Diagnosis of thoracic endometriosis with immunohistochemistry

Pathological and immunohistochemical features of thoracic endometriosis are not well understood. In the present study, we retrospectively analyzed the clinical and pathological diagnostic characteristics of 55 female pneumothorax cases.

This study was a retrospective observation of 55 women aged from 8 to 62 years old who underwent surgery for pneumothorax from November 2001 through January 2018. Immunohistochemistry for estrogen receptor (ER), progesterone receptor (PR), and CD10 was performed for all cases. As controls, we analyzed resected specimens of spontaneous pneumothorax in men who received surgery.

Of 55 cases, endometrial stroma and glands by Hematoxylin-Eosin (HE) stain was found in only one case. Thirty-seven cases (67.3%) were ER- and PR-positive in stromal bland spindle cells of the lung. The remaining 18 cases (32.7%) were ER-, PR-, and CD10-negative. The ER- and PR-positive specimens could be further classified according to 2 staining patterns: 'scattered pattern' and 'aggregated pattern'. Thirty-three cases (60.0%) were scattered and four cases (7.3%) were aggregated pattern. Only the aggregated pattern specimens exhibited positive staining for CD10. As the scattered pattern was also found in men, we only diagnosed the aggregated pattern cases as endometriosis.

A diagnosis of thoracic endometriosis is simple when both endometrial stroma and gland are present. In cases of endometriosis with stroma only, a further classification of "aggregated pattern", in which immunohistochemistry is ER-, PR- and CD10-positive might be necessary for diagnosis.