Malignant Triton Tumor of the Retroperitoneum in an Infant: Case
report and Review of the Literature
Zhibin Hou1,M.D, Mohamed Nasar Chemban2,MBBS, Xin Li1,M.D, Xiaoli Hu3,M.D, Chunxiang Wang1,M.D, Chunquan Cai4,PhD
1.
Department of Radiology, Tianjin Children Hospital, No. 238 Longyan Road, Beichen District, Tianjin, P. R. China 300401
2.
Graduate College of Tianjin Medical University , No. 22 Qixiangtai Road, Heping District, Tianjin, P. R. China 300070
3.
Department of Pathology, Tianjin Children Hospital, No. 238 Longyan Road, Beichen District, Tianjin, P. R. China 300401
4.
Department of Surgery, Tianjin Children Hospital, No. 238 Longyan Road, Beichen District, Tianjin, P. R. China 300401
Corresponding author: Chunquan Cai , Tel: 18522008608, e-mail: [email protected]
Abstract: Malignant triton tumor (MTT) is a very rare subtype of malignant peripheral nerve
sheath tumors (MPNST), a histological variation of MPNST with additional rhabdomyoblastic
elements. This rare tumor usually affects adult patients with neurofibromatosis-1 (NF-1, About
50% of cases). Here we are reporting a case of a female infant aged 8 months, who presented
with a large mass at the lower abdomen and pelvis. Finally it was diagnosed by immuno-staining
with S-100 protein and myogenin. MTT has a poor prognosis owing to its aggressiveness in
biological behavior. The fact that this tumor occur in infants are extremely rare, so it has
prompted us to report this case.
Key words: Malignant triton tumor (MTT); infant; Retroperitoneum; S-100 protein;
Introduction: MTT is a histological variation of MPNST with additional rhabdomyoblastic
elements accounts for about 5-10 % of all soft tissue sarcomas[1]. The common sites affecting
MTT are the head, neck, extremities and trunk. Other parts such as buttocks, the mediastinum
and the retroperitoneum are less common [2-3]. MTT occur in the retroperitoneum are extremely
rare, which is as much few as only 10 cases have been reported since 1984[4]. Here the case we
are reporting about an 8-month-old girl infant with a huge mass in the abdomen. The imaging,
histo-pathologic examinations, treatment and prognosis findings of MTT are also reviewed.
Case presentation: An 8-month-old female infant who was admitted to our hospital with a
history of founding an abdominal mass by ultrasound scan 2 weeks ago. The physical
examination revealed a firm mass which has no tenderness, well-defined and could be touchable
through the lower abdomen. It was a low echo and solid mass on abdominal ultrasound, with
punctiform blood flow on CDI. The laboratory examination shown the WBC -18.8×109/L, HCG
-78g/L, serum creatinine was within normal limits and Alpha-fetoprotein (AFP) was weakly
positive. There were no signs of neurofibromatosis type 1(NF-1).
Magnetic resonance imaging of the abdomen T1-weighted image showed a hypointensity mass
in the retro-peritoneum and pelvis measuring 14cm×12cm×9cm (Fig. 1). The mass
heterogeneously turned hyperintense on T2-weighted images (Fig. 2). After intravenous contrast
medium (Gd-DTPA), the mass found as inhomogeneous enhancement on coronal image (Fig. 3).
Non-enhanced area suggested cystic changes or necrosis. A great mass which originated from
the left iliac fossae and extended to the retroperitoneum was seen. And then took out the mass by
a surgical resection. Local hemorrhages, the left ovary, body of uterus were also be involved, so
all these also excised meanwhile.
On gross examination, the excised mass which measured about 16 cm× 15.8 cm × 6.6 cm
consisted of a large globular gray tumor. The surface was smooth, and the cut surface appeared
solid tenacity gray-white with weaves of tenacity hemorrhage and there was semitransparent in
focal areas (Fig. 5A). Microscopically, it revealed alternating hypocellular and hypercellular
regions composed of spindle and polygon cells with the pathological karyokinesis and striated
muscle differentiation. The nucleus of polygon cells were large , hyperchromasia and abundant
hyalomitome. On further investigations immunohistochemical stains showed malignant cells
were positive for S-100 protein, Desmin and NF (Fig.5B-D). The malignant cells were negative
for smooth muscle actin (SMA) and Actin. These immunohistologic findings established the
diagnosis of MTT. However, two months after the operation, the patient was readmitted by
complaining abdominal distention and diarrhea of 2 weeks. The enhanced CT imaging on
coronal plane revealed multiple low density masses were fully filled in the abdomen and pelvis,
and those were also enhanced slightly(Fig. 4). After Combining with history we considered it as
the recurrence and metastasis. The parents of the infant decided to give up, and no subsequent
treatment was undertaken.
Discussion: The MPNST with rhabdomyosarcomatous differentiation was first described by
Masson in 1932, but the term “malignant triton tumor” (MTT) was not named until 1973 by
Woodruff who specified the following diagnostic criteria: criteria no.1: the tumor arises along
the course of a peripheral nerve or in a location typical for peripheral nerve tumors or in a patient
with NF-1 disease; criteria no.2: the dominant population consists of cells with the same growth
traits as Schwann cells; criteria no.3: rhabdomyoblasts are present and originate from the body of
the peripheral nerve tumor and which cannot be traced to either an extension or metastasis from
an extrinsic rhabdomyosarcoma [5].
MTT is a very rare subtype of MPNST, a histological variation of malignant peripheral
nerve sheath tumor with additional rhabdomyoblastic elements. The origin of MTT remains
unclear, although the presence of neural cells and rhabdomyoblasts has lead more authors to
presume that these two cell components are derived from less differentiated neural crest cells.
These cells have high potential ability to develop skeletal and neural components[6].
MTT constitutes about 5% of all MPNSTs and are usually presented as a painful or painless
firm enlarging mass in a variety of locations including the head, neck, extremities and trunk. And
other parts such as the buttocks, the mediastinum and the retro-peritoneum were less common
sites[2-4]. MTT happens in two principal forms: sporadic or in conjunction with NF-1. MTT
associated with NF-1 is in about Two third of all cases, which diagnosed at a younger age and
predominantly occuring in males. The contrary sporadic forms are seen in older age groups with
an equal sex distribution.
Overall the 5-year survival rate of MTT is lower than 15% in contrast to MPNST in both
groups. The local recurrence rate is about 40% and metastases occur in about 50% [7-9]. The main
factors affecting survival are likely to be associated with the location of the tumor and the extent
of the excision. MTT arising in head, neck or extremity survives longer than those in the
buttocks, trunk or retroperitoneum[10].
MTTs are more aggressive than typical malignant nerve sheath tumors and follow a natural
course consonant with high grade sarcomas. Complete surgical resection is the mainstay of
treatment with adjuvant radiotherapy, being used often to consolidate local disease control. Up to
date, MTT occurs in the retroperitoneum are extremely rare, which is only less than ten cases
reported in the English literature using PUBMED [3,7,9,11].
Combined with former literatures, we summarize the MTT of retro-peritoneum also has
some characteristics such as:
1.The tumor can occur in any age ,but the infant case is very rare;
2.The ratio of incidence in male and female is about 1:1;
3.It occurs in about 50% of patients with NF-1;
4.The tumor located in the retro-peritoneum is often huge (more than 7 cm in diameter) and
involved of the adjacent organs;
5.After completly excision, the tumor is metastasized and recurred is present in about 90% of
patients. In fact, the location, large size, and the stage of tumor are all found to affect survival
[3,9,11-12]
.
The diagnosis of MTT is usually certified by immunohistochemical staining supported by
positivity for S-100 protein and Leu-7 (CD57), whereas rhabdomyoblastic differentiation is
confirmed by positivity to desmin, actin and myogenin[13,14]. But now, the neoplasm which is
positive for S-100, desmin and myogenin indicated nerve sheath and rhabdomyoblastic
components[12]. The morphological features in Microscopy are alternating hypocellular and
hypercellular regions, the appearance of thin wavy comma-shaped/bullet-shaped nucleus in the
hypocellular areas, presence of nuclear palisading, prominent thick-walled vasculature, and
presence of rhabdomyoblasts[15]. The imaging studies of MTT, such as ultrasonography, MSCT
or MRI is not met the specificity in diagnosing, but it has the value of distincting the extension of
the tumor, the involvement of the adjacent organs, whether metastasis present or not in other
parts, and the grade of the tumor. This is important to perform the surgical resection. Due to the
worse prognosis, higher rates of metastasis and earlier recurrent rates, some studies suggest that
complete surgical resection combined with adjuvant radiotherapy should be the gold standard
treatment for MTT at present[16,17]. Although the role of adjuvant therapy has not been proven
yet to be effective, it may prolong the survival [18].
Conflict of Interests: The authors declare that there is no conflict of interests regarding the
publication of this paper other than sharing the rare case in the literature which may help to those
who are in need.
References:
1.Weiss SW, Goldblum JR. Malignant tumors of peripheral nerves. Enzinger and Weiss’s soft
tissue tumors, 5th edn. Mosby Elsevier, China, 2008,903-944.
2.Yakulis R, Manack L, Murphy AI, et al.Postradiation malignant triton tumor. A case report and
review of the literature. Arch Pathol Lab Med,1996,120:541-548.
3.Masson
P,Recklinghausen’s
neurofibromatosis.Sensory
Neuromas
and
Motor
Neuromas.Libman
Anniversary.2 vol.New York,International Press,1932,793-802.
4.Suresh TN, Harendra Kumar ML, Prasad CS, et al, Malignant peripheral nerve sheath tumors
with divergent differentiation. Indian J Pathol Microbiol. 2009,52(1):74-76.
5.Woodruff JM,Chernik NL,Smith MC,et al. Peripheral nerve tumors with
rhabdomyosarcomatous
differentiation (malignant 'triton' tumors).Cancer,1973,32(2):426-439.
6. Zhiwei L, Xiang J, Yan S, et al.Malignant triton tumor of the retroperitoneum: a case report
and review of the literature.World Journal of Surgical Oncology 2012;30(10):96.
7.Koutsopoulos AV, Mantadakis E, Katzilakis N,et al.Long-term survival of a patient with a
neurofibromatosis Type-1 associated retroperitoneal malignant triton tumor after multimodality treatment. Clin Neuropathol,2011,30(6):333-5.
8.Shetty PK,Baliga SV,Balaiah K. Malignant Triton Tumor: A Rare Case. Indian J Surg,
2013,75(Suppl 1):362-365.
9.Aldlyami E, Dramis A, Grimer RJ et al Malignant triton tumor of the thigh a retrospective
analysis of nine cases. Eur J Surg Oncol. 2006,32(7):808-10.
10.Terzic A, Bode B, Gratz KW, et al. Prognostic factors for the malignant triton tumor of the
head and neck. Head Neck.2009,31(5):679-88.
11.Hoshimoto S, Morise Z, Takeura C,et al.Malignant Triton tumor in the retroperitoneal space
associated with neurofibromatosis type 1: a case study. Rare Tumors. 2009,28;1(2):e27.
12.C.-C.H,Stucky,K.N.Johnson,R.J.Gray,et
al.Malignant
peripheral
nerve
sheath
tumors(MPNST): the Mayo
Clinic experience. Ann Surg Oncol. 2012,19(3):878-85.
13.Brooks JS,Freeman M,Enterline HT. Malignant triton tumors:natural history and
immunohisto- Chemistry
of nine new cases with literature review.Cancer,1985,55(11):2543-9.
14. Brooks JSJ. Disorders of soft tissue. In: Sternberg SS (ed) Diagnostic surgical pathology, 3rd
edn. Lipincott Williams and Wilkins, Philadelphia, 1999,131–221.
15.Woodruff JM,Perino G.Non-germ-cell or teratomatous malignant tumors showing additional
rhabdomyobl
-astic differentiation, with emphasis on the malignant Triton tumor, Semin Diagn Pathol,
1994,11(1):69-81.
16.McConnell YJ,Giacomantonia CA. Malignant triton tumors-complete surgical resection and
surgical
resection and adjuvant radiotherapy associated with improved survival. J Surg Oncol.106
(1):51-56.
17.Nitsche M, Reible M, Pflüger KH,et al. Malignant Triton Tumor of the Sciatic Nerve as a
Secondary Malignancy after Extended Field Radiotherapy and Chemotherapy of Hodgkin’s
Disease, Case Rep Oncol,2014,28;7(1):239-45.
18.Omar T, Raslan H, El Sheikh S,et al. Low-Grade Malignant Triton Tumor of the Neck: A Case
Report and Review of the Literature, Case Rep Pathol.,2014,9(22):1-5.
Figure1-2 Axial view of MR showing a long T1 and long T2 huge tumor occupying the entire retroperitoneal space ,
the signal inside the tumor was not uniform and the intestinal canals were compressed
Figure 3. Coronal view of enhanced MR showing the rim of the tumor was enhanced markedly ,and the inner was
not. the right adnexa uteri may be involved. Figure 4. Coronal view of abdominal computed tomography 2 months
after the completely excised revealed the presence of recurrence and enlargement .
A
图 5 大体标本
C
B
免疫组化 NF（＋）
D
Figure 5A. The excised specimen(16cm×15.8cm×6.6cm). Images of immunohistochemical staining showing the
following: 5B.Neurofilament Protein(+),Large pleomorphic rhabdomyoblastic cells with abundant eosinophilic
cytoplasm are embedded in a spindle cell tumor with a fine fibrillary matrix(Original magnification 200×) 5C.
Diffuse positivity for S-100 protein(200×). 5D.Desmin was positive in the rhabdomyoblast cells (200×)