Spontaneous Radial Nerve Palsy due to an Unrecognized Myofibroma: A Case Report.

CASE: A 33-year-old woman presented with a six-month history of spontaneous radial nerve palsy and no identified lesion on imaging. She underwent operative exploration where an hourglass deformity was seen and resected. Pathology returned as a rare tumor, a myofibroma. The patient regained full radial nerve function. CONCLUSIONS: A trial of observation is often indicated in the cases of isolated nerve palsy where anatomic lesions have been eliminated. This case highlights that imaging studies can miss a tumor involving nerve and that painless, spontaneous nerve palsy may be a time where early surgical intervention offers a better chance of recovery.

Solitary myofibroma of the mandible: an immunohistochemical and ultrastructural study with a review of the literature.

A solitary myofibroma (MF) is an unusual spindle cell neoplasm that usually arises in the soft tissue, skin, or bone of the head and neck region in infancy. We report an extremely rare case of MF of the mandible in an 18-year-old Japanese woman together with the conventional histologic, immunohistochemical, and electron microscopic findings. The tumor was well circumscribed and composed of fibroblast-like or myofibroblast-like spindle cells. On immunohistochemical evaluation the tumor cells were positive for vimentin, α-smooth muscle actin, HHF-35, and calponin, but negative for neurogenic antigens and markers for vascular endothelial cells. The Ki-67 labeling index was 10 % and the p53 labeling index was 10 %. Ultrastructural examination revealed smooth muscle cell differentiation. The patient was treated by surgical resection and underwent follow-up without any signs of recurrence. MF presents a wide range of differential diagnosis, including benign and malignant neoplasms. Therefore, accurate diagnosis may avoid an unnecessarily aggressive therapy.

Malignant myopericytoma-like tumor in a Fischer rat.

Myopericytoma is a perivascular tumor that has been recently described in humans, but not in laboratory rodents. The authors encountered an intra-abdominal tumor resembling human malignant myopericytoma in a Fischer rat. Grossly, the tumor was found as two brown-colored masses located in the mesentery of rectum. Microscopically, the tumor was composed of oval to spindle-shaped cells, which were arranged in sheets around numerous thin-walled branching vessels and partly showed a concentric perivascular growth pattern. Mitoses were frequently seen, and the tumor cells showed a local invasion. Immunohistochemically, the tumor cells were strongly positive for alpha-smooth muscle actin and weakly positive for vimentin and desmin. Ultrastructurally, the tumor cells had dendritic processes, actin-like thin filaments with dense bodies, basement membranes, hemidesmosomes, and micropinocytotic vesicles. These findings suggest that the most appropriate term for diagnosis of the present case could be a malignant myopericytoma.

The spectrum of pediatric fibroblastic and myofibroblastic tumors.

Fibroblastic and myofibroblastic tumors in neonates, infants, and children provide a diagnostic dilemma in surgical pathology due to their relative rarity and similarity in appearances. These tumors may be congenital or occur early during the first years of life or later during the first and second decades of life. The morphologic, immunocytochemical, ultrastructural, cytogenetic, and molecular features of the more "common" pediatric fibroblastic and myofibroblastic tumors are reviewed. In addition, the importance of a multimodal approach to tumor diagnosis is emphasized, with correlation with treatment and outcome differences among these unique fibroblastic and myofibroblastic tumors. The importance of providing an accurate diagnosis with pediatric fibroblastic and myofibroblastic tumors cannot be overstated, because treatment, prognosis, follow-up, and outcome are based on the initial assessment of these fascinating, but oftentimes, perplexing tumors.