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Occurrence of proliferative myositis after COVID-19 vaccination: A case report
Ramin Ebrahimi1, Amir Sajjad Mounesi Sohi2, Mohammad Saeid Khonji3
1Department of Radiology, Firoozgar Hospital, Iran University of Medical Sciences, Tehran, Iran.
Abstract:
Proliferative myositis (PM) is a benign intramuscular tumor that might mimic a malignant one due to its unusual pseudosarcomatous inflammatory nature. In this report, we describe a patient who developed PM after vaccination with Sinopharm coronavirus disease (COVID-19) vaccine. A 73 years old man was admitted due to rapidly-growing painful mass in his left thigh from a few days ago, curtailing his walking. He received a recent COVID-19 vaccination (Sinopharm COVID-19 vaccine) about 5 days before the beginning of symptoms. No history of trauma was present. On physical exam, a round firm mass was found in lateral side of mid portion of left thigh within the muscle with tenderness on palpation. An oval-shaped well-defined intramuscular mass measured 15 × 41 mm was noted in vastus lateralis muscle in ultrasonography. Left thigh magnetic resonance imaging (MRI) showed a well-defined intramuscular mass with a definite margin of 19 × 39 mm. Finally, ultrasound (US)-guided core needle biopsy showed muscular tissue with a loose mass composed of plump fibroblasts and myofibroblasts and large ganglion-like cell with abundant amphophilic to basophilic cytoplasm, vesicular nuclei and prominent nucleoli. Pathology report showed a very rare case identified as proliferative myositis. It should be noted that we cannot make a direct link between these 2 events. PM is an extremely rare entity; however, its relation with COVID-19 vaccination might be a coincidence.
Insights
Proliferative myositis, a rare benign tumor, presented as a rapidly growing thigh mass shortly after Sinopharm COVID-19 vaccination. While a direct link is unconfirmed, this case highlights a potential, though likely coincidental, association.
Area of Science:
- Oncology
- Pathology
- Vaccinology
Background:
- Proliferative myositis (PM) is a rare, benign intramuscular tumor known for its pseudosarcomatous inflammatory appearance.
- Distinguishing PM from malignant tumors can be challenging due to its aggressive presentation.
Observation:
- A 73-year-old male developed a rapidly growing, painful left thigh mass five days post-Sinopharm COVID-19 vaccination.
- Physical examination revealed a tender, firm, intramuscular mass in the vastus lateralis muscle.
- Imaging (ultrasound and MRI) confirmed a well-defined intramuscular mass measuring approximately 19x39 mm.
Findings:
- Ultrasound-guided core needle biopsy demonstrated a mass composed of fibroblasts, myofibroblasts, and large ganglion-like cells.
- Histopathological analysis confirmed the diagnosis of proliferative myositis.
- The patient had no history of trauma preceding the mass development.
Implications:
- This case presents a rare instance of proliferative myositis occurring temporally after COVID-19 vaccination.
- While a causal link cannot be established, the temporal association warrants further investigation into potential vaccine-related inflammatory responses.
- The findings underscore the importance of considering rare diagnoses in patients presenting with new masses post-vaccination, even if the association is likely coincidental.
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