[Clinicopathological features of ectopic meningothelial hamartoma]

Objective: To investigate the clinicopathological features, diagnosis and differential diagnosis of ectopic meningothelial hamartoma (EMH). Methods: Three cases of EMH diagnosed in the First Affiliated Hospital of Nanjing Medical University from January 2014 to December 2020 were enrolled. All cases were evaluated by clinical and imaging features, HE and immunohistochemical staining, and the relevant literature was reviewed. Results: There were one male and two female patients, aged 2, 67 and 19 years, respectively. Clinically, they presented as skin masses in the head and face region (two cases) and sacro-coccygeal region (one case). Grossly, the lesions ranged in size from 1.6 cm to 8.9 cm. Microscopically, the lesions were ill-defined, and located in the dermis and subcutis, and showed pseudovascular channels lined by monolayer of cuboidal to flattened epithelium with mild atypia, with variable cystic cavity formation. There was prominent interstitial fibrosis. Concentric, lamellated, onion skin-like arrangement with short spindle or ovoid cells and psammoma bodies were noted. Immunohistochemically, these cells were strongly positive for SSTR2, EMA, vimentin and progesterone receptor. Ki-67 positive index was low, approximately 1%. Conclusions: EMH is uncommon. Definitive diagnosis relies on histopathologic examination. The importance in recognizing the lesions is to differentiate from other more aggressive tumors.