Department of Pathology and Laboratory Medicine and The Arnie Charbonneau Cancer Centre, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
Department of Dermatology, University of Heidelberg, Heidelberg, Germany.
Histopathology. 2020 Sep;77(3):449-452. doi: 10.1111/his.14130. Epub 2020 Jul 2.
Microcystic adnexal carcinoma is a distinctive sweat duct carcinoma of low-grade malignant potential with a risk for locally destructive growth and local recurrence. Distant metastases and disease-related mortality are exceptional. The histological hallmarks of these tumours are the diffusely infiltrative growth within the dermis, the frequent invasion of subcutaneous structures, the presence of perineurial invasion, and the bland cytological features. The tumours are organised in cords and strands, and show keratocyst formation and duct differentiation in varying proportions. Marked cytological atypia, nuclear pleomorphism, brisk and atypical mitotic activity and necrosis are not typically seen in these tumours.
We report two patients presenting with large, slowly growing tumours on the face showing areas of morphologically high-grade carcinoma arising on a background of unequivocal microcystic adnexal carcinoma. Both patients are alive with follow-up of up to 6 years, with no evidence of disease.
Morphologically high-grade transformation in microcytic adnexal carcinoma is a rare phenomenon that does not appear to confer a risk for aggressive behaviour. Recognition depends on sampling of the areas of conventional microcystic adnexal carcinoma.
微囊性附属器癌是一种具有低度恶性潜能的独特汗腺癌，具有局部破坏性生长和局部复发的风险。远处转移和与疾病相关的死亡率是罕见的。这些肿瘤的组织学特征是真皮内弥漫性浸润性生长、频繁侵犯皮下结构、存在神经周围浸润以及温和的细胞学特征。肿瘤呈条索状排列，表现为不同比例的角化囊肿形成和导管分化。这些肿瘤通常不具有明显的细胞学异型性、核多形性、活跃和非典型有丝分裂活动以及坏死。
我们报告了两名患者，他们面部出现了大的、生长缓慢的肿瘤，在明确的微囊性附属器癌背景上出现了形态上高级别癌的区域。两名患者均存活且随访时间长达 6 年，无疾病证据。
微囊性附属器癌中形态上的高级别转化是一种罕见现象，似乎不会增加侵袭性行为的风险。识别依赖于对常规微囊性附属器癌区域的取样。
