Giant clear cell hidradenoma of the knee

Clear Cell Hidradenoma: Characteristic Imaging Features on Ultrasonography, Computed Tomography, and Magnetic Resonance Imaging

OBJECTIVES

The purpose of this study was to evaluate the imaging features of clear cell hidradenoma on ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI).

METHODS

The radiologic and pathologic databases at 2 medical institutions were searched retrospectively from 2004 to 2016 to identify patients with a diagnosis of clear cell hidradenoma. Ultrasonographic, CT, and MRI features were described, and pathologic specimens were reviewed.

RESULTS

There were 5 female and 4 male patients. The mean patient age was 48.9 years (range, 28-70 years). Five patients underwent only US; 2 patients underwent only CT; 1 patient underwent both US and CT; and 1 patient underwent US and MRI. Most of the tumors were located primarily in the subcutaneous fat layer. The mean tumor size was 18.4 mm. On US, 6 masses had a heterogeneous echo texture, including an anechoic portion with protruding echogenic portions. Two masses had multiple septa in the anechoic portion. On color Doppler US, blood flow was both central and peripheral in 5 patients. All 3 cases seen on CT presented as a low-attenuation mass with an enhanced solid internal nodule. On MRI, the mass showed heterogeneous signal intensity on T2-weighted images and enhancement of the peripheral wall and internal solid component on contrast-enhanced T1-weighted images.

CONCLUSIONS

Clear cell hidradenoma is usually located in the subcutaneous fat layer, has a well-defined margin, appears as a cystic mass with an internal solid nodule, and occasionally has multiple septa on US, CT, and MRI.

A giant benign clear cell hidradenoma on the anterior trunk

Clear cell hidradenoma (CCH) is an uncommon variant of benign cutaneous adnexal tumors. These tumors are clinically asymptomatic, solitary dermal nodules. They occur most frequently on the scalp, face abdomen and extremities. Growth is slow and malignant change is rare. 45-year-old woman presented with a nodule which had begun 4 years ago as a small nodular asymptomatic lesion and had a central ulceration and a minimal hemorrhagic discharge on her anterior abdomen wall. On dermatologic examination there was a 6.5×5×4 cm non-tender, soft reddish purple nodule, with lobular appearance and ulceration. In the laboratory investigations, all hematologic and biochemical tests were normal. A computed tomography (CT) scan demonstrated a cystic tumor with lobulated contour with contrast enhancement. The lesion was excised totally. In histopathological examination, the tumor was composed of biphasic smaller dark polygonal cells and larger clear cells and coarse nuclear chromatine. There were duct like structures. Immunohistochemical investigation was done for the suspicion of malignancy. Cytoplasm of clear cells and of duct like structures showed PAS-positive and d-PAS resistant staining. There was a positive reaction to epithelial membrane antigen and carcinoembryonic antigen. The mitotic index in Ki 67 examination was low. All these findings confirmed the diagnosis of benign CCH.