MALIGNANT
SCHWANNOMA
OF THE INFERIOR DENTAL
NERVE
By D. J. DAVID’,B. SPECULAND,’ B. VERNON-ROBERTS,:’ and R. P. SACH’ ‘Plastic Surgery Unit, Royal Adelaide Hospital, 2 Department of Oral Pathology and Oral Surgeq-, The University of Adelaide and 3 Professor of Pathology, The University of Adelaide, and Head (lf Division of Tissue Pathology, The Institute of Medical and Veterinarv Science, Adelaid,?
MALIGNANT schwannomas arise Je nom or in patients with von Recklinghausen’s neurofibromatosis, of which IO to I 5 per cent experience malignant change (De Vore and Waldron, 1961). The benign neurilemoma is believed not to undergo malignant change (D’Agostino et al., 1963; Harkin and Reed, 1969). In a series of 155 cases of malignant schwannoma, 30 cases (26 per cent) were associated with von Recklinghausen’s disease. This association is thought to carry a poorer prognosis since only 30 per cent of those cases associated with von Recklinghausen’s disease survived 5 years in contrast to 66 per cent for the whole group (Ghosh ef al., 1973). Economou et al. (1958) have commented on the risk of venous spread of malignant schwannoma and also suggested that the ability to travel along a nerve may be due to multicentric origin simulating metastasis. We found II previously reported cases of malignant schwannoma of the inferior dental nerve (Table I). Four began with a lip ulcer or tumour which was excised. In I instance the initial histopathology report indicated squamous cell carcinoma and this was not queried until 3 years later when the true nature of the lesion was revealed (De Vore and Waldron, 1961). The delay between initial excision of lower lip lesions and more obvious development of malignant schwannoma of the inferior dental nerve ranged from 6 months to 5 years. Seven cases were not preceded by an initial lip lesion. The radiological findings also present 2 varieties; there may be either a cystic lesion of the mandible or a more obvious cylindrical enlargement of the inferior dental canal. Nine other oral cases of malignant schwannoma have been reported and are listed in Table 2. We present here 2 new cases of malignant schwannoma of the inferior dental nerve which illustrate the 2 varieties of clinical presentation and radiological findings. Case I. A 55-year-old man had a left mental nerve anaesthesia and a non-ulcerated swelling of his left mandible involving the buccal sulcus of the premolar area. Some 5 years previously he had received irradiation to his lower lip for a lesion diagnosed elsewhere as a squamous cell carcinoma, and on recurrence of the tumour I year later, had a wedge excision of his lip. No neck nodes were palpable, but X-ray of his mandible showed a marked cylindrical enlargement of the left inferior dental canal from foramen to mandibular foramen (Fig. I). A biopsy revealed the presence of a malignant tumour with extensive growth along a nerve Address for reprints: B. Speculand, Department of Adelaide 5000, South Australia.
of Oral Pathology and Oral Surgery, The University
323
BRITISH
324
JOURNAL
OF PLASTIC
TABLE
SURGERY
I
Malignant schwannoma of the inferior dental nerve A:
INITIAL LOWER LIP LESION (4) Age Sex VRD
De Vore and Waldron
Economou
Lewis
et al.
and Hart
Wise and Asbury
M
No
56
M
No
41
M
No
31
M
No
INITIAL LIP LESION (7) 65 F
B: No Bell Cuneo
65
No
and Rand
37
M
No
et al.
30
M
No
14
F
No
F
No
;
No No
De Larue Haywood
Ingram Villa and Bunag Wilson and Walsh
4$ 23 2
AW AR D VRD
trunk.
Premolar region mandible Burning numbness lip and chin. Mental foramen ID canal to Gasserian ganglion Premolar region mandible and ID canal Mental foramen and ID canal to Gasserian ganglion Decidous molar region and lingual penetration Mass Mandible = = = =
alive and well alive . . and recurrence died von Recklinghausen’s
Outcome
Treatment
History I. “V” excision for lip ulcer -“SCC” 3 years previously - _ _ 2. numbness and shooting pains mental foramen and ID canal (Diabetic) I. excision lump lip 2 yrs previously 2. mental foramen and ID canal I. multiple enucleations of lip tumour 5 yrs previously 2. mental foramen and ID canal intracranial spread I. “V” excision lip sarcoma 6 months previously 2. mental foramen and ID canal to Gasserian ganglion
Irradiation
AR 20 mo
Hemimandibulectomy
AW9yr
Hemimandibulectomy
D 5 yr
Lip excision Hemimandibulectomy Craniotomy
AW6mo
Surgical removal and cautery Excision Cautery Craniotomy
-
Excision
AR6mo
Hemimandibulectomy
D I yr
Resection
AR Io mo
Surgical -
removal
AR3mo
-
disease
The tumour was made up of spindle cells with scanty cytoplasm, arranged in intercells were lacing fascicles and exhibiting numerous mitotic figures. Occasional multinucleate also present. The appearances were those of a malignant schwannoma (Fig. 2). The whole of the left half of his mandible from midline to temporomandibular joint was excised and the inferior dental nerve was sectioned as high as possible. A simultaneous block dissection of the left side of the neck was also performed. The excised mandible was decalcified and opened along the inferior dental canal. The inferior dental nerve was markedly thickened by a homogeneous grey-white tumour (Fig. 3). The tumour cells were arranged in interlacing coarse bundles, whorls and occasional herring-bone patterns (Fig. 4a). The plump spindle cells had moderate nuclear pleomorphism (Fig. 4b) and there were occasional bizarre giant multinucleate cells; mitoses were frequent in many areas. There was also a polyhedral epithelioid component with the cells arranged in solid rounded nests (Fig. 4~).
MALIGNANT
SCHWANNOMA
OF THE
TABLE
INFERIOR
D”NTAL
NERVE
325
II
Other oral cases of malignant schwannoma Age Sex VRD Blankenship (:utler
et al.
and Gross
Economou
ct ul.
Millard
Frc.
I.
et d. and Busser
Treatment
52
F
Yes
32
F
No
50
M
No
59
M
No
Maxilla-metastasis to lungs Cystic maxillary and palatal lesion Nodule right commissure mouth Tumour upper lip
I4
!z
No No
Left buccal mucosa Left upper lip
6
F
No
Submandibular
47
M
No
Periostcum
42
F
No
Maxilla
20
Eversolc
History
Orthopantomogram
showing
mass
of mandible
cylindrical enlargement mental foramen.
Outcome
Irradiation
AR 6 wk
Irradiation
AR 6 mu
Excision
AW2yr
Excision
D s yr (other causes AW3yr D 5 yr intra-
Excision Excision (recurred with cranial spread) Hemimandibulectomy and submandibular dissection Excision and hemimandibulectomy Irradiation
of inferior
dental
canal
and
AW 4 yr
AWr5mo D4mo
enlarged
left
BRITISH
326
FIG.~.
Case
1 0
I.
JOURNAL
OF PLASTIC
SURGERY
Medium power view of tumour removed at initial biopsy, Tumour composed of spindle cells arranged in interlacing fascicles. H & E. x 200.
I
1
/
2
3
4
5
6
1 7
ems FIG. 3. Case
I.
Bisected mandible showing generalised enlargement of the inferior dental nerve with a marked nodular expansion in one area.
MALIGNANT
SCHWANNOMA
OF THE
INFERIOR
DENTAL
NERVE
3’7
Fro. 4. Case I. a. Low power view of tumour within inferior dental nerve. Tumour composed of interlacing bundles of spindle cells and cells arranged in rounded nests. H & E. y too. h. High power view of spindle cell portion of Fig. 4a. Shows spindle cells exhibiting a moderate degree of nuclear pleomorphism. H &E. T 400. c. High power view of cell nest shown in Fig. _+a. Shows epithelioid differentiation within the tumour. H&E. x400.
These microscopic appearances were considered to be those of a malignant schwannoma On electron microscopy of formalin fixed paraffin with areas of epithelioid differentiation. embedded material we found the frequent presence of extracellular basement membrane type material with varying amounts of collagen between the tumour cells (Fig. 5). This was considered to support the view that the tumour was of Schwann cell origin. Tumour was present in the proximal end of the inferior dental nerve at the line of surgical resection and also at the anterior line of surgical resection of the mandible at the midline where the tumour was infiltrating cancellous bone via the medial neural elements. There was no tumour present in lymph nodes or any other part of the specimen. During convalescence he had a grand-ma1 fit. Although no radiological or brain-scan evidence of intracranial tumour was detected, tumour was found in the trigeminal ganglion after a transcranial approach. Further surgery was futile. His cerebral function slowly but progressively deteriorated in association with intracranial tumour spread and he died 18 months after his mandibulectomy. of the lip were reviewed; the appearances Slides of the previously excised “carcinoma” were very similar to those of the alveolar tumour and were consistent with a diagnosis of malignant schwannoma (Fig. 6). Case 2. A 59-year-old obese alcoholic diabetic presented to his general dental practitioner with loose mandibular teeth associated with a cyst-like lesion of the anterior mandible (Fig 7aj. He returned 4 weeks later with right mental nerve The loose anterior teeth were removed.
328
BRITISH
JOURNAL
OF
PLASTIC
SURGERY
anaesthesia and a swelling involving the healing sockets. A biopsy confirmed malignant schwannoma. Radiology now showed an irregular expansion of the mandible from the left central incisor to the right canine. The margins were less well defined with superior and anterior cortical expansion. The anterior margin clearly showed irregularity due to new bone spicules (Fig. 7b). At operation, a frozen section of the right inferior dental nerve at the lingula was obtained via an Obwegeser sagittal split approach. This was free of tumour, as was a frozen section of the mental nerve. The mandible, from right angle to left canine, was resected by a combined intra- and extra-oral approach. Immediate frozen section and subsequent paraffin section established complete excision and the patient is free of disease some 3 months postoperatively. When the excised mandible was bisected the right inferior dental nerve was found in continuity with tumour tissue (Fig. S), which histologically had a spindle cell growth pattern, the cells arranged in whorls and interlacing fascicles and with frequent mitotic figures (Fig. 9) consistent with a diagnosis of malignant schwannoma. The presence of extracellular basement membrane material on electron microscopy supported the view that the tumour was of Schwann cell origin. Tumour cells were found along the incisive branch of the inferior dental nerve 5 mm from the main tumour (Fig. IO).
Fig. 5. Case I. a. Electron micrograph of formalin-fixed paraffin embedded material. Shows extracellular basement membrane type material (BM) with varying amounts of collagen between the tumour cells. x 12,000. b. Electron micrograph showing relationship between thick layer of extracellular filamentous basement membrane type material (BM), collagen fibres (C) and tumour cell nucleus (N). x 39,000
MALIGNANT
SCHWANNOMA
OF
THE
INFERIOR
DENTAL
NERVE
329
DISCUSSION
The rarity of malignant schwannoma of the inferior dental nerve is supported by the absence of other recorded cases in South Australia and the total of only 13 cases now reported in the literature. Ghosh et al. found I 15 cases of malignant schwannoma form the records of the Memorial Sloan-Kettering Cancer Center between 1920 and 1970; 16 (14 per cent) involved the head and neck. Economou et al. reported 14 cases of malignant schwannoma of cranial nerve origin, of which I affected the inferior dental nerve. Thus approximately I per cent of all malignant schwannomas may affect the inferior dental nerve. The wide age distribution of those with inferior dental nerve lesions accords with the findings of Ghosh et al. for malignant schwannoma in general. However, the :r3 inferior dental nerve cases and the g other oral cases show a sex distribution of 2M : I F in contrast to that of IM : 1e4F recorded by Ghosh et al. In each of the cases described here, the tumour fulfilled the following criteria for the histopathological diagnosis of malignant schwannoma: The tumour was situated within a nerve trunk and extending along it; There was unequivocal evidence of malignancy within the tumour with invasion of the epineurium; There was electron microscopic evidence for the origin of the tumour from Schwann cells, i.e. extracellular basement membrane material and intercellular collagen.
Fig. 6.
Case I.
power view of tumour removed from left lower lip 5 years previously. H & E. ,’ 100. spindle cell tumour extending along a nerve trunk.
Low
Shov,,s
2
BRITISH
330
FIG. 7.
Case 2.
JOURNAL
OF PLASTIC
SURGERY
a. Periapical radiographs of loose anterior teeth at presentation to general dental practitioner. b. 4 weeks after removal of loose anterior teeth.
MALIGNANT
FIG. X. Case 2.
SCHWANNOMA
OF
THE
INFERIOR
DENTAL
NERVE
331
Bisected mandible showing inferior dental nerve (elevated by white marker) in continuity with tumour contained in the biopsy cavity in the mandible.
There were some epithelioid features in Case I but in neither case was there any evidence of pre-existing plexiform neurofibroma, rhadbomyosarcomatous differentiation, cartilaginous metaplasia or necrosis as has been described in malignant schwannoma in other sites (Harkin and Reed; Ghosh et al.). Malignant schwannoma of the inferior dental nerve may extend as far proximally as the trigeminal ganglion and distally across the midline of the mandible via &-a-osseous nerve fibres supplying the mandibular incisors. Distant metastasis is by venous spread, particularly to the lungs (Economou et al.). Therefore an initial chest radiograph. is mandatory. Since the tumour does not metastasise via lymphatics, a prophylactic block dissection of the neck probably has little place in surgical management. The 2 cases reported and the review of the literature suggest a specific surgical approach. Frozen sections of biopsies from the mental nerve and the proximal inferior dental nerve at the lingula should first be studied. The excision can be extended anteriorly until tumour free tissue is found. If the biopsy at the lingula is positive, it is necessary to biopsy the trigeminal ganglion by craniotomy. If the ganglion is tumour free, it is possible to resect a core of tissue containing the involved nerve up to the ganglion, by a combined intracranial and extracranial approach. The prognosis of malignant schwannoma of the inferior dental nerve is poor. Only I case was alive and well beyond 5 years (Table I). In contrast, Ghosh et al. report 66 per cent j-year survival for malignant schwannoma in general. Nineteen of their 103 cases available for follow-up study subsequently developed recurrence such that the IO-year survival rate dropped to 58 per cent. Clearly when dealing with the mandibular nerve, excision is wasted if the route to the brain is not inspected at the beginning.
332
BRITISH
JOURNAL
OF
PLASTIC
SURGERY
FIG. 9. Case 2. a. Low power view of section through turnour removed from right mandible. Shows tumour composed of spindle cells arranged in whorls and interlacing fascicles with some degree of palisading. H & E. x IOO. b. High power view of portion of Fig. ga. Tumour composed of slender and plump spindle cells with moderate nuclear pleomorphism and scattered mitotic figures. H & E. x 400.
MALIGNANT
Fro. to
Case 2.
SCHWANNOMA
OF
THE
INFERIOR
DENTAL
NERVE
333
High power view of section through inferior dental nerve showing tumour cells extending along a nerve 0.5 cm distal to the main tumour mass. H & E. * 300.
We wish to thank Mr D. N. Robinson, Director, Plastic Surgery Unit, Royal Adelaide Hospital, for his helpful crticism of the manuscript; Dr N. D. M. Harvey, Director, Radiotherapv Unit, Royal Adelaide Hospital, for referring Case I; Dr B. N. Fitzpatrick, 79 Penniqton TerracL,, North Adelaide, for referring Case 2; aud Miss S. Williamson for the typing. REFERENCES
D’AGOSTINO,A. N., SOULE, E. H. and MILLER, R. H. (1963). Primary malignant neoplasm> of nerves (malignant neurilemomas) in patients without manifestations of multiple neurofibromatosis (von Recklinghausen’s disease). Cancer, 16, 1003. DE VORE, D. T. and WALDRON, C. A. (1969). Malignant peripheral nerve tumours of the oral cavity : Review of the literature and report of a case. Oral Stqt’ry, Oral Medicine.. and Oral Pathology, 14, 56. ECONOMOU, S. G., SOUTHWICK, H. W. and SLAUGHTER, D. P. (1958) Neurofibrosarcomas of cranial nerve origin. Archmt5 of Surgery, 77, 271. GHOSH, R. L., GHOSH, L., Huvos, A. G. and FORTNER, J. G. (1973). Malignant schwannoma: A clinicopathologic study. Cmcer, 31, 184. HARKIN, J. L. and REED, R. J. (1969). Malignant primary nerve sheath tumours. In “Turnours of the peripheral nervous system”, p. 107. Atlas of Tumor Pathology, Second Series. Washington, D.C. : Armed Forces Institute of Pathology.
31
4-F
SCHWANNOMA
OF THE INFERIOR DENTAL
NERVE
By D. J. DAVID’,B. SPECULAND,’ B. VERNON-ROBERTS,:’ and R. P. SACH’ ‘Plastic Surgery Unit, Royal Adelaide Hospital, 2 Department of Oral Pathology and Oral Surgeq-, The University of Adelaide and 3 Professor of Pathology, The University of Adelaide, and Head (lf Division of Tissue Pathology, The Institute of Medical and Veterinarv Science, Adelaid,?
MALIGNANT schwannomas arise Je nom or in patients with von Recklinghausen’s neurofibromatosis, of which IO to I 5 per cent experience malignant change (De Vore and Waldron, 1961). The benign neurilemoma is believed not to undergo malignant change (D’Agostino et al., 1963; Harkin and Reed, 1969). In a series of 155 cases of malignant schwannoma, 30 cases (26 per cent) were associated with von Recklinghausen’s disease. This association is thought to carry a poorer prognosis since only 30 per cent of those cases associated with von Recklinghausen’s disease survived 5 years in contrast to 66 per cent for the whole group (Ghosh ef al., 1973). Economou et al. (1958) have commented on the risk of venous spread of malignant schwannoma and also suggested that the ability to travel along a nerve may be due to multicentric origin simulating metastasis. We found II previously reported cases of malignant schwannoma of the inferior dental nerve (Table I). Four began with a lip ulcer or tumour which was excised. In I instance the initial histopathology report indicated squamous cell carcinoma and this was not queried until 3 years later when the true nature of the lesion was revealed (De Vore and Waldron, 1961). The delay between initial excision of lower lip lesions and more obvious development of malignant schwannoma of the inferior dental nerve ranged from 6 months to 5 years. Seven cases were not preceded by an initial lip lesion. The radiological findings also present 2 varieties; there may be either a cystic lesion of the mandible or a more obvious cylindrical enlargement of the inferior dental canal. Nine other oral cases of malignant schwannoma have been reported and are listed in Table 2. We present here 2 new cases of malignant schwannoma of the inferior dental nerve which illustrate the 2 varieties of clinical presentation and radiological findings. Case I. A 55-year-old man had a left mental nerve anaesthesia and a non-ulcerated swelling of his left mandible involving the buccal sulcus of the premolar area. Some 5 years previously he had received irradiation to his lower lip for a lesion diagnosed elsewhere as a squamous cell carcinoma, and on recurrence of the tumour I year later, had a wedge excision of his lip. No neck nodes were palpable, but X-ray of his mandible showed a marked cylindrical enlargement of the left inferior dental canal from foramen to mandibular foramen (Fig. I). A biopsy revealed the presence of a malignant tumour with extensive growth along a nerve Address for reprints: B. Speculand, Department of Adelaide 5000, South Australia.
of Oral Pathology and Oral Surgery, The University
323
BRITISH
324
JOURNAL
OF PLASTIC
TABLE
SURGERY
I
Malignant schwannoma of the inferior dental nerve A:
INITIAL LOWER LIP LESION (4) Age Sex VRD
De Vore and Waldron
Economou
Lewis
et al.
and Hart
Wise and Asbury
M
No
56
M
No
41
M
No
31
M
No
INITIAL LIP LESION (7) 65 F
B: No Bell Cuneo
65
No
and Rand
37
M
No
et al.
30
M
No
14
F
No
F
No
;
No No
De Larue Haywood
Ingram Villa and Bunag Wilson and Walsh
4$ 23 2
AW AR D VRD
trunk.
Premolar region mandible Burning numbness lip and chin. Mental foramen ID canal to Gasserian ganglion Premolar region mandible and ID canal Mental foramen and ID canal to Gasserian ganglion Decidous molar region and lingual penetration Mass Mandible = = = =
alive and well alive . . and recurrence died von Recklinghausen’s
Outcome
Treatment
History I. “V” excision for lip ulcer -“SCC” 3 years previously - _ _ 2. numbness and shooting pains mental foramen and ID canal (Diabetic) I. excision lump lip 2 yrs previously 2. mental foramen and ID canal I. multiple enucleations of lip tumour 5 yrs previously 2. mental foramen and ID canal intracranial spread I. “V” excision lip sarcoma 6 months previously 2. mental foramen and ID canal to Gasserian ganglion
Irradiation
AR 20 mo
Hemimandibulectomy
AW9yr
Hemimandibulectomy
D 5 yr
Lip excision Hemimandibulectomy Craniotomy
AW6mo
Surgical removal and cautery Excision Cautery Craniotomy
-
Excision
AR6mo
Hemimandibulectomy
D I yr
Resection
AR Io mo
Surgical -
removal
AR3mo
-
disease
The tumour was made up of spindle cells with scanty cytoplasm, arranged in intercells were lacing fascicles and exhibiting numerous mitotic figures. Occasional multinucleate also present. The appearances were those of a malignant schwannoma (Fig. 2). The whole of the left half of his mandible from midline to temporomandibular joint was excised and the inferior dental nerve was sectioned as high as possible. A simultaneous block dissection of the left side of the neck was also performed. The excised mandible was decalcified and opened along the inferior dental canal. The inferior dental nerve was markedly thickened by a homogeneous grey-white tumour (Fig. 3). The tumour cells were arranged in interlacing coarse bundles, whorls and occasional herring-bone patterns (Fig. 4a). The plump spindle cells had moderate nuclear pleomorphism (Fig. 4b) and there were occasional bizarre giant multinucleate cells; mitoses were frequent in many areas. There was also a polyhedral epithelioid component with the cells arranged in solid rounded nests (Fig. 4~).
MALIGNANT
SCHWANNOMA
OF THE
TABLE
INFERIOR
D”NTAL
NERVE
325
II
Other oral cases of malignant schwannoma Age Sex VRD Blankenship (:utler
et al.
and Gross
Economou
ct ul.
Millard
Frc.
I.
et d. and Busser
Treatment
52
F
Yes
32
F
No
50
M
No
59
M
No
Maxilla-metastasis to lungs Cystic maxillary and palatal lesion Nodule right commissure mouth Tumour upper lip
I4
!z
No No
Left buccal mucosa Left upper lip
6
F
No
Submandibular
47
M
No
Periostcum
42
F
No
Maxilla
20
Eversolc
History
Orthopantomogram
showing
mass
of mandible
cylindrical enlargement mental foramen.
Outcome
Irradiation
AR 6 wk
Irradiation
AR 6 mu
Excision
AW2yr
Excision
D s yr (other causes AW3yr D 5 yr intra-
Excision Excision (recurred with cranial spread) Hemimandibulectomy and submandibular dissection Excision and hemimandibulectomy Irradiation
of inferior
dental
canal
and
AW 4 yr
AWr5mo D4mo
enlarged
left
BRITISH
326
FIG.~.
Case
1 0
I.
JOURNAL
OF PLASTIC
SURGERY
Medium power view of tumour removed at initial biopsy, Tumour composed of spindle cells arranged in interlacing fascicles. H & E. x 200.
I
1
/
2
3
4
5
6
1 7
ems FIG. 3. Case
I.
Bisected mandible showing generalised enlargement of the inferior dental nerve with a marked nodular expansion in one area.
MALIGNANT
SCHWANNOMA
OF THE
INFERIOR
DENTAL
NERVE
3’7
Fro. 4. Case I. a. Low power view of tumour within inferior dental nerve. Tumour composed of interlacing bundles of spindle cells and cells arranged in rounded nests. H & E. y too. h. High power view of spindle cell portion of Fig. 4a. Shows spindle cells exhibiting a moderate degree of nuclear pleomorphism. H &E. T 400. c. High power view of cell nest shown in Fig. _+a. Shows epithelioid differentiation within the tumour. H&E. x400.
These microscopic appearances were considered to be those of a malignant schwannoma On electron microscopy of formalin fixed paraffin with areas of epithelioid differentiation. embedded material we found the frequent presence of extracellular basement membrane type material with varying amounts of collagen between the tumour cells (Fig. 5). This was considered to support the view that the tumour was of Schwann cell origin. Tumour was present in the proximal end of the inferior dental nerve at the line of surgical resection and also at the anterior line of surgical resection of the mandible at the midline where the tumour was infiltrating cancellous bone via the medial neural elements. There was no tumour present in lymph nodes or any other part of the specimen. During convalescence he had a grand-ma1 fit. Although no radiological or brain-scan evidence of intracranial tumour was detected, tumour was found in the trigeminal ganglion after a transcranial approach. Further surgery was futile. His cerebral function slowly but progressively deteriorated in association with intracranial tumour spread and he died 18 months after his mandibulectomy. of the lip were reviewed; the appearances Slides of the previously excised “carcinoma” were very similar to those of the alveolar tumour and were consistent with a diagnosis of malignant schwannoma (Fig. 6). Case 2. A 59-year-old obese alcoholic diabetic presented to his general dental practitioner with loose mandibular teeth associated with a cyst-like lesion of the anterior mandible (Fig 7aj. He returned 4 weeks later with right mental nerve The loose anterior teeth were removed.
328
BRITISH
JOURNAL
OF
PLASTIC
SURGERY
anaesthesia and a swelling involving the healing sockets. A biopsy confirmed malignant schwannoma. Radiology now showed an irregular expansion of the mandible from the left central incisor to the right canine. The margins were less well defined with superior and anterior cortical expansion. The anterior margin clearly showed irregularity due to new bone spicules (Fig. 7b). At operation, a frozen section of the right inferior dental nerve at the lingula was obtained via an Obwegeser sagittal split approach. This was free of tumour, as was a frozen section of the mental nerve. The mandible, from right angle to left canine, was resected by a combined intra- and extra-oral approach. Immediate frozen section and subsequent paraffin section established complete excision and the patient is free of disease some 3 months postoperatively. When the excised mandible was bisected the right inferior dental nerve was found in continuity with tumour tissue (Fig. S), which histologically had a spindle cell growth pattern, the cells arranged in whorls and interlacing fascicles and with frequent mitotic figures (Fig. 9) consistent with a diagnosis of malignant schwannoma. The presence of extracellular basement membrane material on electron microscopy supported the view that the tumour was of Schwann cell origin. Tumour cells were found along the incisive branch of the inferior dental nerve 5 mm from the main tumour (Fig. IO).
Fig. 5. Case I. a. Electron micrograph of formalin-fixed paraffin embedded material. Shows extracellular basement membrane type material (BM) with varying amounts of collagen between the tumour cells. x 12,000. b. Electron micrograph showing relationship between thick layer of extracellular filamentous basement membrane type material (BM), collagen fibres (C) and tumour cell nucleus (N). x 39,000
MALIGNANT
SCHWANNOMA
OF
THE
INFERIOR
DENTAL
NERVE
329
DISCUSSION
The rarity of malignant schwannoma of the inferior dental nerve is supported by the absence of other recorded cases in South Australia and the total of only 13 cases now reported in the literature. Ghosh et al. found I 15 cases of malignant schwannoma form the records of the Memorial Sloan-Kettering Cancer Center between 1920 and 1970; 16 (14 per cent) involved the head and neck. Economou et al. reported 14 cases of malignant schwannoma of cranial nerve origin, of which I affected the inferior dental nerve. Thus approximately I per cent of all malignant schwannomas may affect the inferior dental nerve. The wide age distribution of those with inferior dental nerve lesions accords with the findings of Ghosh et al. for malignant schwannoma in general. However, the :r3 inferior dental nerve cases and the g other oral cases show a sex distribution of 2M : I F in contrast to that of IM : 1e4F recorded by Ghosh et al. In each of the cases described here, the tumour fulfilled the following criteria for the histopathological diagnosis of malignant schwannoma: The tumour was situated within a nerve trunk and extending along it; There was unequivocal evidence of malignancy within the tumour with invasion of the epineurium; There was electron microscopic evidence for the origin of the tumour from Schwann cells, i.e. extracellular basement membrane material and intercellular collagen.
Fig. 6.
Case I.
power view of tumour removed from left lower lip 5 years previously. H & E. ,’ 100. spindle cell tumour extending along a nerve trunk.
Low
Shov,,s
2
BRITISH
330
FIG. 7.
Case 2.
JOURNAL
OF PLASTIC
SURGERY
a. Periapical radiographs of loose anterior teeth at presentation to general dental practitioner. b. 4 weeks after removal of loose anterior teeth.
MALIGNANT
FIG. X. Case 2.
SCHWANNOMA
OF
THE
INFERIOR
DENTAL
NERVE
331
Bisected mandible showing inferior dental nerve (elevated by white marker) in continuity with tumour contained in the biopsy cavity in the mandible.
There were some epithelioid features in Case I but in neither case was there any evidence of pre-existing plexiform neurofibroma, rhadbomyosarcomatous differentiation, cartilaginous metaplasia or necrosis as has been described in malignant schwannoma in other sites (Harkin and Reed; Ghosh et al.). Malignant schwannoma of the inferior dental nerve may extend as far proximally as the trigeminal ganglion and distally across the midline of the mandible via &-a-osseous nerve fibres supplying the mandibular incisors. Distant metastasis is by venous spread, particularly to the lungs (Economou et al.). Therefore an initial chest radiograph. is mandatory. Since the tumour does not metastasise via lymphatics, a prophylactic block dissection of the neck probably has little place in surgical management. The 2 cases reported and the review of the literature suggest a specific surgical approach. Frozen sections of biopsies from the mental nerve and the proximal inferior dental nerve at the lingula should first be studied. The excision can be extended anteriorly until tumour free tissue is found. If the biopsy at the lingula is positive, it is necessary to biopsy the trigeminal ganglion by craniotomy. If the ganglion is tumour free, it is possible to resect a core of tissue containing the involved nerve up to the ganglion, by a combined intracranial and extracranial approach. The prognosis of malignant schwannoma of the inferior dental nerve is poor. Only I case was alive and well beyond 5 years (Table I). In contrast, Ghosh et al. report 66 per cent j-year survival for malignant schwannoma in general. Nineteen of their 103 cases available for follow-up study subsequently developed recurrence such that the IO-year survival rate dropped to 58 per cent. Clearly when dealing with the mandibular nerve, excision is wasted if the route to the brain is not inspected at the beginning.
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FIG. 9. Case 2. a. Low power view of section through turnour removed from right mandible. Shows tumour composed of spindle cells arranged in whorls and interlacing fascicles with some degree of palisading. H & E. x IOO. b. High power view of portion of Fig. ga. Tumour composed of slender and plump spindle cells with moderate nuclear pleomorphism and scattered mitotic figures. H & E. x 400.
MALIGNANT
Fro. to
Case 2.
SCHWANNOMA
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High power view of section through inferior dental nerve showing tumour cells extending along a nerve 0.5 cm distal to the main tumour mass. H & E. * 300.
We wish to thank Mr D. N. Robinson, Director, Plastic Surgery Unit, Royal Adelaide Hospital, for his helpful crticism of the manuscript; Dr N. D. M. Harvey, Director, Radiotherapv Unit, Royal Adelaide Hospital, for referring Case I; Dr B. N. Fitzpatrick, 79 Penniqton TerracL,, North Adelaide, for referring Case 2; aud Miss S. Williamson for the typing. REFERENCES
D’AGOSTINO,A. N., SOULE, E. H. and MILLER, R. H. (1963). Primary malignant neoplasm> of nerves (malignant neurilemomas) in patients without manifestations of multiple neurofibromatosis (von Recklinghausen’s disease). Cancer, 16, 1003. DE VORE, D. T. and WALDRON, C. A. (1969). Malignant peripheral nerve tumours of the oral cavity : Review of the literature and report of a case. Oral Stqt’ry, Oral Medicine.. and Oral Pathology, 14, 56. ECONOMOU, S. G., SOUTHWICK, H. W. and SLAUGHTER, D. P. (1958) Neurofibrosarcomas of cranial nerve origin. Archmt5 of Surgery, 77, 271. GHOSH, R. L., GHOSH, L., Huvos, A. G. and FORTNER, J. G. (1973). Malignant schwannoma: A clinicopathologic study. Cmcer, 31, 184. HARKIN, J. L. and REED, R. J. (1969). Malignant primary nerve sheath tumours. In “Turnours of the peripheral nervous system”, p. 107. Atlas of Tumor Pathology, Second Series. Washington, D.C. : Armed Forces Institute of Pathology.
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