Mammary-type Metaplastic Carcinoma Arising From Vulvar Hidradenoma Papilliferum: A Case Report.
Chandni Desai, Peng Wang, Melissa Tjota et al.
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Case in brief
A patient presented with a labial mass. Histology showed vulvar hidradenoma papilliferum with focal ductal carcinoma in situ, adjacent to a biphasic malignant tumor comprising high-grade carcinoma and infiltrating sarcomatoid components with pleomorphic cells. Immunohistochemistry supported mammary-type differentiation, and both invasive components showed aberrant cytoplasmic p53 expression. Molecular analysis identified pathogenic mutations in TP53, PIK3CA, APC, and NF1. The findings were interpreted as mammary-type metaplastic carcinoma likely arising from hidradenoma papilliferum.
What made this case unusual
The tumor combined hidradenoma papilliferum and focal ductal carcinoma in situ with adjacent biphasic metaplastic carcinoma, including a pleomorphic sarcomatoid component—an exceedingly rare malignant transformation in this setting.
Diagnostic / clinical pearl
In a vulvar lesion with hidradenoma papilliferum, an adjacent biphasic malignancy with carcinomatous and sarcomatoid components may represent mammary-type metaplastic carcinoma; morphology and immunohistochemistry can support this interpretation.
Why it matters
The case broadens the described morphologic, immunohistochemical, and molecular spectrum of mammary-type malignancies arising in the vulvovaginal region.