Abstract:

While syringocystadenoma papilliferum (SCAP) is known to most general pathologists, its malignant counterpart, syringocystadenocarcinoma papilliferum (SCACP), is an extremely rare entity. Unlike SCAP, which in the majority of cases is present prior to puberty, SCACP is usually diagnosed in middle-aged or elderly adults. In keeping with SCACP arising out of SCAP, SCACP is encountered most frequently in the head and neck with the scalp being the most common site. In contrast to the well-described association of SCAP with mutations in genes of the mitogen-activated protein kinase (MAPK) pathway, none of the SCACP reports include next-generation sequencing (NGS) data except for a single report of a metastasis assumed to have arisen in SCAP. Herein, we comprehensively review the literature and present a case of SCACP that adds to the literature in several ways. This 0.7 x 0.7 x 0.2 cm lesion from the scalp of a 90-year-old gentleman is one of the smallest and reported in one of the oldest patients. The lesion was likely detected shortly after invasion so the entire spectrum from SCAP through in situ carcinoma to invasion can be appreciated within the silhouette of the underlying benign adnexal neoplasm. The carcinomatous component is primarily in the central part of the lesion and the periphery shows a well-circumscribed contour with a tubular apocrine adenomatous appearance. This highlights the importance of examining lesions assumed to be SCAP on high power as they can appear benign on low power. We also report the results of comprehensive genomic profiling of the tumor.

Financial Disclosure:
No current or relevant financial relationships exist.

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Maryam Abdo, MBChB