Pleuro-pulmonary endometriosis and pulmonary ectopic deciduosis: a clinicopathologic and immunohistochemical study of 10 cases with emphasis on diagnostic pitfalls

The clinical and pathological features of nine cases of pleuro-pulmonary endometriosis and the first case of pulmonary ectopic deciduosis are presented. The patients were all women between the ages of 27 and 74 years (median, 36 years) who presented with symptoms of catamenial pleural pain, shortness of breath, hemoptysis, or radiographically detected lung masses. Clinically, six patients were multiparous, one patient had pelvic endometriosis, and four patients had undergone prior pelvic surgical procedures, including dilatation and curettage. Radiographically, eight patients had pulmonary infiltrates or nodules, and four patients had pneumothorax. Three cases involved the visceral pleura and one case the parietal pleura. The other six cases, including the single case of ectopic deciduosis, involved the lung parenchyma. Histologically, the single or multifocal lesions were well circumscribed or infiltrative, nodular, cystic, or nodulo-cystic, and showed the characteristic features of proliferative or secretory endometrium with numerous mullerian metaplastic changes. Mucin stains were negative in five cases of endometriosis and in the single case of ectopic deciduosis. Immunohistochemical studies were performed in these same six cases using antibodies to epithelial, mesenchymal, vascular, and neuroendocrine markers. The glandular epithelium was decorated with antibodies to pan-cytokeratin, CK7, BER-EP4, ER, and PR, whereas the stromal cells showed positive staining for vimentin, actin, smooth muscle actin, desmin, ER, and PR. Follow-up information obtained in seven patients showed all women without recurrences after 1 to 20 years. The current study highlights the importance of recognizing intrathoracic endometriosis and ectopic deciduosis and properly assessing small biopsy specimens to avoid a misdiagnosis of malignancy.