Metastatic endometrial endometrioid carcinoma mimicking pilomatrixoma of the distal vagina.

Endometrioid carcinoma with a prominent squamous component has the ability to mimic pilomatrixoma. One previous case is documented of cutaneous metastasis in the upper limb derived from ovarian endometrioid carcinoma mimicking pilomatrixoma. Here, we describe a case of metastasis of endometrial endometrioid carcinoma in the distal vagina, treated with radiotherapy and later resected. The histology of the lesion was thought initially to represent pilomatrixoma; this has not previously been described in the vagina, where no hair matrix cells are normally present. We hypothesise that radiotherapy may have effectively 'sterilised' the glandular component, blinding the malignant features. Further management was significantly altered by the reinterpretation of this result as metastatic disease. We emphasise that in the context of known endometrioid carcinoma, the diagnosis of pilomatrixoma should be made with caution, particularly where radiotherapy has been used. 2017 BMJ Publishing Group Ltd.