RESUMEN
BACKGROUND: Extramammary Paget's disease (EMPD) is a rare neoplasm that commonly affects post-menopausal women. It usually presents in the anogenital area where apocrine sweat glands are abundant, most commonly in the vulva. The disease is characterised by slow growth and high local recurrence rates. Clinically, EMPD presents as well-demarcated erythematous lesions or plaques that may be ulcerated. Microscopically, it shows a group of atypical cells with abundant clear cytoplasm and nuclear pleomorphism. METHODS: We present the case of a 58-year-old female with a history of poorly differentiated squamous cell carcinoma of the cervix, status post-radical-hysterectomy with bilateral salpingo-oophorectomy, and chemoradiation in 2016. The patient also had a long-standing history of vulvar pain, skin changes on her left labia, and itching. RESULTS: Punch biopsies of the vulva revealed acanthosis and acantholysis of the epidermis with an intraepidermal scattering of single, or clusters of, large cells with round/oval nuclei and abundant clear cytoplasm. The cells were positive for p16, CK19, CK7, and PAX8, supporting the diagnosis of EMPD without evidence of dysplasia. The concurrent Papanicolaou smear showed a hypercellular specimen composed of hyperchromatic tissue fragments with high nuclear-to-cytoplasmic ratios and apoptotic bodies. The presence of intracytoplasmic mucin and the tridimensionality of the fragments supported the diagnosis of adenocarcinoma. CONCLUSIONS: This study compares the histological and cytomorphological features of EMPD with high-grade squamous intraepithelial lesions, since the pathogenesis, precursor lesions, etiological associations, staging, clinical treatment, and prognosis differ substantially and may have a significant clinical impact on the patient's treatment.