PMC5548690_01
A: T2-weighted MRI showed an abnormal low-signal mass lesion toward the back from the head side of the bladder. B: This lesion showed an internal heterogeneous contrast effect on T1 with gadolinium enhancement. C, D, E: Short tau inverted recovery imaging on muscle MRI revealed high signal lesions on the left side of the triceps (C; axial view, E; coronal view) and latissimus dorsi (E; axial view) muscles.
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Abdominal ultrasound showed solid echo findings on the posterolateral side of the bladder, and T2-weighted images on MRI showed an abnormal low signal mass lesion with an internally heterogeneous contrast effect upon T1 gadolinium enhancement, which suggested metastasis of uterine cancer (Fig. 1A and B). Short tau inverted recovery images on muscle MRI revealed high-signal intensity lesions on the left side of the latissimus dorsi and triceps muscles (Fig. 1C-E).
A, D: A Hematoxylin and Eosin (H&E) staining section of the left biceps shows various sizes of muscle fibers, with necrotic and regenerating fibers (A). B, C, E: Enzyme immunostaining revealed an increase in the expression of CD8-positive lymphocytes (B), MHC-I (C), and macrophages (E). F: Enzyme immunostaining revealed anti-3-hydroxy-3-methylglutary-coenzyme A reductase antibody-positive fibers (arrow) colocalized with regenerating muscle fibers in an H&E staining section [D (arrow)].
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Hematoxylin and Eosin staining sections showed muscle fibers of various sizes accompanied by necrotic and regenerating fibers, and inflammatory cell infiltration (Fig. 2A and D). Muscle fiber immunostaining also showed the findings of myositis, including the co-localization of CD8 immunoreactivity (Fig. 2B) and major histocompatibility complex 1 (MHC-1) (Fig. 2C). On the other hand, the infiltration of macrophages (Fig. 2E) and a positive immunoreaction for HMGCR (Fig. 2F) colocalized with regenerating muscle fibers in H&E staining sections (Fig. 2D [arrow]) suggested IMNM.
A high serum level of CK was detected at 3 years after the operation while the patient was receiving chemotherapy (tegafur-uracil). Her high serum level of CK continued even after the cessation of tegafur-uracil and motor weakness appeared. After admission, her high serum level of CK spontaneously declined at rest, but her motor weakness did not improve, and the CK value remained in the range of 4,000-6,000 mg/dL.Oral prednisolone was started at a dose of 40 mg/day. Her serum level of CK was reduced and her clinical symptoms gradually improved during steroid therapy. No relapse occurred during the tapering of prednisolone.
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The clinical course is shown in Fig. 3.