Clinicopathologic Study of Ectomesenchymomas from Intergroup Rhabdomyosarcoma Study Groups III and IV |
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Authors: | Daniel R Boué David M Parham Bruce Webber William M Crist Stephen J Qualman |
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Institution: | (1) Department of Laboratory Medicine and IRSG Pathology Center, Children's Hospital and Ohio State University School of Medicine, 700 Children's Drive, Columbus, OH 43205, USA, US;(2) Department of Pediatric Pathology, Arkansas Children's Hospital, University of Arkansas–Medical School, 800 Marshall Street, Little Rock, AR 72202, USA, US;(3) Department of Pathology, Baptist Memorial Hospital, 899 Madison Avenue, Memphis, TN 38146, USA, US;(4) Department of Pediatric and Adolescent Medicine, Mayo Clinic, Desk East 9 (PEDS), 200 First Street SW, Rochester, MN 55905, USA, US |
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Abstract: | Ectomesenchymomas (EM) are rare malignant neoplasms usually consisting of rhabdomyosarcoma (RMS) with a neural component.
Only 21 cases have been previously reported. Here we extend the clinicopathologic spectrum of EM by describing our findings
in 15 cases. Only 5 patients were infants; 10 were ≤3 years old and 5 were ≥6 years old. No male predilection was observed;
7 were female. The originating institutional diagnoses were; RMS (12), undifferentiated sarcoma (1), or EM (2), suggesting
underdiagnosis of this entity. The primary tumor sites included external genital (5), pelvis/abdomen (6), head and neck (3),
and extremity (1). The size of the primary neoplasm was usually ≥5 cm at diagnosis but dissemination only occurred in a minority.
Local infiltration was not uncommon. These neoplasms were typically multilobate, thinly encapsulated, hemorrhagic, and necrotic.
Light microscopic features were highly variable, but embryonal RMS with scattered or clustered ganglion cells, often in lacunae,
was characteristic. In some cases, primitive neuroblastic or neuroectodermal areas were found and/or a component of alveolar
RMS was seen. Focal anaplasia was occasionally observed. Mitotic activity appears higher than previously appreciated and some
necrosis was invariably present. Electron microscopy was performed in 11 cases, which confirmed skeletal muscle ± neural differentiation.
Cytogenetic studies performed in five cases revealed no specific abnormality. Monoclonal neuron-specific enolase was the best
marker of ganglion cells and primitive neural elements. MIC-2 (CD99) membrane expression was not definitively present in any
of the six cases examined. A number of the above parameters appear to be of some prognostic significance, but overall, these
neoplasms appear to have a similar outcome as would be predicted for their RMS element alone (exclusive of any neural component),
with respect to the RMS subtype, age of the patient, and anatomic location of the neoplasm. |
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Keywords: | : ectomesenchymoma malignancy neuroectodermal/neuroblastic rhabdomyosarcoma |
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