Erosive Plaques Left Inframammary Area

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Syringocystadenoma papilliferum (SCAP) is a rare, benign, hamartomatous neoplasm of skin arising from pluripotent cells with histologic differentiation in an apocrine pattern. SCAP typically appears at birth or in children and young adults, most commonly on scalp and face, although other sites may also be involved.^[1] SCAP is often associated with organoid naevus (nevus sebaceous) and sometimes with trichoblastoma, apocrine adenoma, apocrine cystadenoma and hidradenoma papilliferum. However, it can also occur de novo.^[1]

A 24-year-old female presented with lesion over the left inframammary area since early childhood which gradually increased in size along with serosanguinous discharge and slight pain in these lesions from the past 3 years. On examination, there were grouped umbilicated erythematous nodule plaque arranged linearly with central ulceration, tender on touch and firm in consistency over the left inframammary area [Figure 1]. Dermoscopic examination showed milky red papillomatous projections with central ulceration, having yellowish lines in reticular pattern and dotted vessels in ulcerated area, white structureless area and peripheral brownish pigmentation [Figure 2].

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Figure 1:

Grouped umbilicated erythematous nodule plaque arranged linearly with central ulceration over the left inframammary area.

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Figure 2:

Dermoscopy (DermLite DL4; 3Gen; San Juan Capistrano, California, USA, non-contact polarised mode, ×10 magnification, images capture with DermLite adapter for iPhone 13) showed milky red papillomatous projections (red arrow) with central ulceration (black arrow), having yellowish lines in reticular pattern (black circle) and dotted vessels in the ulcerated area (yellow arrow head), white structureless area (red star) and peripheral brownish pigmentation (black star).

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Histopathological examination showed mild hyperkeratosis. Upper dermis showed irregular papillary infoldings which are connected to epidermis and is lined by double cell layer with inner columnar cell and outer flat cuboidal cells. Intervening stroma contains dense plasma cell infiltrate admixed with neutrophils [Figure 3a and b]. Hence, a diagnosis of linear SCAP was made.

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Figure 3:

(a) Haematoxylin and eosin stain: upper dermis showed irregular papillary infoldings which are connected to epidermis (black arrows) at 4×. (b) Haematoxylin and eosin stain: papillary infoldings are lined by double cell layer with inner columnar cell and outer flat cuboidal cell (red arrow), intervening stroma contain dense plasma cell infiltrate (black circle) at 40×.

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Plaque type SCAP presents as patchy loss of hair over scalp associated with nevus sebaceous. Linear type presents as skin coloured to erythematous papules with umbilication in a linear arrangement with predilection towards head-and-neck region while solitary popular type manifests as dome-shaped pedunculated lesions with predilection over the trunk. Lesions may increase in size around puberty and can become crusted, verrucous, ulcerated or produce serosanguineous discharge. Although usually benign, SCAP can transform into basal cell carcinoma or ductal carcinoma in up to 10% of cases.^[1]

Linear SCAP is rarely encountered, with very few cases reported in the literature. The majority of cases are de novo and predominantly occur in females. Four cases of linear SCAP have been reported on the chest.^[2]

Dermoscopic features of SCAP include central crater surrounded by white structureless area, shiny white lines, brown structureless area, white rosettes and dotted vessels occasionally.^[3]

There are only few cases describing dermoscopic finding of de novo SCAP. Previously described single case of de novo linear SCAP showed similar findings of milky red papillomatous projections with a central ulceration. In addition, white circles and polymorphic vessels were also seen.^[2] Histopathology is the gold standard for the diagnosis of SCAP.

Differentials in our case were pyogenic granuloma and molluscum contagiosum which can be differentiated on dermoscopy. Table 1 outlines the dermoscopic findings along with histopathological correlation of differentials.^[4,5] In pyogenic granuloma, dotted, linear, irregular and hairpin vessels are typically observed over a red homogeneous area. In contrast, molluscum contagiosum displays radial, punctiform and crown vessels that characteristically do not cross the central core. Unlike both, SCAP exhibits dotted vessels localised within the central crater. Other differential diagnosis can be actinomycosis and deep fungal infection.

However, the reoccurrence is common, surgical excision remains the mainstay of treatment for SCAP, but for lesions in anatomical regions that are not suitable for excision and grafting, carbon dioxide laser treatment may be helpful. This case highlights the rare presentation of SCAP with dermoscopic findings, contributing to the limited literature on this benign yet potentially significant dermatologic entity. Further studies and case reports are essential to broaden the understanding and management of SCAP.