Syringocystadenoma Papilliferum
Key Points
Syringocystadenoma papilliferum (SCAP) is a benign adnexal skin tumor presenting as a proliferating lesion of apocrine, eccrine, or pluripotential appendageal cells, mostly located on the head and neck
It is associated with nevus sebaceous of Jadassohn in 40% of cases
Human papillomavirus (HPV) DNA and mutations in the RAS/mitogen-activated protein kinase signaling pathway have been detected in both sporadic cases and lesions arising in nevus sebaceous
SCAP may present as a flat, flesh-colored or dark brown plaque with a smooth or raised verrucous or papillomatous surface
Papular lesions are skin-colored to pink or reddish, and when multiple they are usually arranged in a linear configuration
Symptoms include an enlarging mass, localized eyelid swelling, pruritus, discomfort, and bleeding
Treatment most often is by complete surgical excision with clear margins
The prognosis of SCAP is good following surgical excision, and recurrence is uncommon
In 1917, John Stokes described a cutaneous neoplasm on the thigh of a patient that he termed naevus syringadenomatosus papilliferus.1 Additional early cases were added by Biberstein,2 Reuterwall,3 and Sachs and Lewis.4 Since then, several hundred additional cases have been reviewed from the literature, and several large series have reviewed these cases.5,6,7
Syringocystadenoma papilliferum (SCAP) is a benign adnexal skin tumor presenting as a proliferating lesion of the apocrine or eccrine type of differentiation. It is located on the head and neck in 75% of cases, followed by the trunk (20%) and the extremities (5%), especially the lower limbs.5,6,7 More than half of these tumors are present since birth,6 although most cases present for medical attention 2 to 4 decades later.
The mean age at presentation for SCAP is 45 years with a range of 8 to 82 years.6 In patients with a known duration of symptoms, the lesions were present for 2 to 70 years with an average of 23 years. Most lesions enlarge slowly over time, but a small number of tumors may show accelerated growth over several months. In younger patients, the lesions present as a cluster of papules or small nodules, often with a cystic component.8
SCAP has been associated with other benign adnexal neoplasms including tubulopapillary hidradenoma, apocrine cystadenoma, hidrocystoma, eccrine spiradenoma, apocrine adenoma, poroma folliculare, apocrine acrosyringeal keratosis, verrucous cyst, trichoepithelioma, trichilemmoma, sebaceous epithelioma, condyloma acuminatum, acanthoma, and nevus sebaceous.9,10,11,12,13 However, most often it is associated with nevus sebaceous of Jadassohn (Chapter 96) where 40% of histologically documented cases show SCAP contiguous with a nevus sebaceous.5,6 Cases arising from nevus sebaceous are more frequently associated with malignancy, and about 9% of SCAP is associated with basal cell carcinoma.5,6 The well-known relationship between basal cell carcinoma and nevus sebaceus14 suggests that the occurrence of BCC may not always be etiologically related to the SCAP but to the nevus sebaceous. However, several reports suggest that SCAP can transition to basal cell and squamous cell carcinoma.5,15,16,17,18,19
Syringocystadenocarcinoma papilliferum (SCACP) is a rare malignant tumor of apocrine glands that most often arises in association with SCAP.20,21,22,23 It is typically described as a long-standing lesion, most commonly on the head and neck of middle-aged or elderly individuals.20,24,25 Lesions usually are raised and nodular and may be associated with ulceration, secretion, or pain.25,26 One case of SCACP of the eyelid was reported with orbital invasion, requiring orbital exenteration.27 Verrucous carcinoma is another tumor that has been associated with SCAP in a small number of patients.28,29 This tumor is classified as a low-grade, extremely differentiated, squamous cell carcinoma with a propensity for localized growth and recurrence.30
Etiology and Pathogenesis
Decapitation secretion of the glandular epithelium is seen in SCAP, suggesting that SCAP is of apocrine origin. However, although light microscopy suggests an apocrine origin of SCAP, immunohistochemistry and electron microscopy have yielded conflicting data, with some authors documenting eccrine characteristics in this tumor.6,11,32,36 Several theories have been advanced to reconcile these conflicting observations and to explain the range of other neoplasms associated with SCAP. Mammino and Vidmar6 suggested that perhaps the final answer is that SCAP develops from pluripotential
appendageal cells. An alternative theory involves the derivation of SCAP from a hybrid-type gland described as an apoeccrine gland.37,38 This type of gland exhibits microscopic, immunohistochemical, and ultrastructural features that combine both eccrine and apocrine elements, including decapitation secretion.
appendageal cells. An alternative theory involves the derivation of SCAP from a hybrid-type gland described as an apoeccrine gland.37,38 This type of gland exhibits microscopic, immunohistochemical, and ultrastructural features that combine both eccrine and apocrine elements, including decapitation secretion.
Although the pathogenesis of SCAP remains unclear, in both sporadic cases and lesions arising in nevus sebaceous, the human papillomavirus (HPV) DNA and mutations in the RAS/mitogen-activated protein kinase signaling pathway have been detected. BRAF V600E and HRAS mutations are the most common molecular alterations found in sporadic SCAP. The detection rate of HRAS mutation has been reported in 10%-26.1% of SCAP lesions,39,40,41 and the frequency of BRAF mutations reported in 40%-66.7% of cases.39,41,42 These suggest an etiologic role in the pathogenesis of SCAP.
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