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Case Reports

Abstract

We present a case of extra-vulvar adenocarcinoma with mammary-type features. The patient, a Caucasian woman in her 80s with no prior history of cancer, noticed an enlarging nodule on her scalp in 2001 which was biopsied and interpreted as ER+/PR+/HER-2neu- metastatic breast adenocarcinoma. Thorough workup including PET-CT, breast MR, and US failed to identify a primary breast cancer. Despite hormone therapy and surgical excision, the patient had multiple local recurrences and eventual cervical lymph node metastasis. In each instance of recurrence histopathologic examination demonstrated neoplastic cells in infiltrative cords, strands of glandular epithelium with ductal differentiation, and associated stromal desmoplasia consistent with adenocarcinoma. The persistent absence of a primary breast lesion and recent recurrence prompted further investigation into the possibility of adenocarcinoma with mammary-type features. The neoplasm was immunoreactive for ER, KRT7, TRPS1, and GCDFP-15 (weak). It was negative for PR, AR, BerEp4, D2-40, KRT5, mammaglobin, and p63. Genomic profiling for hereditary breast cancer was unremarkable. In summary, these findings were suggestive of adenocarcinoma with mammary-type features and treatment with palbociclib was initiated. This diagnosis is rare and the etiology is unclear, though malignant transformation of ‘anogenital mammary-like’ glands versus ‘native apocrine’ glands has been raised.  To our knowledge, this entity has been exclusively reported to arise from the vulva. The unique presentation on the scalp further complicates our understanding of this exceedingly uncommon disease and attempts to characterize it.