Gilbert Aubre, Wieland Rebekah, Zacher Natasha, Rieger Kerri, Berry Gerald J, Novoa Roberto
Department of Pathology, Stanford University School of Medicine, Stanford, CA.
Am J Dermatopathol. 2025 Jan 1;47(1):e6-e11. doi: 10.1097/DAD.0000000000002848. Epub 2024 Oct 31.
Mesothelioma of the tunica vaginalis testis (MMTVT) is a rare neoplasm comprising <3% of all cases of malignant mesothelioma (MM). MMTVT derives from the tunica vaginalis testis, an outpouching of the mesothelial-lined abdominal peritoneum that detaches from the abdominal cavity after the descent of the testis. Similar to pleural mesothelioma, asbestos exposure is a known risk factor. However, MMTVT has a better prognosis than pleural mesothelioma. Cutaneous metastases from MMTVT are exceedingly rare. Herein, we describe a case of a 67-year-old man with a history of asbestos exposure presenting with scrotal pain and indurated plaques on his lower abdomen and scrotum. Histologic sections showed a sheet-like dermal proliferation comprising epithelioid cells with necrosis and increased mitotic activity. The clinical and histologic differential diagnosis was broad, including metastatic carcinoma, melanoma, sarcoma, germ cell tumor, hematologic malignancy, neuroendocrine carcinoma, and malignant mesothelioma. By immunohistochemistry, the neoplastic cells were positive for WT1, D2-40, and AE1/AE3, with rare positivity for calretinin, consistent with a diagnosis of mesothelioma. Additional immunohistochemical studies provided no support for the other diagnostic considerations listed above. BAP1 showed retained nuclear expression (normal) by immunohistochemistry. A DNA sequencing panel identified copy number losses in CDKN2A, MTAP, CDKN2B, and NF2, which are frequently identified genetic alterations in malignant mesothelioma. Subsequent testicular imaging demonstrated a diffusely thickened scrotal wall with an enlarged left testicle. Overall, this represents a case of malignant mesothelioma presenting with cutaneous metastases to the scrotum and lower abdomen, with clinical and imaging features suggestive of primary MMTVT. The International Mesothelioma Interest Group recommends using at least 2 mesothelial markers, such as calretinin, WT1, CK5/6 or D2-40, and 2 epithelial markers, such as claudin-4, CEA, MOC-31, as well as a broad-spectrum cytokeratin stain (AE1/AE3) as part of an initial immunohistochemical panel. Metastatic mesothelioma should be included in the differential diagnosis of malignant epithelioid dermal tumors with unusual staining patterns.
睾丸鞘膜间皮瘤（MMTVT）是一种罕见肿瘤，在所有恶性间皮瘤（MM）病例中占比不到3%。MMTVT起源于睾丸鞘膜，它是间皮衬里的腹膜的一个突出部分，在睾丸下降后与腹腔分离。与胸膜间皮瘤相似，石棉暴露是已知的危险因素。然而，MMTVT的预后比胸膜间皮瘤要好。MMTVT的皮肤转移极为罕见。在此，我们描述一例67岁男性病例，有石棉暴露史，表现为阴囊疼痛以及下腹部和阴囊出现硬结性斑块。组织学切片显示为片状真皮增生，由伴有坏死和有丝分裂活性增加的上皮样细胞组成。临床和组织学鉴别诊断范围广泛，包括转移性癌、黑色素瘤、肉瘤、生殖细胞肿瘤、血液系统恶性肿瘤、神经内分泌癌和恶性间皮瘤。通过免疫组化，肿瘤细胞WT1、D2 - 40和AE1/AE3呈阳性，钙视网膜蛋白呈罕见阳性，符合间皮瘤诊断。其他免疫组化研究不支持上述其他诊断考虑。BAP1免疫组化显示核表达保留（正常）。DNA测序 panel 鉴定出CDKN2A、MTAP、CDKN2B和NF2存在拷贝数缺失，这些是恶性间皮瘤中常见的基因改变。随后的睾丸成像显示阴囊壁弥漫性增厚，左侧睾丸增大。总体而言，这是一例恶性间皮瘤伴有阴囊和下腹部皮肤转移的病例，其临床和影像学特征提示原发性MMTVT。国际间皮瘤兴趣小组建议使用至少2种间皮标志物，如钙视网膜蛋白、WT1、CK5/6或D2 - 40，以及2种上皮标志物，如claudin - 4、CEA、MOC - 31，还有广谱细胞角蛋白染色（AE1/AE3）作为初始免疫组化 panel 的一部分。转移性间皮瘤应纳入具有异常染色模式的恶性上皮样皮肤肿瘤的鉴别诊断。
