Syringocystadenoma Papilliferum of the Scalp Mimicking Squamous Cell Carcinoma

Background: Syringocytadernoma papilliferum (SCAP) is a rare benign tumour of the apocrine or eccrine sweat glands. Predominantly a tumour of childhood. SCAP usually presents as a solitary papule, nodule, or plaque on the scalp. However, cutaneous adnexal tumours may bring diagnostic difficulties to dermatologists in everyday practice. We are presenting a case of SCAP, which we previously diagnosed clinically as squamous cell carcinoma. Case presentation: A 33 years old female with ten years history of a skin lesion on the scalp, which bleeds easily when touched. The lesion consisted of a red crusted nodule measuring 3 cm by 1.5 cm on the right parietal region. Dermoscopically, we saw white circles and scales. We made a clinical diagnosis of squamous cell carcinoma, and we did a wide surgical excision. The histology results showed features of SCAP. Conclusions: With any tumour on the scalp with a long-standing history, especially in the middle-aged group, SCAP needs to be among the differential diagnoses. SCAP may mimic other cutaneous tumours, especially squamous cell carcinoma and basal cell carcinoma. Clinical and Experimental Dermatology and Therapies Chapa PJ, et al. Clin Exp Dermatol Ther 6: 171. www.doi.org/10.29011/2575-8268.100171 www.gavinpublishers.com


Introduction
Syringocystadenoma papilliferum (SCAP) is a benign tumour of apocrine or eccrine sweat glands predominantly in infancy or childhood. It usually occurs in the head and neck region, and it is rare. It can arise de novo without any preexisting lesion, but it can arise or coexist with both benign and malignant tumours [1]. SCAP usually manifests as a solitary papule or a nodule and, less frequently, in the form of multiple oozing, crusted papules, or nodules grouped, forming a plaque or a cutaneous horn [2]. The appearance of SCAP is often misdiagnosed clinically as a basal cell carcinoma (BCC) [3] or squamous cell carcinoma (SCC). We are presenting a case that we clinically misdiagnosed as SCC of the scalp, but later the histopathology revealed SCAP diagnosis.

Case presentation
A 33-year-old lady presented with a ten-year history of swelling on the scalp. Initially, the patient started noticing a bleeding ulcer after combing hair on the right parietal region at 23 years. Later she saw a growth in that region, which was bleeding easily when touched. She was managed with several antibiotics and systemic steroids with mild improvement. On examination, she had a mobile crusted nodule on the right parietal region measuring 3 cm in length by 1.5 cm in breadth with hair loss (Figure 1  There was no regional lymphadenopathy seen. Dermoscopically, we saw white circles and scales ( Figure 2). We made a clinical diagnosis of squamous cell carcinoma, and the plan was to do wide excision and send tissue for histopathology. We operated under local anaesthesia and removed the whole tumour with a margin of 0.5 cm and depth up to hypodermis ( Figure 3). The histopathological examination ( Figure 4) showed epidermal cystic invagination lined by squamous epithelium with a transition of epithelial lining with two cell layers, papillary projections, decapitation, and numerous plasma cells. Nevus sebaceous was seen on the lesion. All the margins were free. These findings were diagnostic of SCAP.

Discussion
SCAP is a rare benign lesion arising from the pluripotent cells from either apocrine or eccrine lineage. They most commonly arise from apocrine glands. It usually affects the head Volume 6; Issue 02 Clin Exp Dermatol Ther, an open access journal ISSN: 2575-8268 and neck, taking its origin either de novo or from a preexisting nevus sebaceous in 30% of the cases [4]. Three clinical types of SCAP have been described. The first one is plaque-type, occurs on the scalp as a hairless lesion, which can be present from birth, and after that, increases during the onset of puberty into a nodular or verrucous entity. A linear type usually manifests with multiple papules of similar size, with a dimple, often being misdiagnosed as molluscum contagiosum (MC). The last, a solitary nodule, usually presents on the trunk, perhaps on the genitalia, shoulders, or axillae [5]. One-third of SCAP cases are associated with a nevus sebaceous, as was found in our case. BCC development has been reported in up to 10% of the cases but much less frequently with SCC [6]. Our patient had features suggestive of SCC.
The dermoscopic examination of SCAP usually contains yellowish-white discolouration, hairpin-like, glomerular, and linear vessels with a surrounding pinkish-white rim and peripheral hairpin-like vessels [4]. These features resemble those found in BCC, SCC and seborrheic dermatitis. Some of these features, such as white circles, which are features of SCC, were found in our case, which made the diagnosis of SCAP more difficult.
The nodular type of SCAP may mimic a BCC [1] or even SCC. Our case had a plaque-type of SCAP, which made us diagnose it as SCC instead of SCAP. Dermatologists should have a high index of suspicion when a scalp tumour resembling SCC is seen. SCAP should be among the differential diagnoses. A punch biopsy or surgical excision for histopathological examination of the lesion should be performed to confirm or rule out the diagnosis of SCAP or malignant condition such as SCC or BCC.

Conclusions
Clinicians need to recognize these rare tumours because a correct diagnosis will lead to proper management, which will prevent anxiety from the patient. Therefore, we advise wide excision or punch biopsy of the suspected SCAP, SCC or BCC on the scalp for histopathological examination to confirm or rule out these diagnoses.

Declarations Ethical Considerations
We explained the purpose of the study to the participant, and to ensure voluntary participation, her participation was requested. After agreeing to participate, she signed informed consent.

Data Availability
The data used during the preparation of the case report are available from the corresponding author upon request.