Invasive Fibromatosis in the Parotid Region of Infants: One Case Report

本文报道一例9月龄女婴右侧腮腺区侵袭性纤维瘤病的罕见病例。患儿以右耳后无痛性包块就诊，影像学检查显示：CT平扫呈等密度，增强后显著强化；MRI示T1WI等信号伴斑片低信号，T2WI高信号伴胶原纤维低信号区，DWI高信号但ADC值正常，增强扫描呈现特征性“反转强化”(细胞富集区显著强化)。术后病理证实梭形细胞束状排列伴胶原增生，免疫组化Vimentin (+)、Ki-67 (15%)。讨论指出AF在腮腺区发病率不足2%，MRI通过T2WI信号分层(高信号区对应细胞增殖，低信号区提示胶原沉积)、动态增强“快进慢出”曲线及DWI-T2透过效应，可有效鉴别纤维肉瘤、孤立性纤维瘤等病变。This article reports a rare case of aggressive fibromatosis in the right parotid gland region of a 9-month-old female infant. The patient presented with a painless mass behind the right ear. Imaging examinations showed that the CT scan revealed isodensity with significant enhancement after contrast; MRI indicated isosignal on T1-weighted images with patchy low signal, high signal on T2-weighted images with areas of low signal corresponding to collagen fibers, high signal on diffusion-weighted imaging (DWI) but normal apparent diffusion coefficient (ADC) values, and characteristic “reverse enhancement” on enhanced scans (significant enhancement in cellularity-rich areas). Postoperative pathology confirmed a fascicular arrangement of spindle cells with collagen proliferation, and immunohistochemistry showed Vimentin positive and Ki-67 at 15%. The discussion pointed out that the incidence of aggressive fibromatosis in the parotid region is less than 2%. MRI can effectively differentiate between fibrosarcoma, solitary fibromas, and other lesions through T2-weighted signal stratification (high signal areas correspond to cellular proliferation, and low signal areas suggest collagen deposition), dynamic contrast enhancement “fast in, slow out” curves, and DWI-T2 through-transmission effects.