Adenoid Cystic Carcinoma of the Skull Base: Immunohistological Characteristics and Correlation to Clinical Behavior

Introduction: ACC characteristics have an unpredictable progression, especially in the skull base. Involvement of intracranial structures and recurrences can take place even decades after primary treatment. This study compares different surgical strategies and tools for ACC of the anterior and posterior skull base with a focus on corresponding immunohistological markers of these individual tumors.

Material and Methods: This study covered 31 patients with ACC involving the base of skull. Clinical findings, surgical strategy, and postoperative outcome were examined. The average follow-up is 21 months (range: 2–62). For immunohistological examination we used Ki-67, PCNA, p-53, p-63, p-73, and bcl-2 Oncoproteine.

Results: Twenty-eight of 31 ACC were localized in the anterior skull base. The majority of the tumors were staged as T2 or higher. In 12/31 patients. regional metastases were detected. Six of 31 patients were staged as M1. Of 31 patients, 28 were treated surgically; 19 of 31 patients had combined radio/chemotherapy. The overall recurrence rate in a medium follow-up of 21 months was 34%. A significantly better rate of complete remission was found in the group who underwent radical surgery. There are significant correlations with histological differentiation and rate of metastasis of ACC. P-73 and Bcl-2 seem to be useful for diffentiation-index in addition to the G-System.

Conclusions: ACC is still incurable. In skull base surgery the treatment is made more difficult because of the narrow topography available to access functional essential structures. A clinical-immunhistological grading system may allow a more individual treatment strategy.