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Pulmonary malacoplakia associated with Rhodococcus equi, an opportunistic Gram-positive coccobacillus, is unusual. Although this patient is the ninth reported to have pulmonary malacoplakia, he is only the third patient with the acquired immunodeficiency syndrome who has been reported to have pulmonary malacoplakia associated with R equi infection. The patient was a 49-year-old man infected with the human immunodeficiency virus who on initial examination was found to have cavitary pneumonia in the right upper lobe of the lung. Histologic examination of an open-lung biopsy specimen revealed sheets of foamy intraalveolar macrophages that contained coccobacillary organisms and some "targetlike" cytoplasmic inclusions. Electron-microscopic studies showed Michaelis-Gutmann bodies, some of which contained residual bacterial fragments. Cultures of the lung tissue, urine, and blood yielded growth of Gram-positive coccobacilli subsequently identified as R equi. In immunocompromised patients, the possibility of malacoplakia should be considered in the differential diagnosis of diffuse pulmonary infiltrate composed of foamy intraalveolar macrophages.

The authors report the histologic and immunohistochemical findings of two cases of diffuse embryoma of the testis, a distinct form of mixed-germ-cell tumor characterized by diffuse, orderly arrangement of embryonal carcinoma (EC) and yolk sac tumor (YST) with scattered trophoblastic components. The patients were 37 and 38 years old when they presented with a right testicular tumor, which was confined to the testis (stage I) in both cases. Histologically, the tumor was composed predominantly of intimately intermingled EC and YST components in almost equal proportion. The tumor cells were arranged in necklacelike fashion; the EC cells formed glandular structures rimmed by a single cell layer of YST cells. The YST component was highlighted by positive staining for alpha-fetoprotein and strong staining for cytokeratin, whereas the EC component was positive for Ki-1 (BerH2, CD30) antigen, was negative for alpha-fetoprotein, and stained more weakly for cytokeratin. The randomly distributed few trophoblastic elements stained for human chorionic gonadotropin. The patients are alive with no evidence of disease, 11 years and 9 months after surgery, respectively. This newly described but distinct variant of mixed-germ-cell tumor should be differentiated from polyembryoma, which is composed of multiple discrete embryoid bodies.