Extensive Squamous Metaplasia in Hidradenoma Papilliferum of Vulva: Illusion of Squamous Cell Carcinoma

BackgroundHidradenoma papilliferum is a rare, slow-growing, benign, cystic, papillary tumour occurring in middle-aged females, in the anogenital region commonly. It involves the anogenital mammary-like glands and is usually asymptomatic. Simple excision is curative.Case ReportWe present a case of hidradenoma papilliferum of long-standing duration with extensive squamous metaplasia. A post-menopausal lady presented with an exophytic growth on the left labia majora and part of mons pubis. It was initially misdiagnosed on the basis of vulvar biopsy and managed as squamous cell carcinoma of the vulva. The final histopathology revealed an epithelial tumour involving the vulva with extensive squamous metaplasia. The tumour involved mainly the dermis and the subcutaneous tissue. This is the first case in the literature where the diagnosis of hidradenoma papilliferum was confused with squamous cell carcinoma of the vulva due to its clinical presentation and extensive squamous metaplasia.ConclusionDiagnosis of hidradenoma papilliferum should be kept in mind if a woman presents with vulval papillary or nodular lesions. An expert clinical and histopathological review should be done to avoid misdiagnosis.