An unusual ischiorectal fossa mass()

INTRODUCTION: Peri-anal fistulae commonly present with collections requiring surgical intervention. The most common cause of a peri-anal mass is abscess formation secondary to anal gland sepsis. In certain patient groups such as those over 65 or with atypical presenting symptoms there are other important considerations. PRESENTATION OF CASE: A 70-year old male was referred by his general practitioner with symptoms of obstructed defaecation and a palpable mass in the ischiorectal fossa. He had previously undergone three operations for complex peri-anal fistulae in another hospital. Due to the previous history of surgery, seroma formation was considered and computed tomography guided drainage of the lesion was performed unsuccessfully. Given symptoms of obstructed defecation and need for histological diagnosis excision was undertaken. The approach was through a right pararectal incision over the bulk of the mass. Skin and pararectal tissue were divided revealing a mucinous lesion with multiple lobules adherent to pararectal tissue. Following histopathological examination a diagnosis of low grade mucinous neoplasm was made. DISCUSSION: Primary mucinous neoplasm in the ischiorectal fossa is very rare. Diagnostic criteria for adenocarcinoma arising from perianal fistulae have previously been established by Rosser et al. but this lesion does not fall into this category. It is categorised as a mucinous cystic neoplasm of uncertain malignant potential. The differential diagnoses are discussed. CONCLUSION: Consideration should be given to a range of pathologies in cases of atypical peri-anal masses.