[Muscular metastasis]

Neoplasia is quite rare in myology. For unknown reasons, muscular metastasis are rarely described in cancer.

Our work was a retrospective study with analysis of the medical literature and the presentation of one case of muscular metastasis revealed by a limitation of mouth opening in a 58-year-old Caucasian man (metastatic infiltration of the right pterygoid muscle secondary to a poorly differentiated adenocarcinoma of the lower third of the esophagus).

In addition to our case, we found 174 cases of cancer with muscular metastasis. Most of cases were observed in males (male/female ratio=2/1). The mean age at onset was 58.5 years (range: 13-89 years). The muscular metastasis were rarely found before the diagnosis of cancer (only in 37%), and usually appeared during disease progression, with other (extramuscular) metastases in 60% of cases. Prognosis was poor with less than 2.5% survival beyond 72 months. In most cases, muscular metastasis presented as a unique (78%), painful (61%) and palpable (63%) muscular mass, even if other asymptomatic muscular metastasis could be present. The mean localization of muscular metastasis was the lower limbs (46%), particularly in the proximal part (38% of all the muscular metastasis). The most frequent cancers were localized in lung, urinary tract, digestive tract and genital tract. When the muscular biopsy showed an "adenocarcinoma", in men the primitive cancers were localized in the digestive tract (35%), kidney (20%), and lung (18%) and in women, the genital tract and breast (23.5%). When the muscular biopsy showed a "squamous-cell carcinoma", in men the primitive cancers were localized in the lung (81%) and in women the cervix (64%).

These results highlight the importance of searching for muscular metastasis in patients with a focal, painful and palpable muscular mass. The muscular biopsy and immunohistochemical data can be helpful in identifying the primary cancer.