A rare case of malignant fibrous histiocytoma of the gingiva

BACKGROUND

Malignant fibrous histiocytoma (MFH) is an aggressive, high-grade tumor with poor prognosis. It is the most common soft tissue sarcoma in adults, usually occurring retroperitoneally in extremities. MFH of the head and neck is rare. Cases with primary involvement of only the oral soft tissues have been reported; a few occurred in the gingiva. Its clinical features include a painless enlarging mass, which may or may not be ulcerated.

METHODS

A 20-year-old female patient presented with a non-healing necrotic ulceration of 4 months' duration on the maxillary anterior labial gingiva. Based on her history and agricultural background, a provisional diagnosis of chronic fungal and chronic bacterial infection was given. The patient was placed on a topical antifungal in combination with antibiotic therapy for 10 days. Because the lesion failed to respond to the initial therapy, an incisional biopsy was performed. The lesion was diagnosed as MFH based on clinical, histopathologic, and immunohistochemical findings.

RESULTS

The patient was referred to the Department of Oncology and Oral and Maxillofacial Surgery, Manipal College of Dental Sciences, Manipal, for further evaluation and treatment; the lesion was treated by resection of the premaxilla, and a splint was placed. She was followed up for 3 months with improvement in her condition.

CONCLUSIONS

Because MFH is rare in the oral cavity, misdiagnosis may not be unusual based on the initial clinical examination. Any suspicious lesion that is unresponsive to treatment must be subjected to histopathologic evaluation to arrive at a final diagnosis.

Three-dimensional spiraling finite element model of the electrically stimulated cochlea

OBJECTIVE

The objective of the article is to provide an accurate model of the human cochlea with which potential distributions and thus neural excitation patterns around cochlear implant electrodes can be determined. Improvements on previous models of the implanted cochlea are that this model 1) includes the spiral nature of the cochlea as well as many other anatomical details (and it is a model of the human cochlear rather than the guinea pig cochlea), and 2) facilitates modeling of different electrode geometries, array locations and electrode separations without changing the structure of the model.

DESIGN

A three-dimensional spiraling finite element model of the human cochlea was created. The model incorporates the effect of neighboring canals and conduction along the fluid-filled canals of the cochlea. Potential distributions are used as inputs to a nerve fiber model to investigate auditory nerve excitation patterns around intracochlear electrode arrays.

RESULTS

Potential distributions around intracochlear electrodes generated with the finite element model are presented. The effects of electrode separation, electrode geometry and array location on excitation threshold, excitation spread and ectopic excitation (i.e., excitation of nerve fibers at an undesirable location) are demonstrated.

CONCLUSIONS

The following conclusions should be considered preliminary, as their accuracy depends on the exactness of the underlying model. The spiraling geometry of the cochlea causes asymmetry in potential distributions. The location of electrodes along the length of the basilar membrane has a stronger influence on the site of excitation than the polarity of the leading phase of the stimulus. Array location is the primary parameter that controls excitation spread. Threshold currents and the effect of ongoing loss of peripheral dendrites on threshold currents can be limited by placing arrays close to the modiolus. Point electrode geometries are recommended above banded electrode geometries only when the array can be placed close to the modiolus. There is a tradeoff between array location and the degree of ectopic stimulation caused by a specific array location. Bimodal excitation patterns exist at comfortable stimulus intensities for longitudinal bipolar electrode configurations. It is shown that an electrode configuration with an electrode separation of approximately half that of the bipolar electrode separation of the Nucleus electrode can be used instead of radial and offset radial electrode configurations to create unimodal excitation patterns. The stimulation resolution of cochlear implant electrode arrays can potentially be improved by increasing the number of electrode contacts in an array.

Malignant fibrous histiocytoma of the oral soft tissues

Between 1944 and 1984, six patients with a malignant fibrous histiocytoma of the oral soft tissues were treated at the M.D. Anderson Hospital and Tumor Institute. From the time of the first description of this tumor until 1984, another 10 documented cases of malignant fibrous histiocytoma involving the oral soft tissues were reported in the English-language literature. With respect to these 16 patients (including our 6 cases), the clinicopathologic aspects of malignant fibrous histiocytoma, treatment, and survival figures are discussed. The treatment of choice is early and radical surgery, including neck dissection, since in four of the six patients treated at the M.D. Anderson Hospital and Tumor Institute regional lymph node metastases were found. The response to chemotherapy, except for the response of patients with the inflammatory type of malignant fibrous histiocytoma, and radiotherapy is usually poor. The 2-, 3-, and 5-year survival rates respectively, are, 36%, 30%, and 20%.