Cell necrosis and endocytosis (apoptosis) in an embryonal rhabdomyosarcoma of the orbit.

An orbital embryonal rhabdomyosarcoma, which was excised from the orbit of an 8-year-old girl, was studied by light microscopy and transmission electron microscopy. Cells within the tumour demonstrated by light microscopy diffuse areas of necrosis and isolated single-cell necrosis. There were many viable tumour cells with intracytoplasmic vacuolar structures which contained basophilic granules. Ultrastructural studies showed close apposition between well-preserved tumour rhabdomyoblasts and degenerate or necrotic tumour cells: degenerate cells and condensed cell fragments were observed within the cytoplasm of the well-preserved tumour cells. Some cells which showed degenerative changes had features which suggested that they had ingested more than one degenerate cell on separate occasions. This phenomenon may be regarded as a variant of selective individual cell death, currently referred to as apoptosis, which has not been previously reported in a case of embryonal rhabdomyosarcoma. The patient remains free of tumour recurrence four years following treatment with combined radiotherapy and chemotherapy.