J Neurosurg 75:795-797, 1991
Neuromuscular hamartoma (benign "triton" tumor) of the brachial plexus Case report DEEPAK AWASTHI, M.D., DAVID G. KLINE, M.D., AND EDWIN N. BECKMAN~ M.D. Department of Neurosurgery, Louisiana State University Medical Center, and Ochsner Foundation Hospital, and Department of Pathology, Ochsner Clinic and Alton Ochsner Medical Foundation, New Orleans, Louisiana t~ Neuromuscular hamartoma (choristoma) or benign "triton" tumor is a very rare peripheral-nerve tumor composed of mature nerve fibers and well-differentiated striated muscle fibers. Only seven cases have been reported in the literature. A new case of this rare entity is described in a 36-year-old white woman with a recurrent left supraclavicular mass in the brachial plexus area. Unlike the previous cases, this patient had continued to have proliferation of her tumor since childhood, requiring total resection in adulthood. It is concluded that total resection of these tumors should be attempted at initial diagnosis. The histogenesis of these tumors remains unclear. They may represent proliferation of neuroectodermal-derived or limb mesodermal tissue in the elements of a peripheral nerve. KEY WORDS brachial plexus peripheral-nerve tumor 9
9
histogenesis
9
choristoma
9
hamartoma
9
C a s e Report
It was considered that the tumor could not be completely removed without causing paralysis of the left arm, and a partial resection was performed. The resected tumor consisted microscopically of dense fibrous tissue interdigitating into skeletal muscle. Immediately after the resection, the patient had shown some paresis of the left arm and hand which eventually improved. The surgeons decided to follow this tumor without any additional surgical intervention. The patient had continued to do well until she developed the symptoms described above.
This 36-year-old white woman presented with a tender supraclavicular mass. Her main symptoms included numbness of the left hand and forearm as well as shortness of breath during exercise. These symptoms persisted for the 3 months prior to admission. She denied any noticeable weakness in her left upper extremity. The patient was referred to our clinic after magnetic resonance imaging had revealed a large mass in the left brachial plexus area. In 1954, the patient had undergone a partial resection of a left supraclavicular mass at the age of 7 months. During the initial surgery the mass was noted to involve intimately the brachial plexus and the subclavian artery.
Examination. On physical examination at the Ochsner Foundation Hospital, the patient had a firm, tender 5 • 3-cm left supraclavicular mass. The left arm was considerably smaller and shorter than the right arm. Motor examination revealed mild weakness (4/5) of the following muscles: the left brachioradialis, triceps, flexor and extensor digitorum profundi, supinator, abductor pollicis longus, and hand intrinsics. Sensory examination revealed decreased sensation to pin prick and light touch in the left hand and forearm (at the C6-7 nerve root distribution). The biceps and triceps reflexes were decreased on the left compared to the right.
A
NEUROMUSCULARhamartoma (choristoma) or benign "triton" tumor is a very rare peripheralnerve tumor composed of mature nerve fibers a n d well-differentiated striated muscle fibers/ Only seven cases have been reported in the literature. L2'4'5 We report a new case of this rare entity. The findings are compared with those of the other cases, followed by a brief discussion of the histogenesis of this tumor.
J. Neurosurg. / Volume 75 /November, 1991
795
D. Awasthi, D. G. Kline, and E. N. Beckman
FIG. 1. Photomicrograph of the resected lesion showing nerve (thin arrows) erratically admixed with skeletal muscle (thick arrows9 and fibrous tissue fcurved arrow~J. H & E, x 50.
Operation. The left brachial plexus was explored through a standard anterior approach. A large (8 x 6 • 4-cm) firm, poorly defined mass, grayish-tan in color, was seen in the supraclavicular area. It extended under a thinned clavicle into the infraclavicular area. Elements of the brachial plexus entered the mass and appeared to be exiting from the center of the lesion in the inffaclavicular region. This large fibrous mass also engulfed the subclavian artery. The elements of the brachial plexus were painstakingly dissected from the mass using sharp techniques under loupe magnification. The C-7 nerve root and the middle trunk were the most intimately involved of the brachial plexus elements. Intraoperative recordings, after gross total resection of the mass, revealed small nerve action potentials from the C-5 and C-6 nerve roots to the upper trunk and the lateral cord as well as from the C-8 nerve root to the lower trunk. No nerve action potentials were elicited from the C-7 nerve root to the middle trunk or from the T-1 nerve root to the lower trunk. Thus, there was some sparing of the brachial plexus elements (especially the upper trunk) after tumor resection. Frozen biopsy specimens obtained during the operation revealed only fibrous tissue with no neoplasm; therefore, we decided to repair the damaged elements of the brachial plexus with sural nerve grafts. A total of four 3.5- to 4-in. grafts were placed from the resected fascicular bundles of the C-6, C-7, and C-8 nerve roots to the fascicular bundles of the posterior and medial cords. Pathological Examination. The gross appearance of the mass was that of a solid, firm, poorly defined fibrous tissue grayish-tan in color. Histologically, the mass was composed of mature nerve fibers (almost entirely myelinated) admixed with benign-appearing skeletal muscle fibers (Fig. 1). Often the muscle fibers had a modest increase in diameter. There were areas with nerve and striated muscle fibers incorporated 796
FI(;. 2. Photomicrograph of the resected lesion showing skeletal muscle fibers (arrom9 within the nerve fascicle. H & E.x 125.
within the same fascicle (Fig. 2). Nerve and muscle fibers were also varyingly admixed with dense fibrous tissue. No area had the appearance of rhabdomyoma or the suggestion of malignancy. Postoperative Course, As expected, the patient had paralysis of her left arm. There was trace function in the left deltoid and biceps muscles. The left serratus anterior muscle was intact. A cerebrospinal fluid leak developed from the incision site, which was drained. Otherwise, the postoperative course was uneventful. The follow-up period is too short for adequate assessment of the left upper-extremity motor function. Discussion
Terminology Malignant neural tumors have been known to contain mesenchymal components histologically indistinguishable from osteosarcoma, chondrosarcoma, leiomyosarcoma, liposarcoma, angiosareoma, and rhabdomyosarcoma. 5 A malignant schwannoma with rhabdomyoblasts is called a "triton" tumor.3 "Triton" tumor refers to the experiments by Locatelli in 1925 who implanted cut ends of the sciatic nerve subcutaneously in the back of tritons (salamanders of the genus Triturus), thus inducing the formation of supernumerary limbs containing bone and muscle tissue. 3 Masson 6 in 1932 was the first to consider the "triton" tumor as a separate entity. Since this first report, 27 more cases have been published in the literature. 2 Patients with the malignant form of "triton" tumor have a very poor prognosis with a rapid fatal course] These neoplasms are usually associated with von Recklinghausen's disease. On the other hand, a benign form of the "triton" tumor composed of mature nerve fibers and well-differentiated skeletal muscle fibers rarely occurs in peripheral nerves. This neoplasm is even rarer than the malignant variety. J. Neurosurg. / Volume 75 / November, 1991
Neuromuscular hamartoma of brachial plexus Clinical Aspects of Benign "Triton'" Tumors Only seven cases of neuromuscular benign "triton" tumors have been reported in the literature, z'2'4'5 The patients were four boys and three girls; all were diagnosed within the first 5 years of life, and three tumors were present at birth. All seven patients presented with a mass, but only one had any neurological deficit at presentation? None of the patients had any evidence of von Recklinghausen's disease. The tumors were located in the brachial plexus in four cases, sciatic nerve in two cases, and the median nerve in one case. Microscopically, the tumors were composed of nerve fibers and mature striated muscle. Two patients had resection of the tumor with subsequent recurrent masses in the same area, which on reexploration consisted only of dense fibrous tissue. Postoperatively, one of these patients developed paresis of the involved nerves that gradually improved over 4 years. One patient had three recurrences of the mass; the diagnosis of neuromuscular choristoma (hamartoma) was made after resection of the third recurrence. This patient presented at the age of 14 years with marked atrophy of the fight arm and absence of movement about the shoulder. A right forequarter amputation with resection of the first rib and exploration of the thoracic inlet were performed in this patient at the third recurrence? Another patient with a left brachial plexus tumor had a 90% resection. Postoperatively, this patient developed a nearly complete and permanent paralysis of the left arm with sparing of flexor muscles of the hand.t The only patient who presented with a neurological deficit had a partial tumor resection and was lost to follow-up reviewJ Of the remaining two patients, one underwent a biopsy and one a partial resection. The biopsy resulted in nerve paresis, which gradually improved. Tumors in these two cases regressed in 1 and 3 years, respectively. 4 Our patient is similar to the above cases in that there was presentation at birth with a palpable mass and no neurological deficits. A review of the slides from the original biopsy in 1954 revealed a mixture of fibrous tissue and skeletal muscle without any evidence of nerve fibers. It is our presumption, however, that the original mass had areas with the morphological appearance of a neuromuscular hamartoma. The tumor in our patient did not regress spontaneously after partial resection; instead it proliferated to a large size over a period of 35 years. This fact could argue against conservative surgical management (biopsy or partial resection) of these nerve tumors as suggested by Chen. 2 Complete resection of this neoplasm might be at-
J. Neurosurg. / Volume 75 /November, 1991
tempted at the initial presentation to prevent future neurological deficits and related deformities.
Histogenesis. The histogenesis of benign "triton" tumors remains unclear. Louhimo and Rapola 4 suggested that these tumors could arise in a peripheral nerve as a result of incorporation of the limb mesenchymal tissue within the nerve sheaths as the embryonic nerves extended peripherally and became ensheathed by neurilemma. On the other hand, mesodermal-like tissue can derive directly from neuroectodermal cells. 5 Masson 6 used this hypothesis to explain the histogenesis of malignant "triton" tumors; he believed that the neoplastic Schwann cells could transform into striated muscles. This concept is in accord with the theory of ectodermal origin of meningeal mesenchyme, embryogenesis of iris muscles from the eye cup, occurrence of primary rhabdomyosarcomas in the iris and cerebellum, and rhabdomyosarcomatous elements in medulloblastomas and medulloepitheliomas. 5 Conclusions
Neuromuscular hamartomas (choristomas) or benign "triton" tumors represent a distinct group of slowgrowing peripheral-nerve tumors with a good long-term prognosis and unclear histogenesis, These tumors may continue to proliferate over many years if left untreated. References
1. Bonneau R, Brochu P: Neuromuscular choristoma. A clinicopathologic study of two cases, Am J Surg Pathol 7:521-528, 1983 2. Chen KTK: Neuromuscular hamartoma. J Surg Oncol 26:158-160, 1984 3. Dewit L, Albus-Lntter CE, de Jong ASH, et al: Malignant schwannoma with a rhabdomyoblasfic component, a socalled triton tumor. A clinicopathologic study. Cancer 58: 1350-1356, 1986 4. Louhimo I, Rapola J: lntraneural muscular hamartoma: rel~ort of two cases in small children. J Pediatr Surg 7: 696-699, 1972 5. Markel SF, Enzinger FM: Neuromuscular hamartomaa benign "triton tumor" composed of mature neural and striated muscle elements. Cancer 49:140-144, 1982 6. Masson P: Recklinghausen's neurofibromatosis, sensory neuromas and motor neuromas, in: Contributions to the Medical Sciences in Honor of Dr. Emannel Libman. New York: International Press, 1932, Vol 2, pp 793-802 Manuscript received January 2, 1991. Accepted in final form April 30, 1991. Address reprint requests to: Deepak Awasthi, M.D., Department of Neurosurgery, Louisiana State University Medical Center, 1542 Tulane Avenue, New Orleans, Louisiana 70112.
797
Neuromuscular hamartoma (benign "triton" tumor) of the brachial plexus Case report DEEPAK AWASTHI, M.D., DAVID G. KLINE, M.D., AND EDWIN N. BECKMAN~ M.D. Department of Neurosurgery, Louisiana State University Medical Center, and Ochsner Foundation Hospital, and Department of Pathology, Ochsner Clinic and Alton Ochsner Medical Foundation, New Orleans, Louisiana t~ Neuromuscular hamartoma (choristoma) or benign "triton" tumor is a very rare peripheral-nerve tumor composed of mature nerve fibers and well-differentiated striated muscle fibers. Only seven cases have been reported in the literature. A new case of this rare entity is described in a 36-year-old white woman with a recurrent left supraclavicular mass in the brachial plexus area. Unlike the previous cases, this patient had continued to have proliferation of her tumor since childhood, requiring total resection in adulthood. It is concluded that total resection of these tumors should be attempted at initial diagnosis. The histogenesis of these tumors remains unclear. They may represent proliferation of neuroectodermal-derived or limb mesodermal tissue in the elements of a peripheral nerve. KEY WORDS brachial plexus peripheral-nerve tumor 9
9
histogenesis
9
choristoma
9
hamartoma
9
C a s e Report
It was considered that the tumor could not be completely removed without causing paralysis of the left arm, and a partial resection was performed. The resected tumor consisted microscopically of dense fibrous tissue interdigitating into skeletal muscle. Immediately after the resection, the patient had shown some paresis of the left arm and hand which eventually improved. The surgeons decided to follow this tumor without any additional surgical intervention. The patient had continued to do well until she developed the symptoms described above.
This 36-year-old white woman presented with a tender supraclavicular mass. Her main symptoms included numbness of the left hand and forearm as well as shortness of breath during exercise. These symptoms persisted for the 3 months prior to admission. She denied any noticeable weakness in her left upper extremity. The patient was referred to our clinic after magnetic resonance imaging had revealed a large mass in the left brachial plexus area. In 1954, the patient had undergone a partial resection of a left supraclavicular mass at the age of 7 months. During the initial surgery the mass was noted to involve intimately the brachial plexus and the subclavian artery.
Examination. On physical examination at the Ochsner Foundation Hospital, the patient had a firm, tender 5 • 3-cm left supraclavicular mass. The left arm was considerably smaller and shorter than the right arm. Motor examination revealed mild weakness (4/5) of the following muscles: the left brachioradialis, triceps, flexor and extensor digitorum profundi, supinator, abductor pollicis longus, and hand intrinsics. Sensory examination revealed decreased sensation to pin prick and light touch in the left hand and forearm (at the C6-7 nerve root distribution). The biceps and triceps reflexes were decreased on the left compared to the right.
A
NEUROMUSCULARhamartoma (choristoma) or benign "triton" tumor is a very rare peripheralnerve tumor composed of mature nerve fibers a n d well-differentiated striated muscle fibers/ Only seven cases have been reported in the literature. L2'4'5 We report a new case of this rare entity. The findings are compared with those of the other cases, followed by a brief discussion of the histogenesis of this tumor.
J. Neurosurg. / Volume 75 /November, 1991
795
D. Awasthi, D. G. Kline, and E. N. Beckman
FIG. 1. Photomicrograph of the resected lesion showing nerve (thin arrows) erratically admixed with skeletal muscle (thick arrows9 and fibrous tissue fcurved arrow~J. H & E, x 50.
Operation. The left brachial plexus was explored through a standard anterior approach. A large (8 x 6 • 4-cm) firm, poorly defined mass, grayish-tan in color, was seen in the supraclavicular area. It extended under a thinned clavicle into the infraclavicular area. Elements of the brachial plexus entered the mass and appeared to be exiting from the center of the lesion in the inffaclavicular region. This large fibrous mass also engulfed the subclavian artery. The elements of the brachial plexus were painstakingly dissected from the mass using sharp techniques under loupe magnification. The C-7 nerve root and the middle trunk were the most intimately involved of the brachial plexus elements. Intraoperative recordings, after gross total resection of the mass, revealed small nerve action potentials from the C-5 and C-6 nerve roots to the upper trunk and the lateral cord as well as from the C-8 nerve root to the lower trunk. No nerve action potentials were elicited from the C-7 nerve root to the middle trunk or from the T-1 nerve root to the lower trunk. Thus, there was some sparing of the brachial plexus elements (especially the upper trunk) after tumor resection. Frozen biopsy specimens obtained during the operation revealed only fibrous tissue with no neoplasm; therefore, we decided to repair the damaged elements of the brachial plexus with sural nerve grafts. A total of four 3.5- to 4-in. grafts were placed from the resected fascicular bundles of the C-6, C-7, and C-8 nerve roots to the fascicular bundles of the posterior and medial cords. Pathological Examination. The gross appearance of the mass was that of a solid, firm, poorly defined fibrous tissue grayish-tan in color. Histologically, the mass was composed of mature nerve fibers (almost entirely myelinated) admixed with benign-appearing skeletal muscle fibers (Fig. 1). Often the muscle fibers had a modest increase in diameter. There were areas with nerve and striated muscle fibers incorporated 796
FI(;. 2. Photomicrograph of the resected lesion showing skeletal muscle fibers (arrom9 within the nerve fascicle. H & E.x 125.
within the same fascicle (Fig. 2). Nerve and muscle fibers were also varyingly admixed with dense fibrous tissue. No area had the appearance of rhabdomyoma or the suggestion of malignancy. Postoperative Course, As expected, the patient had paralysis of her left arm. There was trace function in the left deltoid and biceps muscles. The left serratus anterior muscle was intact. A cerebrospinal fluid leak developed from the incision site, which was drained. Otherwise, the postoperative course was uneventful. The follow-up period is too short for adequate assessment of the left upper-extremity motor function. Discussion
Terminology Malignant neural tumors have been known to contain mesenchymal components histologically indistinguishable from osteosarcoma, chondrosarcoma, leiomyosarcoma, liposarcoma, angiosareoma, and rhabdomyosarcoma. 5 A malignant schwannoma with rhabdomyoblasts is called a "triton" tumor.3 "Triton" tumor refers to the experiments by Locatelli in 1925 who implanted cut ends of the sciatic nerve subcutaneously in the back of tritons (salamanders of the genus Triturus), thus inducing the formation of supernumerary limbs containing bone and muscle tissue. 3 Masson 6 in 1932 was the first to consider the "triton" tumor as a separate entity. Since this first report, 27 more cases have been published in the literature. 2 Patients with the malignant form of "triton" tumor have a very poor prognosis with a rapid fatal course] These neoplasms are usually associated with von Recklinghausen's disease. On the other hand, a benign form of the "triton" tumor composed of mature nerve fibers and well-differentiated skeletal muscle fibers rarely occurs in peripheral nerves. This neoplasm is even rarer than the malignant variety. J. Neurosurg. / Volume 75 / November, 1991
Neuromuscular hamartoma of brachial plexus Clinical Aspects of Benign "Triton'" Tumors Only seven cases of neuromuscular benign "triton" tumors have been reported in the literature, z'2'4'5 The patients were four boys and three girls; all were diagnosed within the first 5 years of life, and three tumors were present at birth. All seven patients presented with a mass, but only one had any neurological deficit at presentation? None of the patients had any evidence of von Recklinghausen's disease. The tumors were located in the brachial plexus in four cases, sciatic nerve in two cases, and the median nerve in one case. Microscopically, the tumors were composed of nerve fibers and mature striated muscle. Two patients had resection of the tumor with subsequent recurrent masses in the same area, which on reexploration consisted only of dense fibrous tissue. Postoperatively, one of these patients developed paresis of the involved nerves that gradually improved over 4 years. One patient had three recurrences of the mass; the diagnosis of neuromuscular choristoma (hamartoma) was made after resection of the third recurrence. This patient presented at the age of 14 years with marked atrophy of the fight arm and absence of movement about the shoulder. A right forequarter amputation with resection of the first rib and exploration of the thoracic inlet were performed in this patient at the third recurrence? Another patient with a left brachial plexus tumor had a 90% resection. Postoperatively, this patient developed a nearly complete and permanent paralysis of the left arm with sparing of flexor muscles of the hand.t The only patient who presented with a neurological deficit had a partial tumor resection and was lost to follow-up reviewJ Of the remaining two patients, one underwent a biopsy and one a partial resection. The biopsy resulted in nerve paresis, which gradually improved. Tumors in these two cases regressed in 1 and 3 years, respectively. 4 Our patient is similar to the above cases in that there was presentation at birth with a palpable mass and no neurological deficits. A review of the slides from the original biopsy in 1954 revealed a mixture of fibrous tissue and skeletal muscle without any evidence of nerve fibers. It is our presumption, however, that the original mass had areas with the morphological appearance of a neuromuscular hamartoma. The tumor in our patient did not regress spontaneously after partial resection; instead it proliferated to a large size over a period of 35 years. This fact could argue against conservative surgical management (biopsy or partial resection) of these nerve tumors as suggested by Chen. 2 Complete resection of this neoplasm might be at-
J. Neurosurg. / Volume 75 /November, 1991
tempted at the initial presentation to prevent future neurological deficits and related deformities.
Histogenesis. The histogenesis of benign "triton" tumors remains unclear. Louhimo and Rapola 4 suggested that these tumors could arise in a peripheral nerve as a result of incorporation of the limb mesenchymal tissue within the nerve sheaths as the embryonic nerves extended peripherally and became ensheathed by neurilemma. On the other hand, mesodermal-like tissue can derive directly from neuroectodermal cells. 5 Masson 6 used this hypothesis to explain the histogenesis of malignant "triton" tumors; he believed that the neoplastic Schwann cells could transform into striated muscles. This concept is in accord with the theory of ectodermal origin of meningeal mesenchyme, embryogenesis of iris muscles from the eye cup, occurrence of primary rhabdomyosarcomas in the iris and cerebellum, and rhabdomyosarcomatous elements in medulloblastomas and medulloepitheliomas. 5 Conclusions
Neuromuscular hamartomas (choristomas) or benign "triton" tumors represent a distinct group of slowgrowing peripheral-nerve tumors with a good long-term prognosis and unclear histogenesis, These tumors may continue to proliferate over many years if left untreated. References
1. Bonneau R, Brochu P: Neuromuscular choristoma. A clinicopathologic study of two cases, Am J Surg Pathol 7:521-528, 1983 2. Chen KTK: Neuromuscular hamartoma. J Surg Oncol 26:158-160, 1984 3. Dewit L, Albus-Lntter CE, de Jong ASH, et al: Malignant schwannoma with a rhabdomyoblasfic component, a socalled triton tumor. A clinicopathologic study. Cancer 58: 1350-1356, 1986 4. Louhimo I, Rapola J: lntraneural muscular hamartoma: rel~ort of two cases in small children. J Pediatr Surg 7: 696-699, 1972 5. Markel SF, Enzinger FM: Neuromuscular hamartomaa benign "triton tumor" composed of mature neural and striated muscle elements. Cancer 49:140-144, 1982 6. Masson P: Recklinghausen's neurofibromatosis, sensory neuromas and motor neuromas, in: Contributions to the Medical Sciences in Honor of Dr. Emannel Libman. New York: International Press, 1932, Vol 2, pp 793-802 Manuscript received January 2, 1991. Accepted in final form April 30, 1991. Address reprint requests to: Deepak Awasthi, M.D., Department of Neurosurgery, Louisiana State University Medical Center, 1542 Tulane Avenue, New Orleans, Louisiana 70112.
797
