Eccrine Syringofibroadenoma: A Rare Skin Adnexal Tumor at a Rare Site

Dear Editor,

Eccrine syringofibroadenomas (ESFAs) are rare benign skin adnexal tumors (SATs) that arise from cells of the acrosyringium of eccrine sweat glands.[1] Clinically, varied phenotypes have been reported but histological findings of ESFA are classical, enabling the dermatologist to arrive at a conclusive diagnosis.

The three characteristic findings identified on histopathology in ESFA include:

• Narrow strands of basaloid acrosyringeal cells arranged as anastomosing cords extending into the dermis.

• Duct formation.

• Mucinous fibrovascular stroma.

Our patient was a 25-year-old male, who presented with an asymptomatic, pinkish white fibrotic nodule over the scalp of size 2 × 2.5 cm [Figure 1]. He noticed this since the past 7 months and the lesion had gradually progressed to attain the current status. A provisional diagnosis of fibroma and SAT were considered and an excision biopsy was performed. Skin biopsy revealed thin anastomosing cords of epithelial cells arising from the epidermis and extending toward the dermis [Figures 2 and 3].

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Figure 1

A solitary pinkish white fibrotic nodule on the scalp

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Figure 2

Thin anastomosing cords of epithelial cells arising from the epidermis and extending to the dermis (H&E ×40)

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Figure 3

Higher magnification of anastomosing cords composed of epithelial cells (H&E ×100)

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A ductule lined by cuboidal cells was also identified in association with the epithelial strands suggesting eccrine differentiation [Figure 4]. With the aforementioned findings, a diagnosis ESFA was confirmed.

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Figure 4

A ductule lined by cubical cells in association with epithelial strands, suggesting eccrine differentiation (H&E ×100)

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Five clinical subtypes of ESFA exist; namely:

• Solitary ESFA;

• Multiple ESFA associated with ectodermal dysplasia;

• Multiple ESFA without cutaneous features;

• Unilateral linear ESFA; and

• Reactive ESFA associated with inflammatory or neoplastic dermatosis.

Our patient belonged to the solitary ESFA subtype. Past medical literature elaborates very few reports on solitary non-reactive ESFAs; details of which have been outlined in Table 1.

After studying the above reports (pertaining to solitary ESFA), we observed that the extremities constituted the most common site of involvement. Scalp involvement, on the other hand was described in only one previous publication.[9] We would hereby like to highlight our case firstly, owing to the rare fibrotic nodular morphology encountered and secondly its involvement of the scalp (an uncommon site for ESFA).

Histopathology findings reported in our patient were classical for this entity and that enabled clinching the diagnosis. Immunohistochemistry, though not mandatory with this classical histopathology may be required for diagnosis in some less typical presentations to confirm eccrine origin of the SAT.

To conclude, all dermatologists should be familiar with the histopathological pattern of ESFA, so that the diagnosis of ESFA is not missed. The standard treatment for solitary ESFA is surgical excision.