Thoracic Endometriosis

To the Editor:— In their interesting case report, "Thoracic Endometriosis With Recurrent Spontaneous Pneumothorax" (196:595, 1966), Drs. Kovarik and Toll note the apparent predilection of thoracic endometriosis for the right hemithorax. They point out that only one of the reported lesions was "in the left lung." I assume they refer to the patient reported by Dr. Jones and myself (New Eng J Med266:805, 1966) and would like to stress that the lesion was not in the pulmonary parenchyma but in the wall of a bronchus. The x-ray-film shadows seen in our patient disappeared between menses and doubtless represented blood. I fear this does not help in elucidating the mechanism for extragenital endometriosis, but keeping the difference in mind may help avoid confusion.