Solitary eccrine syringofibroadenoma with nail involvement: A rare entity.

Eccrine syringofibroadenoma (ESFA) is a rare, benign tumor of eccrine sweat gland origin that usually presents as a nodule on the extremities of an elderly person. It can also present as an ulcerative plaque, verrucous lesion, papular or nodular lesion or as palmoplantar keratoderma. Although the clinical features are variable, histology is characteristic in the form of anastomosing strands, cords and columns of epithelial cells embedded in a fibrovascular stroma. We report the case of a 62-year-old male with a nodular lesion on the extremity that caused secondary involvement of the nail in the form of complete nail dystrophy. The histology showed features consistent with ESFA. Nail involvement by ESFA is a rare presentation and is rarely described in the literature.

What was known?

Eccrine syringofibroadenoma is a benign tumor of sweat glands that is rarely encountered in clinical practice. It can present as a nodule, plaque or verrucous lesion and the histology is characteristic.

Introduction

Eccrine syringofibroadenoma (ESFA) is a rare benign tumor that originates from the excretory portion of eccrine sweat gland.[1] It is characterized by variable clinical features but classical histological findings in the form of slender, anastomosing epithelial cords of acrosyringeal cells resembling fibro-epithelioma of Pinkus, duct formation, and a mucinous fibrovascular stroma. The tumor appears as a solitary, hyperkeratotic, nodular plaque on the extremities in the elderly.[2] The lesion can be verrucous, ulcerative, nevoid or linear. Multiple lesions have been associated with hidrotic ectodermal dysplasia and Schopf's syndrome.[34] We herein report a case of solitary nodular ESFA on the hand of an elderly male that resulted in nail dystrophy. Such kind of nail involvement is rarely described in the literature.

Case Report

A 62-year-old male came to our outpatient department complaining of a slowly enlarging painful swelling over the left index finger of 1 year duration. The pain was intermittent and radiated to the left wrist. There was no history of diabetes mellitus or any other cutaneous lesion. Examination revealed a sharply demarcated nodular plaque with thick adherent scale over the skin on the distal phalanx of left index finger. The lesion had a warty, keratotic surface [Figure 1]. The nail showed complete dystrophy. X-ray of the involved hand revealed soft tissue swelling in index finger with partial resorption of tip of distal finger phalanx.

Figure 1

Warty keratotic plaque with secondary nail dystrophy

A punch biopsy performed from the lesion was sent for histological examination that demonstrated an acanthotic epidermis with reticulate proliferation of malphigium layer extending into the dermis in the form of branching anastomosing strands [Figure 2a]. These strands, 2-4 cell layers in thickness, were seen extending from multiple points in the epidermis. Also, identified were small ductules lined by cuboidal cells within the epithelial strands. These ductules are indicators of eccrine differentiation. The dermis entrapped between the epithelial strands is mildly cellular fibrovascular in appearance [Figure 2b].

Figure 2

(a) Branching anastomosing strands of epithelial cells extending from multiple points in the epidermis (H and E, original magnification ×40. (b) Small ductules lined by cuboidal cells within the epithelial strands embedded in a fibrovascular stroma (H and E, original magnification ×400)

The tumor cells reacted with PAS stain.

The lesion was completely excised by the general surgeon and sent for histopathological examination which confirmed the above findings.

Discussion

ESFA was first described by Mascaro among a series of lesions diagnosed as fibroepithelial tumor of Pinkus.[5] It is a rare benign tumor of the excretory portion of eccrine sweat gland. The clinical presentation is variable and can range from solitary to multiple papules or nodules usually in the elderly. Site of predilection is the extremity although it can affect the face, back, abdomen, buttocks and rarely the nails. Starink, in 1997, divided ESFA into four types based on the clinical manifestations.[3] Subsequently, French added another type to this classification.[6] ESFA can be classified into:

Solitary ESFA

Schopf syndrome (multiple ESFA associated with hidrotic ectodermal dysplasia)

Syringofibroadenomatosis (multiple ESFA without associated cutaneous findings)

Non-familial unilateral linear ESFA (nevoid ESFA), and

Reactive ESFA-associated inflammatory or neoplastic dermatoses.[78]

Of these, solitary ESFA is the most common and presents as a skin-colored papule, plaque or nodule on the extremity.

ESFA can occur as a reactive proliferation associated with other conditions like venous stasis, skin ulcer, chronic lymphedema, burn scar, nevus sebaceous, bullous pemphigoid, epidermolysis bullosa. ESFA in such conditions could arise due to hyperplasia occurring as a result of remodeling of skin structures induced by trauma.

ESFA is characterized by three main histologic features:

Proliferation of anastomosing cords and strands of basaloid acrosyringeal cells in a pattern similar to that seen in fibroepithelioma of Pinkus

Duct formation, and

Mucinous fibrovascular stroma.

Histologic differential diagnosis includes reactive eccrine duct proliferation or hyperplasia, fibroepithelioma of Pinkus, eccrine poroma, eccrine papillary adenoma. In cases of reactive eccrine duct proliferation, the underlying disease is usually clearly demonstrable which was absent in this case. Conditions such as deep fungal infections may exhibit reactive eccrine duct proliferation in association with pseudoepitheliomatous hyperplasia. Fibroepithelioma of Pinkus contains horn cysts, small buds, columns of basaloid cells in a loose myxoid stroma. Eccrine poroma closely resembles ESFA as both contain broad anastomosing bands of epithelial cells. Tumor cells of eccrine poroma contain significant amounts of glycogen associated with cytoplasmic clearing. The stroma is hyalinized. Eccrine papillary adenoma shows dilated tubules lined by eccrine ductal cells with intraluminal papillary proliferation which were not seen in our case.

The histogenesis of this entity is controversial. Many authors suggest an acrosyringeal differentiation though eccrine duct origin has been suggested based on cytokeratin expression.[91011]

Our case fits into solitary ESFA. The secondary nail involvement that was seen has been rarely reported.[1213] The lesion was subsequently excised by the general surgeon and there was no evidence of any recurrence during 1-year follow up. There are reports of carcinomatous transformation of ESFA; hence, every case should be followed in view of this risk of developing carcinoma.[14]

what is new?

Secondary nail involvement in the form of nail dystrophy due to ESFA is rare. The diagnosis of ESFA should be kept in mind when an elderly patient presents with nodule over the extremity and nail findings should not be overlooked.