Clinicopathological Study of Undifferentiated Carcinoma of the Parotid Gland

Objective: Undifferentiated carcinoma of the salivary gland is a rare malignant tumor, and is difficult to distinguish from other poorly differentiated types of carcinoma or sarcoma. The present study investigated clinical and pathological characteristics for undifferentiated carcinoma of the parotid gland.

Patients And Methods: Forty-four patients with previously untreated carcinoma of the major salivary glands were treated at our institution between 1986 and 1999. Of these, five patients (two males, three females) were diagnosed with undifferentiated carcinoma of the parotid gland and treated. For histological reinvestigation, multislices of resected specimens were made and diagnosed.

Results: Although all patients were treated by radical surgery (more than subtotal parotidectomy), all died of distant metastasis, including two patients with locoregional relapse. Tumors in these two patients included a small portion of poorly differentiated epidermoid or mucoepidermoid carcinoma. The remaining three patients did not show any differentiated portions, and histological findings demonstrated heterogeneous patterns of lymphoepithelial carcinoma, small cell carcinoma and unclassified (a pattern of malignant hemangiopericytoma), respectively.

Conclusions: Investigation using multislice sections is needed to diagnose undifferentiated carcinoma of the salivary glands. Regarding prognosis, carcinoma that is too poorly differentiated but including slightly-differentiated portions should be considered undifferentiated carcinoma. All patients died of distant metastasis despite radical surgery, suggesting that chemotherapy is needed to improve patient outcomes.