Department of Surgical Pathology, Tata Memorial Hospital, Homi Bhabha National Institute (HBNI) University, Parel, Maharashtra, Mumbai, India.
Pathologica. 2021 Dec;113(6):456-462. doi: 10.32074/1591-951X-250.
The clinicopathological spectrum of INI1 deficient tumors is expanding. Epithelioid sarcoma (ES) is a rare sarcoma of uncertain differentiation, more often occurring in the extremities and uncommonly in the deep soft tissues. Histopathologically, it manifests in the form of classical, proximal, or hybrid types, the latter two characterized by rhabdoid cytomorphology. Immunohistochemically, ESs display loss of INI1/SMARCB1 and genetically associated with high percentage of deletions. We report an extremely uncommon case of a retroperitoneal tumor in a 42-year-old male, who presented with abdominal discomfort. Radiologic imaging disclosed a 12 cm-sized retroperitoneal mass without involvement of any organ parenchyma. The patient underwent tumor excision with left-sided nephrectomy at another hospital. A review of the paraffin-embedded tissue sections revealed a multinodular tumor, composed of dyscohesive epithelioid tumor cells and focally arranged in cords, containing moderate to abundant, eosinophilic cytoplasm, vesicular nuclei, containing prominent nucleoli, including cells with rhabdoid cytomorphology, in a conspicuous myxoid stroma. A focal tumor area resembled proximal-type of ES. Immunohistochemically, tumor cells displayed positivity for pan cytokeratin (AE1/AE3), epithelial membrane antigen (EMA), vimentin and focally for CA125, while these were negative for CD34, S100 protein, CKIT, DOG1, and INI1/SMARCB1. To the best of our knowledge, this constitutes the first case of a malignant tumor with epithelioid morphology, displaying myxoid matrix and loss of INI1/SMARCB1, resembling a myxoid variant of an epithelioid sarcoma and myoepithelioma-like tumor of the vulvar tumor, occurring in the retroperitoneum. A review of similar cases, differential diagnosis and treatment-associated implications are presented.
INI1 缺陷肿瘤的临床病理谱正在扩大。上皮样肉瘤（ES）是一种罕见的分化不确定的肉瘤，更多见于四肢，深部软组织罕见。组织病理学上，它表现为经典型、近端型或混合型，后两者的特征是横纹肌样细胞形态。免疫组化显示 ES 缺失 INI1/SMARCB1，与高比例缺失相关。我们报告了一例非常罕见的腹膜后肿瘤病例，患者为 42 岁男性，表现为腹部不适。影像学检查显示腹膜后 12cm 大小肿块，无任何器官实质受累。患者在另一家医院接受肿瘤切除和左侧肾切除术。对石蜡包埋组织切片进行复习，发现一个多结节性肿瘤，由黏附性差的上皮样肿瘤细胞组成，局灶性排列成条索状，含有中等至丰富的嗜酸性细胞质、泡状核，含有明显的核仁，包括具有横纹肌样细胞形态的细胞，在明显的黏液样基质中。一个局灶性肿瘤区域类似于近端型 ES。免疫组化显示，肿瘤细胞对广谱细胞角蛋白（AE1/AE3）、上皮膜抗原（EMA）、波形蛋白呈阳性，局灶性对 CA125 呈阳性，而对 CD34、S100 蛋白、CKIT、DOG1 和 INI1/SMARCB1 呈阴性。据我们所知，这是首例具有上皮样形态、黏液样基质和 INI1/SMARCB1 缺失的恶性肿瘤，类似于黏液样变异型上皮样肉瘤和外阴肿瘤的肌上皮样肿瘤，发生在腹膜后。回顾了类似病例，提出了鉴别诊断和治疗相关的意义。
