Co‐Existence of a Syringocystadenoma Papilliferum and Tubular Apocrine Adenoma in the Absence of a Nevus Sebaceus: A Case Series and Review of the Literature

BACKGROUND: Syringocystadenoma papilliferum (SCAP) and tubular apocrine adenoma (TAA)/papillary eccrine adenoma (PEA) are rare, benign sweat gland tumors that most commonly co-occur in the setting of a nevus sebaceus. Some hypothesize that these tumors exist on a spectrum; however, their co-existence without a nevus sebaceus is infrequently reported. METHODS: We searched our dermatopathology laboratory database (2001-2006) for cases of co-occurring SCAP and TAA or PEA without an associated nevus sebaceus and performed a PubMed literature review to identify previously published cases. Data were extracted on patient age, gender, anatomic location, and immunohistochemistry findings. RESULTS: Eight cases were identified at our institution, all in female patients (mean age 43 years). Sites included the scalp (n = 4), mons pubis (n = 2), arm (n = 1), and buttock (n = 1). Five of the eight cases tested demonstrated BRAF V600E positivity in both the SCAP and TAA components. The literature review identified 15 publications reporting 38 cases, with similar IHC findings between SCAP and TAA/PEA; no study reported on BRAF findings. CONCLUSIONS: We present one of the largest single-institution series of co-existing SCAP and TAA/PEA without nevus sebaceus. The consistent co-occurrence of these tumors and overlapping molecular profiles supports the hypothesis that SCAP and TAA/PEA may exist on a histologic continuum.