The Roentgen Treatment of Myxomatous Cutaneous Cysts

THE fact that myxomatous cutaneous cysts are especially amenable to roentgen therapy has not received adequate emphasis in radiologic literature. Previously, these were included with “synovial lesions of the skin.” In 1937, however, Gross (1) called attention to their true pathologic nature as a myxomatous degeneration of the corium, the strong tendency to recurrence despite wide surgical excision, and the curative effect of irradiation. This subject may concern radiologists frequently enough that they should recognize the lesions and the necessity for the application of mild caustic irradiation. We have found the exposures recommended to be inadequate and suggest 1,400 to 1,600 r, measured in air, of low-voltage roentgen rays at one sitting as satisfactory treatment. Seven cases are included to illustrate characteristic findings and favorable results following adequate radiotherapy. Etiology The cause of myxomatous cutaneous cysts is unknown. Several theories regard them as due to localized repeated trauma or to vascular changes resulting in local collagenous degeneration, as connective-tissue tumors with necrosis, a variant of Heberden's nodes of osteoarthritis, or development from an out-pocketing of a synovial membrane. There is no evidence to indicate an inflammatory origin. Incidence These cysts are infrequent since, even in an active dermatologic service, only seven examples were found within three years. They occurred predominantly in women. The usual age group is that from the fourth to the sixth decade, although instances in patients as young as twenty-six years of age have been reported. All patients we studied were of the white race and, with one exception, were over fifty years of age. The occupation of the majority of the patients necessitated considerable use of the hands. Clinical Findings The usual appearance is that of a globular, raised, smooth cyst which can be trans-illuminated and is covered by thin skin of normal color. It is commonly situated at one side of the dorsal aspect of a distal phalanx. When it is punctured, a thick, lemon-colored syrupy fluid can be expressed. If the cyst impinges on the root matrix, grooving of the nail results. The average diameter at the base is 5 mm. with an average height of 3 mm. The cysts are never reducible by forceful pressure in contradistinction to true synovial cysts or ganglia. Another differential point is that, since the myxomatous cyst is an integral part of the corium, the skin cannot be moved over it. In unusual cases, the lesions may be extremely thin-walled so as to resemble vesicles; or they may be very rough, resembling verrucae (Fig. 1). Occasionally, the lesions are centrally umbilicated (Fig. 2). Atypically, they may also be encountered on parts of the fingers, toes, hands, or feet other than the distal phalanges. If recently traumatized or if secondarily infected, the base of the cyst may be surrounded by a small zone of inflammation.