Salisbury Taylor, Rendi Mara, Bhalli Rabia, Bean Gregory R, Allison Kimberly H, Troxell Megan L
Stanford University Medical Center Pathology, Stanford, CA, USA.
Hospital Pathology Associates, Minneapolis, MN, USA.
Histopathology. 2025 Aug;87(2):246-257. doi: 10.1111/his.15459. Epub 2025 May 4.
Ductal carcinoma in-situ (DCIS)-like invasive carcinoma of the breast is an underdiagnosed pattern of invasive carcinoma that is challenging to separate from DCIS. We have observed some cases of DCIS-like invasive carcinoma in which smooth muscle myosin heavy chain (SMMHC) or calponin are strongly expressed in vessels tightly encircling the periphery of the tumour nodules, closely mimicking myoepithelium and potentially leading to misinterpretation as in-situ disease. We aimed to assemble and characterise a series of DCIS-like invasive carcinoma, with particular attention to presence and immunostaining of encircling vessels.
We collected 23 cases of DCIS-like invasive carcinoma and performed SMMHC, calponin, p63, CK5/6, SMA, CD31 and D2-40 immunohistochemistry. All the cases showed no true myoepithelial cell staining, supporting invasive disease. Eighteen of the cases displayed vessels tightly encircling at least 25% of the tumour, which we termed tumour-associated microvasculature (TAM). Of the TAM cases, 11 had at least some SMMHC vascular expression (termed tumour-associated microvasculature mimicking myoepithelium, TAMMM). The vascular SMMHC was strong, circumferential and closely mimicked myoepithelial staining in three of the TAMMM cases. Eleven cases had focal/patchy, often weaker, calponin staining in the vessels. CD31 was universally positive in TAMMM, supporting that the observed SMMHC or calponin expression encircling the tumour nodules was due to vascular staining. D2-40 was negative in all cases, confirming the lack of lymphatic endothelium.
Our findings illustrate TAMMM as a rare but important pitfall of myoepithelial cell immunohistochemistry in the distinction of DCIS-like invasive carcinoma from in-situ disease and support a panel approach to myoepithelial immunohistochemistry.
乳腺导管原位癌（DCIS）样浸润性癌是一种诊断不足的浸润性癌模式，难以与DCIS区分开来。我们观察到一些DCIS样浸润性癌病例，其中平滑肌肌球蛋白重链（SMMHC）或钙调蛋白在紧密环绕肿瘤结节周边的血管中强烈表达，酷似肌上皮，可能导致误诊为原位疾病。我们旨在收集并描述一系列DCIS样浸润性癌病例，特别关注环绕血管的存在情况及免疫染色。
我们收集了23例DCIS样浸润性癌病例，并进行了SMMHC、钙调蛋白、p63、CK5/6、平滑肌肌动蛋白（SMA）、CD31和D2-40免疫组化检测。所有病例均未显示真正的肌上皮细胞染色，支持浸润性疾病的诊断。其中18例病例显示血管紧密环绕至少25%的肿瘤，我们将其称为肿瘤相关微血管（TAM）。在TAM病例中，11例至少有一些SMMHC血管表达（称为肿瘤相关微血管模拟肌上皮，TAMMM）。在3例TAMMM病例中，血管SMMHC呈强阳性、环绕性，且酷似肌上皮染色。11例病例血管中有局灶性/斑片状、通常较弱的钙调蛋白染色。CD31在TAMMM中普遍呈阳性，支持观察到肿瘤结节周围的SMMHC或钙调蛋白表达是由于血管染色所致。所有病例D2-40均为阴性，证实不存在淋巴管内皮。
我们的研究结果表明，TAMMM是DCIS样浸润性癌与原位疾病鉴别中肌上皮细胞免疫组化罕见但重要的陷阱，并支持采用联合免疫组化方法进行肌上皮检测。
