Intestinal Type Adenocarcinoma from Inverted Papilloma: A Rare Recurrence

Inverted Papilloma (IP) is an uncommon and locally aggressive benign tumour of sinonasal region, which tends to recur after surgical resection. Most tumours are confined to the lateral nasal wall and sinuses, with maxillary sinus being most commonly affected and a male preponderance. It has a known association with in situ and invasive carcinomas with a <10% rate of malignant transformation. Most common association has been seen with squamous cell carcinoma and extremely rare association with adenocarcinoma and small cell carcinoma. A 36-year-old male presented with a left sided polypoidal nasal mass and underwent a polypectomy. Pathology results showed IP with mild dysplasia. The polypoidal growth reappeared on the same side after a period of 10 months and on histopathological examination, the growth revealed features of intestinal type adenocarcinoma. IP recurring as adenocarcinoma is rare and even after exhaustive literature search only few cases could be found. Two studies have described recurrence of adenocarcinoma in existing IP previously. We report an unusual case of inverted papilloma showing malignant transformation into an intestinal type adenocarcinoma in a 36-year-old male patient within 10 months of previous surgery.