A 62- year-old man requests the removal of an irritated growth on his back. During a skin examination, a protuberant reddened nodule on the patient’s scalp is found that was partially covered by hair. He states that this lesion has been present since birth and has recently started to enlarge but has remained asymptomatic and only bleeds when accidentally grazed by his barber. He is in good health and on no oral medications except low-dose finasteride to prevent hair loss.
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Syringocystadenoma papilliferum (SCAP) is a rare, benign, adnexal neoplasm that typically presents as a single, red to brown plaque. The lesion may have ulcerations, crusting, and serous drainage or a wart-like appearance. It may present as small papules with linear distribution or arise within a sebaceous nevus.1 A sebaceous nevus is a hamartoma of the apocrine sweat gland that most commonly presents at birth. Sebaceous nevi and SCAP are characteristically found on the head or neck; a case report documents occurrence in the supragluteal region.2 The etiology of SCAP is unknown. Sporadic cases have been linked to BRAF V600E mutation.3
Differential diagnosis of SCAP may include sebaceous nevus, epidermal nevus, or aplasia cutis congenita. Dermoscopy is nonspecific with polymorphous vessels as a prevalent feature.4 Histopathology is characterized by invaginated papillations that connect to the surface squamous epithelium containing 2 layers: columnal to cuboidal (inner layer) and basal/myoepithelial cells (outer layer).1
SCAP may undergo malignant transformation to basal cell carcinoma or, less commonly, squamous cell carcinoma.2 Other reported transformations of SCAP include syringocystadenocarcinoma papilliferum, hidradenoma papilliferum, verrucous carcinoma, condyloma acuminatum, and apocrine adenoma. The treatment of choice is full excision of the lesion.
Stephen Schleicher, MD, is director of the DermDox Center for Dermatology in Pennsylvania, associate professor of medicine at Commonwealth Medical College, and clinical instructor of dermatology at Arcadia University and Kings College. Sarah Jacobs, PA-C, is a graduate of Kings College.
1. Foreman RK, Duncan L. Appendage tumors of the skin. In: Kang S, Amagai M, Bruckner AL, et al eds. Fitzpatrick’s Dermatology. 9th ed. McGraw-Hill.
2. Singh M, Choudhary S, Chaurasia J. Well-differentiated squamous cell carcinoma arising in syringocystadenoma papilliferum. Indian Dermatol Online J. 2019;10(2):168-170. doi:10.4103/idoj.IDOJ_43_1
3. Al Hawsawi K, Alharazi A, Ashary A, Siddique A. Syringocystadenoma papilliferum: a case report and review of the literature. Case Rep Dermatol. 2019;11(1):36-39. doi:10.1159/000497054
4. Lombardi M, Piana S, Longo C, et al. Dermoscopy of syringocystadenoma papilliferum. Australas J Dermatol. 2018;59(1):e59-e61. doi:10.1111/ajd.12654