What Is the Grayish Nodule on the Right Cheek?

A healthy 55-year-old woman with no prior skin cancer history and no personal or family history of genodermatoses presented with a painless lesion on the right central cheek. The patient was bothered by the lesion’s appearance and slow-growing nature, which prompted her to obtain a skin examination for concern of possible malignancy. 

Physical examination revealed a 1.6-cm × 1.3-cm shiny, violaceous, non-tender nodule with gross telangiectasias on the right central cheek (Figure). Possible diagnoses, risks and benefits of surgical removal, and alternative treatment options were discussed with the patient. 

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Apocrine Hidrocystoma 

Hidrocystomas are benign, solitary, cystic tumors of sweat glands. Classically, they present as translucent papulonodules.¹ Hidrocystomas can be histologically classified as either eccrine or apocrine. They are relatively rare and are more often observed in adults, with a slight predilection for middle-aged and older individuals. Occasionally, they can be observed in certain genodermatoses, such as Schopf-Schultz-Passarge syndrome and Goltz-Gorlin syndrome.² These cysts can equally occur in people of all ethnic backgrounds and genders. The exact prevalence of hidrocystomas is not well-documented, as many cases may go unnoticed or undiagnosed due to their small size and asymptomatic nature.² 

Apocrine hidrocystomas predominantly emerge from apocrine sweat glands, commonly found in regions with dense hair follicles. The most common location for this entity is on the face and scalp, as well as on the neck and trunk region. Less commonly, apocrine hidrocystomas have been reported in other regions with apocrine glands, including the penis, axilla, palms, soles, and perianal areas.³ These cysts manifest as small, translucent or bluish nodules with a characteristic dome-shaped appearance, ranging from 3 to 15 mm.⁴ While generally painless, less commonly, individuals may experience mild tenderness or discomfort. Despite being mostly asymptomatic, individuals may occasionally report a sense of fullness or mild pain in the affected area.³ 

Conversely, eccrine hidrocystomas arise from eccrine sweat glands, predominantly on the face, especially around the eyelids, forehead, and cheek.^5,6 Manifestation in less common regions, such as the trunk, extremities, and genitalia, have also been reported, with reports mentioning cases on the vulva.^6,7 Solitary cysts are referred to as Smith type, whereas multiple cysts are referred to as Robinson type. These cysts present as small, clear or bluish nodules, typically measuring 1 to 6 mm.⁴ Hidrocystomas may present in atypical locations or be larger than normal in size, which should prompt histopathologic examination to differentiate them from malignant neoplasms, such as basal cell carcinoma (BCC) and amelanotic melanoma. 

Both apocrine and eccrine hidrocystomas share common histopathologic features, such as a cystic architecture and clear fluid content. Apocrine hidrocystomas typically present with cystic structures lined by an outer layer of myoepithelial cells and the inner layer containing cuboidal or columnar cells. The cysts are filled with eosinophilic material, often demonstrating decapitation secretion^.8 

In contrast, eccrine hidrocystomas are lined by a single layer of cuboidal or flattened epithelial cells. These cells are similar to the luminal cells of normal eccrine ducts. The cystic spaces contain clear fluid, reflecting the eccrine gland’s characteristic secretion. The absence of a double layer, as seen in apocrine hidrocystomas, and lack of decapitation secretion distinguishes eccrine hidrocystomas histologically.² See Table 1 for a summary of the differences of the 2 entities and their possible differential diagnoses. See Table 2 for a summary of how to differentiate these differentials based on histology. 

Hidrocystomas are usually sporadic and not associated with specific syndromes. However, there are inherited disorders commonly associated with multiple apocrine/eccrine hidrocystomas. Schopf-Schulz-Passarge syndrome, an autosomal recessive disorder, is marked by having multiple periocular apocrine hidrocystomas. The syndrome can also be characterized by hypotrichosis, palmoplantar hyperkeratosis, and hypodontia^.2 

Similarly, Goltz-Gorlin syndrome (nevoid BCC syndrome) can have a spectrum of features, including multiple periocular apocrine hidrocystomas. Other features of this syndrome include skeletal abnormalities, malformed ears, and microcephaly.² 

On the other hand, the presence of multiple eccrine hidrocy-stomas has been shown to be linked to Graves’ disease, possibly stemming from the symptom of hyperhidrosis. Therefore, treatment of hyperthyroidism in these individuals has been shown to lead to an observed disappearance of the lesions.⁹ 

These associated symptoms and syndromes are important to consider when dealing with hidrocystomas; however, our patient presented with a singular nodule and no other symptoms, suggesting a standalone diagnosis of hidrocystoma. It is important to consider personal and family history when approaching diagnosis. 

The primary treatment for apocrine hidrocystoma involves surgical excision with narrow margins. This allows for both diagnosis confirmation and definitive treatment. However, this may result in cosmetically unacceptable scarring if located on the face. Incision and drainage may also be a viable option, but additional electrosurgical destruction of the cyst wall is often recommended to prevent recurrence.² 

Developments involving hidrocystomas have opened new directions for their treatment. Ablative CO2 lasers can be used in the treatment of multiple apocrine hidrocystomas with a more favorable cosmetic result in terms of scarring and recurrence.¹⁰ Trichloroacetic acid has also been utilized as an alternative method, with follow-up appointments demonstrating no recurrence and cosmetically favorable outcomes.^11,12 Additionally, botulinum toxin A injection has been effective in managing multiple or recurrent hidrocystomas, leading to improvement in some cases with repeat treatments, as well as sustained flattening of the lesion at follow-up appointments with no risk of scars.¹³ These new treatment options offer potential noninvasive alternatives to surgery. However, these alternative methods must be further studied as their level of evidence is limited to descriptive accounts of individual cases or a small number of cases. Conducting systemic reviews on these methods can lead to a stronger clinical recommendation for their use. 

The patient is an otherwise healthy woman with a solitary apocrine hidrocystoma. Given the benign nature of the lesion and the absence of symptoms, the decision to observe and conservatively manage the lesion was undertaken. The patient was offered surgical excision or laser ablation if she decided to undergo definitive treatment later. 

This case report discusses the clinical presentation, diagnostic approach, histologic features, and treatment options of apocrine hidrocystomas. Although they are benign cystic lesions, clinical presentation in an atypical location may be concerning for cutaneous malignant neoplasm. Histologically, apocrine hidrocystomas exhibit a double layer of epithelial cells, confirming their apocrine origin. Treatment options include surgical excision, incision and drainage, and innovative approaches such as ablative CO2 laser and botulinum toxin A injection. 

Dr Baiyasi is a PGY1 at Henry Ford Hospital in Detroit, MI. Dr Osto is a PGY3 at University of Maryland School of Medicine in Baltimore, MD. 

Dr Khachemoune is the Derm DX section editor and a dermatologist affiliated with SUNY Downstate and VA New York Harbor Care-Brooklyn in Brooklyn, NY. 

Disclosure: The authors report no relevant financial relationships. 

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