Role of Volumetric Modulated Arc Technique Radiotherapy in a Rare Case of Intraductal Apocrine Carcinoma of Parotid Gland.

Introduction Apocrine carcinoma, a cancer of sweat glands, is very rare, with a global incidence of 0.0049 to 0.0173 cases per 100,000 persons annually. It is usually found in axilla and anogenital areas. The intraductal apocrine variety of salivary duct carcinoma in the parotid gland is very rare and aggressive and may be due to ectopic sweat glands in the parotid gland duct or metaplastic change of the salivary duct epithelium. It usually presents in an advanced stage. Even though surgery is the standard of care in most head and neck cancers, there are no standard guidelines for the treatment of intraductal apocrine parotid carcinoma, which is different from other head and neck cancers due to its rare incidence, aggressive behavior, and poor prognosis. Case presentation We present a rare case of intraductal apocrine salivary duct carcinoma of the left parotid gland, presented in a locally advanced stage with very high chances of recurrence after surgery, and discuss the role of volumetric modulated arc technique radiotherapy in its management. Conclusion Intraductal apocrine salivary duct carcinoma usually has androgen receptor expression, and lack of expression is associated poor prognosis. Even with complete resection, it has a high recurrence rate. Volumetric modulated arc technique radiotherapy (VMAT) decreases recurrence and increases survival by irradiating the areas more likely of recurrence, with minimal toxicity to surrounding normal tissues.