Cellular schwannoma. A clinicopathologic study of 57 patients and 58 tumors.

The cellular schwannoma is a variety of schwannoma with a predominantly cellular growth but no Verocay bodies. Because doubt has been raised about the original assessment of this tumor as benign, the clinical and pathologic characteristics of 58 cellular schwannomas from 57 patients were reviewed. The patients were most often middle aged (63% were female), and their tumors most commonly were painless masses with a predilection for the paravertebral region of the retroperitoneum, pelvis, and mediastinum. Most tumors were solitary and encapsulated, and an associated nerve was identified for 43% of the cases. Electron microscopic and immunohistochemistry studies confirmed the tumor's Schwann cell nature. Worrisome features such as bone erosion, hypercellularity, foci of necrosis (four tumors), hyperchromasia, nuclear pleomorphism, and the presence of mitotic figures led to a malignant diagnosis for 28% of the cases. Treatment in all but one case was surgical excision. Two patients also received radiation therapy and chemotherapy. Follow-up of from 1 year to 24 years, 7 months (median of 6 years and mean of 7 years) for 61% (35 cases) of the cases reveals three patients with a local recurrence but no cases in which the tumor metastasized or the patient died of the tumor. Awareness of this tumor type is important so that the surgeon will avoid unnecessary sacrifice of functionally important nerves attached to these tumors and so that needless adjuvant radiation and chemotherapy will not be instituted.