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Presented by Pedram Argani, M.D. and prepared by Wang (Steve) Cheung, M.D., Ph.D.
Case 3: An 8 year old male with a retroperitoneal mass.
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Week 312: Case 3
An 8 year old male with a retroperitoneal mass.
Answer: Anaplastic rhabdomyosarcoma
Histology: This is a high grade neoplasm, in which the tumor cells cluster around blood vessels and undergo necrosis away from the blood vessels (peritheliomatous growth pattern). Tumor cells have hyperchromatic nuclei and variable nuclear shapes. Abnormal (tripolar or multipolar) mitoses are evident, as are tumor giant cells. These features are diagnostic of anaplasia. Tumor cells show no evidence of tubular formations, and label diffusely with desmin and for myogenin. These features are typical of rhadomyosarcoma, and the nuclear changes warrant the designation as anaplastic. This neoplasm lacked evidence of the PAX-FKHR gene fusions typically associated with alveolar rhabdomyosarcoma, and hence is best classified as an anaplastic embryonal rhabdomyosarcoma.
Discussion: Malignant lymphoma would feature more discohesive cells with more irregular nuclear contours, and thickened nuclear membranes. Primitive neuroectodermal tumor would feature primitive cells with round nuclei and evidence of rosette formations. Anaplastic Wilms tumor, metastatic to retroperitoneal lymph nodes, is a major consideration here. However, the absence of lesions within the kidney and the absence of any evidence of tubular formations within this lesion exclude that possibility. Anaplastic rhabdomyosarcoma is associated with p53 gene alterations. p53 protein expression is a good but imperfect surrogate for p53 gene mutations.
– Parham DM. Mod Pathol 2001;14:506-514.