Milium-like syringoma: a case study on histogenesis

BACKGROUND: Milium-like syringoma is a variant of syringoma first described in 1987. Only few cases have been reported in the literature. It may be misleading clinically, and its histogenesis has not been clarified. CASE REPORT: We present a case of periorbital milium-like syringoma, with studies on the histopathologic, histochemical, and immunohistochemical features. RESULTS: Histology showed a large keratin-filled cyst in the upper portion of the lesion approximating the epidermis. Serial sections revealed that the cyst connected with the underlying syringomatous epithelial strands. Melanin was absent in the wall of the cyst, as demonstrated by Fontana-Masson stain. Cytokeratin 7 was expressed neither in the milia nor in the solid epithelial parts. Carcinoembryonic antigen (CEA) reactivity was seen in the luminal cells of the keratinous cysts. However, in the largest keratin-filled cyst clinically suggesting a milium, only the lower half of the cyst was positive for CEA. These results proved that the milia were part of syringoma with eccrine duct differentiation. Fusion of the upper half of the largest cyst with the epidermis may explain the absence of CEA positivity in this part, analogous with eccrine duct milia. Review of the literature indicated that this variant of syringoma occurs more often in Asians. CONCLUSION: We present evidence, and propose the histogenesis of milium-like syringoma, that it is a variant of syringoma with a prominent cystic component showing features of eccrine duct milia. Recognition of its nature is of therapeutic significance. Further studies are required to verify its clinical characteristics as compared with ordinary syringomas.