McMullen ER, et al. - Researchers sought to ascertain the specificity of fine calcium deposits in vessel walls (identifiable on von Kossa [VK] stain only) and other extravascular calcifications via retrospectively investigating and differentiating the clinicopathologic features in calciphylaxis (n = 27), gangrene and viable skin at amputation margin (n = 20 each), chronic stasis (n = 22), and thrombotic vasculopathy (n = 19). In this work, optimal sensitivity (85%) and specificity (88%) for calciphylaxis were achieved with combining calcium deposits detected by VK and thrombosis of subcutaneous small vessels. Similar observations applied to medium-sized vessel calcification. In calciphylaxis, they exclusively identified diffuse dermal angiomatosis. Outcomes thereby support the utility of VK in enhancing the detection of vascular calcification and avoiding the false-negative diagnosis, however, this finding demands concomitant subcutaneous small vessel thrombosis to support a diagnosis of calciphylaxis. Increased suspicion for underlying calciphylaxis was supported with identification of diffuse dermal angiomatosis and prompt deeper sampling is recommended in the appropriate clinical setting.