Sir, Hidrocystomas are rare benign cystic tumors of epidermal appendages (estimated incidence of one per thousand of submitted cutaneous biopsies) and traditionally classified into apocrine and eccrine types based on their classical histopathology and histogenesis.[12] In 1964, Mehregan first described apocrine hidrocystoma (apocrine cystadenoma) as a benign cystic adenomatous proliferation of the secretory coil of apocrine glands.[134] Postulated pathogenesis of apocrine hidrocystoma implies retention of sweat and subsequent dilation of sweat duct apparatus due to occlusion or blockage. Clinically, they appear as a solitary, cystic, well-circumscribed, dome-shaped reddish or blackish brown, nontender, skin-colored lesion measuring 3–15 mm usually between 30 and 70 years of age. Their most common site of predilection is head-and-neck region and their occurrence in the scalp is rarely reported.[15] Although usually appearing as solitary lesions, multiple apocrine hidrocystomas have rarely been described in association with Gorlin-Goltz and Schopf–Schulz–Passarge syndromes.[12] Excision biopsy and histopathology are essential for confirmation of the diagnosis. Herein, we report a rare case of recurrent apocrine hidrocystoma occurring on the scalp, an unusual site.[356] A 42-year-old female presented with a reddish-brown, nontender, well-circumscribed, gradually progressive mobile cystic swelling on the scalp measuring 3.0 cm × 2.5 cm for 6 months' duration. She gave a history of a similar lesion on the scalp about 5 years back which after surgical resection and histopathological examination was diagnosed to be apocrine hidrocystoma. No history of trauma or any other significant medical history was observed. Based on history and symptoms, a clinical diagnosis of the recurrent apocrine hidrocystoma was made and the lesion was surgically excised with clear margins which sent for histopathological examination. Macroscopic examination of skin ellipse measured 2.5 cm × 2.2 cm × 1.8 cm and contained a cyst measuring 1.6 cm in maximum dimension with a thin wall. The cyst contained minimal clear fluid and its wall was devoid of any firm nodules or papillary excrescences. Microscopic examination of hematoxylin and eosin-stained slides revealed a multilocular bilayered dermal cyst lined by an inner layer of cuboidal and tall columnar secretory cells of variable heights showing eosinophilic cytoplasm with luminal decapitation secretion, suggesting apocrine differentiation and surrounded by a peripheral layer of elongated myoepithelial cells [Figures 1 and 2]. There was no evidence of squamous or mucous metaplasia seen. There was no inflammation or cytological atypia seen. Based on characteristic histolopathogical features, a diagnosis of recurrent apocrine hidrocystoma of the scalp was made. The patient was kept on follow-up and has not reported any recurrence so far for the past 1 year.Figure 1: Multilocualted cystic lesion in the scalp showing various sized cysts (H and E stain, ×100)Figure 2: Cyst wall lined by double-layered epithelium showing the inner layer of apocrine-like secretory epithelium showing eosinophilic cytoplasm with apocrine snouts and fringes and outer layer of elongated myoepithelial cells (H and E stain, ×200)Due to their typical clinical appearance and anatomical site location, apocrine hidrocystoma must be differentiated from other similar benign lesions, such as eccrine hidrocystoma, sebaceous cyst, epidermal inclusion cyst, hemangioma, lymphangioma, and cystic basal cell epithelioma, as well as malignant lesions such as basal cell carcinoma and malignant melanoma (due to its typical blueblack color).[13456] Eccrine hidrocystoma, in particular, shares the same clinical presentation, anatomical locations, and age predilection. However, they are usually multiple lesions lined by 1–2 layered epithelial lining without any decapitation secretions and myoepithelial cells. Immunohistochemical (IHC) analysis of apocrine hidrocystoma shows positivity for human milk fat globules, gross cystic disease fluid protein 15 (GCDFP-15), cytokeratin (CK) 7, CK 8, CK 18, and CK 19 proteins in the inner layer of epithelium and alpha-smooth muscle actin (a-SMA) and p63 in the outer myoepithelial cells, while negativity for S-100 protein. Contrary to it, eccrine hidrocystoma shows positivity for CK 1, CK 5, CK 10, and CK 14 while negativity for human milk fat globules and GCDFP-15.[124567] Particularly, in long-standing apocrine hidrocystoma, IHC analysis in arriving at a correct diagnosis as increased intraluminal pressure in the cyst wall flattens them and abolishes their characteristic decapitation secretion.[7] Treatment depends on the solitary or multiple nature of the lesion and includes various medical treatment options such as anticholinergic creams, trichloroacetic acid, botulinum toxin, cryotherapy, and, carbon dioxide vaporization laser treatment, especially for multiple lesions and surgical approaches such as simple needle puncture (high chance of local recurrence), surgical excision with clear margins and electrodesiccation.[1267] Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
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Dec 12, 2023
Deirdre M Connolly + 2
Open Access