A brief report of a rare case of giant apocrine hidrocystoma presenting as a scalp hematoma

Introduction

Apocrine hidrocystoma is a benign cystic tumour. Apocrine hidrocystomas commonly occur as solitary cystic lesions that arise from the adenomatous cystic proliferation of apocrine glands. Though the head and neck region is the site of predilection, occurrence in the scalp is extremely rare. We report a rare case of giant apocrine hidrocystoma with an unusual presentation as scalp hematoma.

Case report

Clinical findings

We report a 60-year-old male who presented with a non-tender red brown scalp nodule of acute onset.

The patient first noticed it a couple of weeks ago. During this time the lesion showed a progressive course. Upon physical examination, the lesion measured 2.8 × 2.0 cm – and was mobile and non-tender. The patient had no significant medical history. The lesion was managed by surgical excision with the clinical assumption that it represented a hematoma.

Pathological findings

The excised skin ellipse measured 3.2 × 2.2 × 2 cm and contained a cyst measuring 2.8 cm in maximum dimension with a thin wall measuring 0.1 cm. The cyst contained minimal clear fluid and its wall was devoid of firm nodules and hemorrhage. Microscopic examination revealed a unilocular dermal cystic lesion lined by a double layer of epithelium (Fig. 1). The inner layer contained large columnar cells with eosinophilic cytoplasm which had luminal decapitation secretion, denoting apocrine differentiation (Fig. 2). The outer layer was flat and composed of myoepithelial cells. Based on these findings, the lesion was diagnosed as apocrine hidrocystoma of the scalp.

Discussion

Apocrine hidrocystomas or cystadenomas are benign cystic tumours of the secretory portion of apocrine sweat glands, first described by Mehregan in 1964 [1]. Apocrine hidrocystomas commonly occur as solitary cystic lesions that arise from the adenomatous cystic proliferation of apocrine glands [2-4]. Though the head and neck region is the site of predilection, occurrence in the scalp is extremely rare, with two cases reported in the English and French literatures [2, 4]. Hidrocystoma may show eccrine or apocrine differentiation. The presence of a decapitation secretion differentiates apocrine hidrocystomas from eccrine hidrocystomas [5].

The current case is unusual presentation as a hematoma in the scalp. Differential diagnoses considered at the time included hemangioma, lipoma, epidermal inclusion cyst, and subcutaneous dermoid cyst. However, the histological findings are pathognomonic of apocrine hidrocystoma.

Apocrine cystadenoma should be considered in the differential diagnosis of large cystic subcutaneous masses of the scalp.

References

 1. Mehregan AH. Apocrine cystadenoma, a clinicopatholoical study with special reference to the pigmented variety. Arch Dermatol 1964; 90: 274-279.  

2. Matsushita S, Higashi Y, Uchimiya H, et al. Case of giant eccrine hidrocystoma of the scalp. J Dermatol 2007; 34: 586-587.  

3. Giuffrida TJ, Schoenfeld D, McCall CO. Gradually Enlarging Bilateral Facial Nodules Arch Dermatol 2001; 137: 657-662.  

4. Vittori F, Colomb D. Complex sweat gland tumor of the scalp. Association of a papillous syringocystadenoma and an apocrine hidrocystoma. Arch Anat Cytol Pathol 1976; 24: 51-55.  

5. Alfadley A, Al Aboud K, Tulba A, Mourad MM. Multiple eccrine hidrocystomas of the face. Int J Dermatol 2001; 40: 125-129.

Address for correspondence

Dina El Demellawy MB BCh, MD, MS, PhD, FRCPC

Assistant Professor, Northern Ontario Medical School

Staff Pathologist, William Osler Health Centre

Department of Pathology and Laboratory Medicine,

2100 Bovaird Drive East, Brampton

Ontario, Canada

tel. 416-747-3400 ext. 57812

e-mail: dina.demellawy@sympatico.ca