Primary Cutaneous Mucinous Adenocarcinoma of Facial Region Treated with Multimodality Therapy: Case Series of Rare Malignancy

Primary mucinous carcinoma (PMC) of the skin is a rare malignancy with an indolent course. It is a locally aggressive tumor.  The most common location is the face and scalp. The primary modality of treatment is surgery, while radiation may be reserved as an adjuvant for high-risk factors or as definitive when a patient refuses surgical intervention. The use of adjuvant and definitive radiotherapy has very limited reporting in the literature. We have reported 4 cases of primary mucinous carcinoma of the skin treated with adjuvant or definitive radiotherapy. All were located in the face and scalp region. All 4 cases had a very indolent course. 3 were treated with adjuvant and 1 with definitive radiotherapy, with two patients being treated with surface mould brachytherapy. Indications of adjuvant radiotherapy were positive, close, or unknown resection margin status. A radiation dose of 42 Gy to 60 Gy was used; the maximum dose per fraction was 4 Gy. At the end of the follow-up period, all patients had loco regionally controlled disease. Both acute and late skin toxicity profiles were favourable, with one patient having acute grade III skin toxicity. Radiation therapy may be safely used as an adjuvant or definitive treatment of primary mucinous carcinoma of the skin; however, more prospective data is needed to have consensus guidelines.