Ultrasonographic and pathologic findings of recurred clear cell hydradenoma

Abstract

Clear cell hidradenoma is a rare benign sweet gland origin tumor in the skin and subcutaneous fat. Almost cases were benign and well removed without recurrence. Therefore, the ultrasonographic (US) study was not performed in most cases. We experienced a case of recurred clear cell hidradenoma and presented here US and pathologic findings of this case. We also discussed clear cell hidradenoma and hidradenocarcinoma. A Case report: A 48-year old woman presented with a solitary nodule on the left upper arm. Two years ago, the patient visited a hospital and got excision without a specific problem. One year later, the nodule recurred. The lesion gradually grew again. A bloody discharge occurred. The patient visited our hospital for further evaluation and removal of the mass. The US showed an about 2-cm sized, ovoid, well circumscribed solid and cystic nodule at the subcutaneous fat layer. Increased vascularity was found on solid portion and the peripheral area. Malignant mass was suspected on the basis of clinical history and US finding. Excisional biopsy was done. On pathology, there was basaloid cell proliferation adjacent to the cyst. Clear cell changes with multiple sweet ducts were also found. These findings are compatible with sweet gland origin tumor. Mitotic activity was up to 2 mitoses/10 high-power fields. Discussion: Clear cell hidradenoma is usually a single, slow-growing, round, mobile, cutaneous nodule ranging between 0.5 cm and 3.0 cm in diameter. Cho, et al, suggested that US findings of benign clear cell hidradenoma were well-defined cystic masses with mural nodules or well-defined solid tumors with hypoechogenicity. Hypervascularity was usually combined. Recently Nazarian et al, described that infiltrative growth pattern, deep extension, necrosis, nuclear pleomorphism, and ≥ 4 mitoses per 10 high-power fields are specific histologic features of clear cell hidradenocarcinoma. Repeated local recurrences and/or systemic metastasis was often documented in the cases of clear cell hidradenocarcinoma. When the US shows a recurred cystic mass with solid mural nodules and increased vascularity, clear cell hidradenoma or hidradenocarcinoma should be included in the differential diagnosis.