignancy of melanotic schwannoma so the follow-up period ought to continue for a period of more than 5 years. As the total removal of the melanotic neurinomas is mandatory to prevent possible malignant transformation of the tumor recurrence or regrowth, we believe that the posterior and trans-thoracic approach are the most suitable one for the dorsal dumb-bell schwannoma.

Introduction

Dorsal dumb-bell melanotic schwannomas are very rare [13]. They are rather frequently associated to Carney’s complex [8-10]. They present problems on different aspects, such as pre-operative diagnosis, surgical approach and post-operative course. We describe the case of a 53-year-old man who presented with left adrenal hyperplasia and right paravertebral mass suggesting a dumb-bell schwannoma.

Case report

Presentation and examination

In January 2003, a 53-year-old salesman, heavy smoker with an elevate level of arterial hypertension, began to complain about pain in his right chest and upper limb. Chest X-ray and thoracic CT scan in the following February revealed a D9–D10 dumb-bell mass extending into the intrathoracic right space for about 2.5 cm. The patient was admitted to our clinic. A spinal dorsal MRI confirmed the presence of the voluminous D9–D10 right paravertebral mass (Figs. 1, 2). Abdomen MRI showed an almost 4 cm swelling of the left suprarenal gland, suggesting a pheochromocytoma (Fig. 3). The neurologic examination and brain MRI were normal. The renal arterial echodoppler, the dosing of vanilmandelic acid, alpha-fetoprotein, carcinoembryonic antigen, urinary catecholamine and cortisol were normal. The renin activity and the plasmatic level of aldosteron resulted normal in orthostasis and increased in recumbency. The medullar adrenal gland scintigrams (123 IIs MIBG-148 MBqs e.v.) resulted negative for pheochromocytoma. Therefore, we excluded a pheochromocytoma and the patient underwent a surgical procedure for total removal of the dorsal mass by posterior and anterior approach in collaboration with the thoracic surgeons.

Fig. 1

MR images demonstrating a right dumb-bell intra-extradural mass at T9–T10 level extending into the intrathoracic right space for about 2.5 cm. Coronal and axial T1-weighted images with Gd-DTPA enhancement

Fig. 2

Sagittal T2-weighted MRI showing T9–T10 right intervertebral foramen occupied by the tumor

Fig. 3

Coronal abdominal spectral fat saturation inversion recovery (SPIR) MR images showing left suprarenal swelling

Operation

A D9–D10 laminectomy after radioscopic control was performed. A right dumb-bell intra-extradural mass of blackish aspect was seen. En bloc total removal of a markedly melanotic intradural lesion was achieved using operating microscope. Then the patient was placed in the left lateral decubitus and by trans-thoracic approach the paravertebral mass was radically removed en bloc, also freeing the right D9–D10 intervertebral foramen from the black and well-encapsulated neoformation. Accurate plastic of the paravertebral pleural wall was obtained. Histological examination revealed melanotic schwannoma with mitotic index not superior to one for ten fields on high magnification indicating low risk for malignancy.

Postoperative course

Post-operative course was uneventful, with marked improvement of the painful symptomatology and good healing of the surgical wounds. The patient was discharged from our ward after 10 days, with a recommendation for ichnographic controls of the left adrenal gland hyperplasia. During a 2-year follow-up period, no recurrence was evident on surveillance MRI.

Discussion

The schwannomas are benign tumors originating from Schwann cells which constitute the nerve sheath. The first case was described by Bjornboe [13, 15] in 1934 in a patient with neurofibromatosis type I. There are two distinct types of melanotic schwannoma: the sporadic and the psammomatous melanotic schwannomas of Carney complex [8, 14, 24, 27, 29, 36]. In 1985, Carney described a syndrome characterized by mixomas (heart, skin and breast), mucus-cutaneous spotty pigmentations and endocrine overactivity (due to thyroid dysfunction or hypophysial adenoma or Cushing syndrome secondary to adrenocortical pigmented primary nodular hyperplasia) [8, 9].

A year later, a Mendelian dominant heredity was defined responsible for the symptomatologic complex [43]. About 50% of patients with melanotic psammomatous schwannomas are affected by the syndrome of Carney and one-fifth of them are carriers of multiple lesions [21, 42]. Generally, melanotic schwannoma affects the spinal nerves, the central nervous system and the autonomous nerve system, but extra-nervous locations can also exist. The dorsal location represents 30.5% of the spinal melanotic schwannoma [41]. Until today we were able to find 47 spinal cases of extramedullary melanotic neurinoma in literature (Table 1) [1, 2, 3, 5, 6, 7, 11, 12, 13, 16, 18, 20, 21, 26, 28, 30, 31, 33, 34, 35, 38, 39, 44, 45]. The clinical presentation is not specific but similar to that of other extramedullary spinal tumors (radicular pain, dysesthesias, progressive sensorial-motor deficits). Preoperative diagnosis is based on magnetic resonance imaging (MRI): melanotic schwannomas appear hyperintense on T1-weighted sequences and hypointense on T2-weighted sequences compared to the nonmelanotic type of schwannomas that are hypo-isointense on T1 and hyperintense on T2 [1, 13, 17, 25, 37].

Table 1

Review of 47 cases of spinal extramedullary melanotic schwannoma reported in literature

References	Age	Gender	Level
Aprile et al. [1]	70	F	L3
Bagchi et al. [2]	40	M	T6–T7
Belak et al. [3]	44	–	Dorsal
Bosman et al. [4]	43	M	L4–L5
Bouziani et al. [5]	46	M	Lumbar
Buhl et al. [6]	28	M	L5–S1
Bunc et al. [7]	–	–	T12–L2
Cornejo et al. [10]	36	M	L3–L4
Di Gregorio et al. [11]	–	–	Sacral
Erlandson et al. [12]	36	M	L5–S1
Goasguen et al. [13]	66	F	C2–C3
Graziani et al. [15]	40	F	T3
Gregorios et al. [16]	45	F	T2
Iizuka et al. [18]	58	F	T10
Killeen et al. [19]	26	F	S1
Krichen et al. [20]	27	M	C6–C7
Kuchelmeister et al. [21]	53	F	C5–C6
Le Cam et al. [23]	35	F	L4
Leger et al. [24]	36	M	C4
Lowman et al. [26]	17	F	T12–L1
Lowman et al. [26]	26	F	C6
Ludvikova et al. [27]	56	F	Spine
Ludvikova et al. [27]	58	M	Spine
Mandybur et al. [28]	59	M	T7
Martin-Reay et al. [29]	32	M	Sacrum
McGavran et al. [30]	12	F	T2
McGavran et al. [30]	49	F	C8
Mennemeyer et al. [31]	23	F	L1
Mennemeyer et al. [31]	25	M	T7
Mennemeyer et al. [31]	36	M	S1
Parent et al. [33]	63	F	S1
Paris et al. [34]	49	F	C8
Parker et al. [35]	18	F	Dorsal
Prieto-Rodriguez et al. [36]	38	M	T5
Schmitz et al. [38]	42	F	Cervical
Tawk et al. [39]	61	M	T7
Vallat-Decouvelaere et al. [41]	5 cases	F and M	C–T–L–S
Zhang et al. [44]	5 cases	F and M	Spinal nerve root
Zonenshayn et al. [45]	27	F	L2 and L4–L5

The histological differential diagnosis with the other spinal pigmented tumors is with the meningeal melanocitoma, the pigmented neurofibroma, the paraganglioma, the ganglioneuroma, the fibrous form of meningioma and above all with the primitive melanoma or relative metastasis [13, 15]. Even if the association of the left adrenal swelling and arterial hypertension with the dumb-bell thoracic melanotic schwannoma can be correlated to the Carney complex, in our opinion our patient did not harbor such a syndrome. In fact only the adrenocortical pigmented primary nodular hyperplasia is a characteristic stigmata of Carney complex. Moreover, our patient did not show cutaneous signs of neurofibromatosis and his family history was negative for Carney complex stigmata. The total body CT scan showed the left adrenal mass and excluded any other typical lesion of the syndrome. The increased plasmatic level of renin and aldosteron in recumbency in our patient, that was on heavy medical therapy for high level of arterial blood pressure, may be correlated to left adrenal hyperplasia or solitary adrenal adenoma [40] and not to adrenocortical pigmented nodular hyperplasia, which is the cause of ACTH-independent adrenal Cushing’s syndrome [8] and normally do not trigger elevation of plasmatic aldosteron. Moreover, in our case the histological examination of the neurinoma did not show the most common, psammomatous aspect of Carney complex [8, 13]. In summary, we did not perform a left adrenal biopsy as we ruled out the Carney syndrome and malignancy of the adrenal mass by clinic and radiological investigations. Hypertension, adrenal mass and dumb-bell melanotic schwannoma do not imply Carney complex.

In our patient the hypertension was not correlated to the Carney complex, but to the hyperaldosteronism caused by left adrenal hyperplasia or solitary adrenal adenoma. Nevertheless, neurosurgeons ought to keep in mind the connection between the melanotic schwannoma and the Carney complex, since more than 50% of the cases described in literature have been related to such syndrome. A complete endocrinological evaluation and a total body CT should always be performed together with a genetic study in the suspicion of Carney complex. The risk of possible malignant transformation of the neurinoma should also be taken into consideration as cases of recurrences or metastases have been described even 13 years after surgery [4, 6, 19, 21, 23, 32, 41]. It is not possible to have any reliable histopathological indication of possible malignant transformation after the first surgical operation [42]. The follow-up ought to continue for a period of more than 5 years. We have both to check the primitive tumor regrowth or recurrence and the possible remote locations, particularly in the lungs.

From the surgical point of view the total removal of the melanotic neurinomas is mandatory to prevent possible malignant transformation of the tumor remnants. The therapeutic potential of radiotherapy is not proven [42]. The prognosis depends, therefore, almost entirely on the extent of surgical removal of the tumor [3, 44]. So we believe that the posterior and anterior approach is the most suitable one to remove the dorsal dumb-bell schwannoma completely, both in the thoracic cavity and in the intervertebral foramen, and to avoid possible liquoral leakage.