Hepatic metastasis with heterologous rhabdomyoblastic differentiation in a patient with gastrointestinal stromal tumor treated with imatinib.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the intestinal tract. In patients with locally advanced and/or metastatic GIST, the introduction of tyrosine kinase inhibitor, imatinib mesylate, has transformed the management of this previously untreatable neoplasm into a treatable entity. Approximately 80% of advanced metastatic GISTs respond to imatinib treatment. However, the majority of patients suffer disease progression at a median of 2 years due to drug resistance. Generally progressing GISTs retain their typical morphology. Herein, we report an extremely rare case of progressive metastatic GIST with heterologous rhabdomyoblastic differentiation after, imatinib mesylate treatment. We also review the relevant literature.

Pulmonary Blastoma with Rhabdomyoblastic Differentiation: A case report with immunohistochemical and electron microscopic examination

Pulmonary blastoma is a rare lung tumor composed of epithelial and mesenchymal element : the latter element may show various pattern of differentiation toward mature tissue, such as cartilage, smooth muscle, and bone. Rhabdomyoblastic differentiation in pulmonary blastoma is quire rare. In th literature, only seven cases have been reported. We report a case of pulmonary blastoma with rhabdomyoblastic differentiation which occured in a 3 year old girl. Microscopically, cytoplasmic cross-striation was present. Immunohistochemically, strong positivity for vimentin and desmin was observed. Electron microscopy demonstrated A and I bands which documented rhabdomyoblastic differentiation.