P143 Shining a light on a rare cancer: bridging data gaps for better care

Abstract Microcystic adnexal carcinoma (MAC) is a rare and aggressive sweat gland tumour. It poses diagnostic and treatment challenges due to its subtle presentation, histological similarity with other adnexal tumours, and high risk of perineural invasion. Epidemiological data on MAC are limited. This study provides an overview of national data from the National Cancer Registry of Ireland (NCRI) and insights from a tertiary skin cancer referral centre regarding MAC in Ireland. The NCRI recorded 17 cases of MAC from 2007 to 2021, comprising 8 men and 9 women aged 43–84 years (mean age 62 years). Most tumours (15) were located on unspecified parts of the face, with two cases on the lip and ear. At an Irish tertiary skin cancer centre, a review of cases of MAC from 2007 to 2021 identified four confirmed cases, involving two men and two women aged 59–83 years. Tumour locations included the cheek, upper lip, nose and breast – the latter not captured by NCRI data. All patients underwent Mohs micrographic surgery (MMS). One patient had extensive perineural invasion, and two had muscle invasion, one of whom had a recurrence 4 years after MMS requiring wide local excision and adjuvant radiotherapy. This study reveals discrepancies between national cancer registry data and tertiary centre findings, suggesting gaps in cancer reporting for rare tumours like MAC. The limited number of cases treated at one of two MMS centres in Ireland over 14 years raises concerns about access to specialized care. Addressing reporting gaps, increasing clinician awareness, and expanding access to MMS are essential for improving patient outcomes and guiding public health strategies for rare malignancies.