Pathologic Findings in Benign Pulmonary Histoplasmosis

Preliminary Report—Part II

¹ Director of Research, Pathology and Allied Sciences.
² Consulting Pathologist, Pathology Department of St. John's Hospital and Springfield Baptist Hospital, Springfield, Mo.
³ Histological Technician, Pathology Department of St. John's Hospital and Springfield Baptist Hospital, Springfield, Mo.

A preliminary report has been made on the pathologic findings of proved histoplasmosis in 21 circumscribed lesions and sixteen clinically active lesions. In addition, there were three doubtful cases in each group that were thought to be histoplasmosis, but in which no typical parasites could be found.

There were 24 more specimens examined in which histoplasmosis was not found. These served as good controls because they included principally tuberculosis, in which acid-fast bacilli were found and three cases of bronchogenic carcinoma. They were included because of the close similarity in clinical, x-ray or other findings to histoplasmosis.

There were four clinically active cases with both acid-fast bacilli and H. capsulatum.

In addition, three cases of known sarcoidosis as well as many controls of other diseases were stained and examined, but parasites were not found.

There were two series of cases, one including apparently inactive disease of so-called "coin" lesions and the other consisting of clinically active disease.

The pathologic findings were as follows: Group one, centrifugally formed spherical lesions; Group two, encapsulated infiltrates; Group three, caseous nodular lesions resembling caseous tubercles from 1 to 15 millimeters in diameter and fibrocaseous calcific and calcific-ossified lesions; the fourth group was chronic pneumonitis which is thought to be divided into several phases of age development from the histiocytic inltration and early organizing fibrinous pneumonia with histiocytes, to the late granulomatous-type of lesion that simulates sarcoidosis; Group five were the ulcerative types which are divided into caseo-ulcerative (an advanced stage of the caseo-nodular) and the fibroid type of lesions, which ranged from thin-walled, cystic, moderately thick-walled to thick fibrous-walled cavities; the sixth group was pure bronchiectasis that cannot be distinguished in appearance from any other bronchiectasis, but which was found to be a result of infection by H. capsulatum; Group seven was the pleuritic-type which is due to invasion of the pleura by H. capsulatum; an eighth group was a mixture of two or more of the others.

In preparing to make the examinations on this material, an exhaustive study was made of many types of artefacts which were removed or identified by special stains wherever possible.

The stain found best for staining yeast bodies was the Gomori methenamine silver (G.M.S) stain as adapted to the identification of yeast by Grocott.

Of the 16 definitely positive active cases, 14 were cultured and/or inoculated into mice, but only seven were found positive.

The findings were confirmed where possible by the use of the polariscope, as recommended by Potenza and Feo. While not diagnostic it does show the presence of a polarizing substance, probably a polysaccharide.

A theory was advanced for the possible evolution of the parasites in the body from the phagocytized cells in the macrophages to a quiescent spore-like form in the fibroid tissue and later a re-awakening of these spore-like forms (endospores) into active yeast cells at a time varying from months and years to decades. A further elaboration of these possibilities will be carried out in a subsequent work where more discussion will be possible.