br Discussion Benign FH is usually of two

Discussion Benign FH is usually of two types: cutaneous type and that involving deep soft tissues. Histologically, deep FH has many features in common with cutaneous cellular FH, including a storiform and/or short fascicular growth pattern, similar cytologic features with frequently limited or absent polymorphism, and increased cellularity. Deep benign FH is an under-recognized neoplasm that most commonly arises in the subcutaneous tissue of the extremities, but may occur at any soft tissue site. The most important diagnostic distinction is the separation of this tumor from the malignant type. Histopathologically, this tumor is a neoplasm of a biphasic cell population of histiocytes and fibroblasts. Diagnosis of benign FH is often difficult and usually based on immunohistochemistry. The immunohistochemistry can help in making a differential diagnosis of the soft tissue tumor. Negativity for smooth muscle GSK1324726A cost and S-100 can differentiate the lesion from leiomyosarcoma and neurogenic tumors. Gastrointestinal stromal tumors are one of the most common mesenchymal tumors of the gastrointestinal tract. Most gastrointestinal stromal tumors are c-kit positive (other possible markers include CD34, DOG-1, and desmin). In our case, the immunohistochemistry was not correlated with this criterion. Negativity for CD10, CD56, AE1/3, EMA, calretinin, alpha-inhibin, and D2-40 ruled out gynecologic lesions and that for CD21 eliminated the possibility of follicular dendritic cell sarcoma. MDM2/CDK4 is used for liposarcomas. Malignant FH is composed of malignant pleomorphic sarcomatous cells, bizarre giant cells, and frequent mitotic figures. The difference between benign and malignant FH is usually obvious, because the latter is a pleomorphic, deep-seated tumor with numerous typical and atypical mitotic figures. Gleason and Fletcher reviewed the clinicopathologic features of 69 cases of deep benign FH. The most common anatomic locations were the extremities (58%). Lesions arising in visceral soft tissue were rare. The local recurrence rate of deep benign FH was 22%, which is significantly higher than that of conventional cutaneous FH. Deep FH seems to have an increased risk of local recurrence as compared with conventional FH and also has a very low (and seemingly unpredictable) risk of distant metastasis.
Introduction
Case Report A 43-year-old female had a sudden onset of a feeling of heaviness, headache, and dizziness for 1 month. She had one fainting spell with an upward gaze. Her personal and family history was unremarkable. Mild cerebellar ataxia was noted, but she could still walk well. The brain magnetic resonance image (MRI) showed a heterogenous, popcorn-shaped mass lesion within the fourth ventricle that had an ill-defined margin with the dorsal surface of the medulla oblongata. The mass was 2 cm × 2 cm × 2 cm. The intraventricular portion of the tumor blocked the outlet of cerebrospinal fluid (CSF), which produced secondary obstructive hydrocephalus. The mass was hypointense on T2-weighted images and hyperintense on T1-weighted images with poor gadolinium (Gd) enhancement (Fig. 1A). In May 2011, she underwent surgical resection in the sitting position and by a telovelar approach. Air emboli were detected intraoperatively and the operation was discontinued temporarily. When the procedure was resumed, we found that the tumor had low vascularity and was fragile, but it had infiltrated into the dorsal surface of the medulla oblongata (Fig. 2A). A gross total tumor removal was achieved, although the margin of the tumor could not be distinguished from the floor of the fourth ventricle. The cerebrospinal fluid (CSF) pathway was reopened and the structure of the fourth ventricle was clearly evident after removing the tumor. Intraoperative mapping guided the operator to locate the nucleus of cranial nerve (CN) 12 just behind the tumor, and helped the operator find the intact nuclei of CN7, CN8, and CN11 (i.e., the nucleus ambiguus) during the operation (Fig. 2B). The motor evoked potentials (MEPs) of the CN were within the normal range during the whole procedure. The operation was smoothly performed. The patient awoke without any CN deficits.