FILARIASIS 237 
Filarial Cyst. On the Upper Congo, near Stanleyville, through the courtesy 
of Dr. Chesterman, we observed in the hospital a case (No. 560) with a small 
tumor, about 5 cm. in diameter, situated on the right arm, about 6 em. above 
the elbow and lying along the inner aspect of the biceps muscles in the sub- 
cutaneous tissue. It was freely movable, soft and cyst-like. The examina- 
tion of the peripheral blood from the ear showed long, thin, filarial embryos 
with a sheath which from the examination of stained preparations suggested 
Microfilariae loa. Microscopical preparations made from the inner wall of 
the tumor showed a number of red blood corpuscles and a few similar micro- 
filariae. The tumor was removed by Dr. Chesterman and was kindly turned 
over to us for examination. It was fixed in formalin and proved to be a thin- 
walled cyst containing straw-colored fluid and a single parasite about 5 cm. 
in length lying free in the fluid. The worm was later identified as an adult 
female Loa loa. This is apparently the first reported instance of the formation 
of a cystic tumor by this parasite. A section through the wall of the cyst is 
illustrated in No. 175. Neither Sticker, Schuffner, and Swellengrebel? or 
Filleborn ? in his monograph on Filaria of Man, refer to such a lesion produced 
by Loa loa. 
The adult Loa loa have been found in connective tissue in many parts of 
the body, particularly in the subcutaneous tissue, under the muscular aponeu- 
rosis of the muscles of the extensor surfaces of the arms, for example. Stephens 
and Yorke refer especially to such location, and also mention the occurrence 
of the parasites on the surface of the organs in the mesentery, under the parie- 
tal peritoneum and pericardium, encysted in the tunica vaginalis, and heart 
muscle, in the anterior chamber of the eye, under the ocular and palpebral 
conjunctivae, over the bridge of the nose and in the frenum linguae. According 
to these authors, Ziemann has attributed inflammatory swellings, both in mus- 
cular and connective tissue, which may suppurate, to infection with Loa loa. 
There is no evidence of inflammatory change in the cyst wall of our tumor 
and there is no cellular infiltration of the surrounding connective tissue. The 
cyst probably represents a dilatation of a gland-like cavity. It appears as 
though the fibers of the surrounding tissue had gradually been pressed apart 
by the movements of the parasite and the slowly accumulating fluid. In the 
surrounding tissues a few millimeters outside the cyst wall, there are wavy 
bands of areolar connective tissue with a few red blood cells and leucocytes 
lying within the interstices. Lying upon the right side of the cyst wall is a 
protrusion of the tissue composed of unstriped muscle fibers whose origin is not 
entirely clear. It seems probable that the parasite originally developed to 
its adult size within a lymphatic vessel whose walls gradually became occluded. 
It, however, is impossible from the structure of the cyst wall to decide whether 
the tumor was formed originally about a lymphatic vessel. 
In connection with the production of this filarial cyst, it is of some interest 
1 Sticker, Schuffner, and Swellengrebel: Mense’s ‘‘ Handbuch der Tropenkrankheiten”’ (1929), V, 
309. 
2 Fit leborn: ‘‘Handbuch der Pathogenen Mikroorganismen”’ (1929), VI, 1171. 
