Abstract

A 70-year-old Caucasian male presented with a slowly enlarging lesion on the right medial brow for over a year. He became concerned when it developed a dark purple color but was otherwise asymptomatic. Physical exam noted a ~1 cm, soft and mobile, deep purple nodule. Given the clinical appearance and concern for a vascular growth, a soft tissue ultrasound was performed revealing a superficial complex cystic lesion without internal blood flow. The lesion was excised and histopathologic examination showed a multiloculated cyst with an eosinophilic lining composed of pseudostratified columnar epithelial cells with apical snouting and decapitate secretion. Adjacent to the dermal cystic proliferation there were numerous pigment-laden macrophages containing finely granulated melanin (confirmed by melanin staining, iron stain was negative). The diagnosis of a pigmented apocrine hidrocystoma was made. Apocrine hidrocystomas, also known as apocrine cystadenomas, are benign neoplasms of the sweat duct epithelium that commonly present as solitary, translucent to bluish papules on the head and neck with a predilection for the eyelids. These growths are almost exclusively seen in adults and clinically mimic basal cell carcinoma, melanocytic or vascular neoplasms. When clinical diagnosis is uncertain, ultrasound can be implemented to assess for vascular supply or connection to underlying structures. Malignant transformation to apocrine adenocarcinoma is exceedingly rare. The characteristic bluish hew seen in apocrine hidrocystomas has been attributed to the Tyndall effect – scattering of shorter wavelengths of light in a colloidal system. The clinically apparent pigmentation of these neoplasms has been associated in the literature with intracytoplasmic lipofuscin deposits, finely pigmented melanin granules, or deposits of hemosiderin. We present this rare case of a large pigmented apocrine hidrocystoma of the brow with numerous melanophages mimicking a vascular growth.

Financial Disclosure:
No current or relevant financial relationships exist.