Intramuscular Cysts at the Proximal Calf: Two Case Reports and a Systematic Review of Literature

Abstract

Intramuscular cysts at the proximal calf are rare; however, their etiology is diverse, making accurate diagnosis and treatment difficult. To our knowledge, there are no previous publications in literature about intramuscular cysts at the proximal calf, arising from different origins. This article describes two rare cases with intramuscular cysts. Case 1 was diagnosed as an intramuscular ganglion cyst arising from the proximal gastrocnemius medialis muscle, and arthroscopic examination as well as open cyst excision was performed. Case 2 was another type, which has never been reported in the literature. It was diagnosed as diffuse pigmented villonodular synovitis (PVNS), with the intramuscular cyst arising from PVNS, and only arthroscopic synovectomy was performed. The diagnoses for these cases were confirmed by histopathology. In addition, we have summarized intramuscular cysts at the proximal calf by a systematic literature review and divided them into five types based on their origin. The five types are, intramuscular cysts arising from the muscular tissue, knee joint, proximal tibiofibular joint, the neurilemma and PVNS. The treatment of intramuscular cysts varies based on their origin; hence, it is important to identify the origin.

Proximal Tibiofibular Joint Ganglion Cyst: A Rare Cause of Calf Pain

“…Intramuscular ganglion cysts arising from the PTF joint at the proximal calf are rare; nevertheless, their etiology is diverse, making accurate diagnosis and treatment really difficult [1]. The most commonly accepted theory is that they generate from secondary myxoid degeneration of connective tissue, which is associated with joint capsules and sheaths of tendons [3].…”

“…Additionally, it is well known that over 50% of cysts of the PTF joint are associated with peroneal nerve palsy, from the compression of the common peroneal nerve in the peroneal canal [4,5]. MRI scan is the gold standard for precise diagnosis [6], while aspiration is not recommended for ganglion cysts as they have a high chance of recurrence [1]. Differential diagnosis includes tendon tear, Baker's cyst, bursitis, tenosynovitis abscess, myxoma, nerve sheath tumor, vascular lesions, lipomas, and synovial sarcoma [7].…”

“…To our knowledge, an intramuscular ganglion cyst to the lateral gastrocnemius muscle is a very rare entity with only two cases in the literature [7,8], while an intramuscular ganglion cyst to the lateral gastrocnemius arising from the PTF joint with a huge pedicle has never been reported in the literature. PTF joint intramuscular ganglion cysts are commonly presented in the anterolateral aspect [1] of the knee and frequently are associated with peroneal nerve palsy [1,9]. The most important differential diagnosis in cases with cysts to the posterior aspect of the proximal calf includes Baker's cyst, although clinicians should be aware that Baker's cyst usually arises from the semimembranosus-gastrocnemius bursa.…”

“…Intramuscular cysts of the proximal calf are very rare, and the causes of these cysts are varied. The five types of these cysts are the following: cysts from the knee joint, intramuscular cysts arising from the muscular tissue, neurilemma, cysts from the proximal tibiofibular (PTF) joint, and pigmented villonodular synovitis (PVNS) [1]. Ganglion cyst (GC) of the PTF joint is a very rare entity with an estimated prevalence of just 0.76% [2].…”