Abstract

Cutaneous calcium deposits such as calcinosis cutis and psammoma bodies are common and well-described in the dermatopathology literature. Calcium oxalate crystals in the skin are significantly less common with few reports to date. Herein, we present a case of concomitant calcium oxalate crystals and psammoma bodies within apocrine glands found incidentally during Mohs surgery. A 97-year-old man presented for Mohs surgery for invasive squamous cell carcinoma on the right helix. Physical exam showed a 1cm hyperkeratotic plaque. Histopathology of the original biopsy specimen showed invasive squamous cell carcinoma. Frozen section completed during Mohs surgery showed poorly differentiated squamous cell carcinoma with invasion into the reticular dermis and polarizable calcium oxalate crystals and nonpolarizable psammoma bodies within apocrine glands. Polarizable calcium oxalate crystals are common in many tissue types including kidney, heart, bone, and thyroid. Calcium oxalate crystals are also commonly reported in benign breast biopsies and are associated with apocrine glands with benign metaplasia. The incidence of calcium oxalate crystals in the skin is unknown. A few cases of calcium oxalate crystals have been reported with apocrine sweat gland tumors. Three common histopathologic subtypes of calcium oxalate deposition include configurations into rosettes, diamond-shaped crystals, or plate-like collections. In this case, calcium oxalate crystals were found in plate-like, geometric collections clustered with psammoma bodies. Psammoma bodies are common entities consisting of lamellar rings of calcium phosphate seen in both benign and malignant skin neoplasms. The co-occurrence of these findings within apocrine glands may indicate a similar underlying etiology and need for further study.

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