Pseudoxanthoma elasticum-like change adjacent to a benign adnexal neoplasm: a histopathologic reaction pattern

The progressive calcification and fragmentation of elastic fibers, primarily affecting the skin, are histopathologic features typically associated with pseudoxanthoma elasticum (PXE), pseudo-pseudo PXE, or even acquired PXE. We present a case of a 65-year-old woman, with a known history of breast carcinoma, status after wide excision (T1N0Mx) in 2010, who presented with a 0.6 × 0.5-cm, nontender pink nodule in the right inferior axilla of 1 week duration on the same side as her mastectomy. Histopathologically, the lesion revealed a circumscribed, nonencapsulated bland dermal tumor with poroid and clear cells and foci of ductal differentiation-features diagnostic for hidradenoma. Of note, immediately adjacent to the hidradenoma, the specimen also exhibited short, frayed elastic tissue fibers (positive for EVG and Von Kossa stains)-features reminiscent of PXE. With this case, we expand the spectrum of reaction patterns observed in the skin to include a PXE-like change, a reaction pattern that, to the best of our knowledge, has not been previously reported in association with a benign cutaneous tumor.