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Iwate Medical University Morioka 020-8505 Japan
In the article entitled "Sonography of Ankle Ganglia with Pathologic Correlation in 10 Pediatric and Adult Patients" [1], the authors pursued communication of ganglia with a joint cavity or tendon sheath. They showed communication of an ankle ganglion with the joint on sonography in three of the 10 patients, at surgery in four patients, and either sonographically or surgically in five patients. They also reported ganglion communication with the tendon sheath on sonography in one patient, at surgery in two patients, and either sonographically or surgically in three patients.
A ganglion, which is a common soft-tissue tumor, is defined as a benign cystic tumor with no synovial lining. Its communication with the joint is discussed only occasionally in the radiology literature or textbooks dealing with arthrography [2], but in the pathology or other literature this communication is either denied [3] or considered to be an exceptional or atypical feature [4, 5]. Communication with a tendon sheath is also considered unusual [4, 5].
The distinction between a ganglion and a synovial cyst is clearly defined on the basis of the presence or absence of synovial lining, but these terms are loosely applied because secondary changes in the capsule may make histologic differentiation difficult. We almost never call the cyst arising from the semimembranosus gastrocnemius bursa a ganglion, even when it has typical histologic features. Although there is some confusion in this subject, I think it is reasonable to designate communication with the synovium-lined spaces, such as joints and bursae, as a characteristic feature of a synovial cyst, not a ganglion, because surgical resection or biopsy is not always indicated.
The fibrous capsule shown in this article [1] is consistent with a ganglion, but the communication with synovium-lined space usually results in a finding of "synovial cyst." Although it may be an observation of only academic interest, communication of the ganglion with the joint is at least atypical or exceptional according to its original definition.
References
Akron Radiology Akron, OH 44309
We thank Dr. Ehara for his interest in our article [1]. Our results are correctly summarized, except for the fact that communication between the ganglion and tendon sheath was noted by sonography or surgery in two patients.
Resnick's textbook referenced by Ehara to support the "occasional" communication of a ganglion with the joint, states that "In the evaluation of wrist ganglia, contrast material injected directly into the swelling may fail to opacify the wrist, whereas contrast material injected into the wrist may reveal its communication with the soft tissue mass [2, 3]. This phenomenon of a `one-way valve' between the ganglion and articular cavity is similar to that noted with synovial cysts about any articulation" [4]. In the original article referenced by Resnick, Andren et al. injected the wrist joint in 59 patients with a ganglion cyst and showed filling of the ganglion in 37 patients and visualization of a duct from the joint (without filling of the ganglion) in nine additional patients [2]. Resnick's textbook also cites a case in which the ganglion communicates with a tendon sheath [5].
In our series, all cysts were diagnosed as ganglionic cysts by pathologic analysis, and a communication with a joint or tendon sheath was noted at surgery in six of the seven patients in which operative reports were available [1]. At surgery, Paivansalo et al. [6] noted a communication between the ganglion and joint or tendon sheath in 19 of 35 cases. Additional authors have noted that such a communication is not unusual [7, 8].
Enzinger and Weiss's pathology textbook, cited by Ehara, states, "There is no communication between the ganglion and the joint space" [9], but no references or data are cited to support this statement. Others have made similar statements, seemingly by definition rather than by data [10]. The terms "ganglion" and "synovial cyst" are often used loosely, and prior studies have not always obtained pathologic data to assess for a synovial lining. The term "paraarticular cyst" has also been used and may help avoid confusion and controversy [10].
Ehara believes that it is reasonable to designate cysts that communicate with the joint or bursa as synovial cysts, not ganglionic cysts, "because surgical resection or biopsy is not always indicated." However, we do not find this argument compelling because surgery or biopsy is not always indicated for ganglionic cysts. Once the diagnosis of a ganglion or a synovial cyst is established, surgery or intervention depends on clinical symptoms and patient preference [10].
We agree with Ehara and others who have noted that the distinction between ganglionic cysts and synovial cysts may be of only academic interest [10].
The distinction between ganglionic and synovial cysts should not obscure what is of prime importance: accurate diagnosis of a cyst, detection of associated joint pathology, and detection of any communication between the cyst and a joint or tendon sheath—because failure to resect such a communication can lead to recurrence [10,11,12].
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