Indian Journal of Pathology and Microbiology

: 2010  |  Volume : 53  |  Issue : 1  |  Page : 192--193

Retroperitoneal ectomesenchymoma: A rare childhood tumor

Sheenu Misra, Nuzhat Husain 
 Department of Pathology, CSM Medical University, Lucknow, India

Correspondence Address:
Nuzhat Husain
Department of Pathology, CSM (Erstwhile King George«SQ»s medical University), Lucknow-226 003

How to cite this article:
Misra S, Husain N. Retroperitoneal ectomesenchymoma: A rare childhood tumor.Indian J Pathol Microbiol 2010;53:192-193

How to cite this URL:
Misra S, Husain N. Retroperitoneal ectomesenchymoma: A rare childhood tumor. Indian J Pathol Microbiol [serial online] 2010 [cited 2021 Jan 28 ];53:192-193
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Ectomesenchymoma is a rare malignant tumor that may arise in the brain or soft tissue. It is characterized by both neuroectodermal and mesenchymal components including rhabdomyosarcoma, liposarcoma, malignant fibrous histiocytoma, leiomyosarcoma, chondrosarcoma, malignant peripheral nerve sheath tumor and osseous elements. In children an embryonal rhabdomyosarcoma has been observed more frequently. We present a rare case of childhood ectomesenchymoma in which the mesenchymal component was a pleomorphic rhabdomyosarcoma.

A three-year-old female child presented with a retroperitoneal mass. Excised specimen measured 22 x 14 x 12 cm. The outer surface was well circumscribed, lobular and white with a pseudo capsule at the advancing edge. The cut surface showed a firm fibrillar mass with small foci of hemorrhage and necrosis. Histological evaluation showed a pleomorphic spindle cell sarcoma with rhabdomyoblasts. Several large bizarre pleomorphic giant cells as well as ganglion-like cells with large round vesicular nuclei and prominent nucleoli were seen. The tumor was richly vascular with peritumoral invasion. Mitoses were frequent. Dual marker expression was observed in immunohistochemistry with a positive desmin stain in rhabdomyoblasts, giant cells and spindle cells and synaptophysin expression in ganglion cells as well as tumor giant cells [Figure 1] a-d. Overall staining for both antigens was high and it appeared that a fair number of cells were expressing both antigens. A diagnosis of ectomesenchymoma was made. The neural component in ectomesenchymoma may be composed of neuroblasts and/ or ganglion cells and range from well differentiated neuroblastic cells (neuroblastoma, ganglioneuroblastoma, ganglioneuroma) to peripheral neuroectodermal tumors. [1] It has been postulated that this lesion results from a biphenotypic expression in tumor cells. Some authors classify this tumor with the peripheral nerve neoplasms but others postulate that it is a rhabdomyosarcoma with neuronal differentiation. [2]

We report our observations to emphasize the need for IHC in morphologically classic rhabdomyosarcomas. The neural component of ectomesenchymoma can be frequently overlooked. Large round cells with vesicular chromatin and prominent nucleoli prompted us to suspect a mixed lesion. It may be impossible to exclude ectomesenchymoma in limited material such as needle core biopsy or small incisional biopsy. [3] The differential diagnosis includes mainly teratoma, Wilm's tumor, benign and malignant triton tumors and other collision tumors. [1]

Due to the comparatively small numbers reported in the literature, accurate information on biological behavior is lacking. However, the lesion appears to essentially behave as the most malignant of the mesenchymal elements. Chemotherapy and complete surgical excision are the treatments of choice.


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