Desmoplastic leiomyosarcoma;  Case reference number US-BN-2022-000118 is a literature case report, title as stated above, identified on 08-Feb-2022, and concerns an 81-year-old elderly male patient.  On an unspecified date, the patient was vaccinated with MVA BN (smallpox vaccine modified vaccinia Ankara-Bavarian Nordic (live-attenuated, non-replicating)) in the upper left arm, at an unknown dose or route of administration, for unknown indication.  On an unspecified date, an unknown amount of time after the vaccination, the patient was presented to the clinic with a two point one cm firm, skin-colored subcutaneous tumor on the left upper arm. It was reported that the lesions had been slowly enlarging for approximately 4 years. The differential diagnosis included sympastic leiomyoma, and a variety of desmoplastic spindle cell lesions such as desmoplastic melanoma, cutaneous spindle cell carcinoma, and desmoplastic leiomyosarcoma  On an unspecified date, an unknown amount of time after the vaccination, following laboratory tests were performed: a punch biopsy and immunohistochemical staining, which revealed positive spindle cells for desmin and caldesmon.; immunostain for p53 was strongly and unformly positive; histopathology results had poor circumscription, which caused symplastic leiomyosarcoma to become ruled out as a diagnosis; negative S-100 staining in combination with the positive immunoreaction to muscle markers (desmin and caldesmon) caused desmoplastic melanoma to become ruled out as a diagnosis; negative p63 and cytokeratin staining excluded cutaneous spinde cell carcinoma as a diagnosis and ultimately, clinicopathologic correlation favoured the diagnosis of desmoplastic leiomyosarcoma. Staged excisions were performed to eradicate the lesions.  The outcome of the event desmoplastic leiomyosarcoma was not provided.  The event 'desmoplastic leiomyosarcoma' was assessed as serious due to the seriousness criteria of medical significance. The reporter did not provide seriousness and causality assessment for the event.  No further information was provided.; Reporter's Comments: An 81-year-old elderly male patient experienced a serious event of desmoplastic leiomyosarcoma (medically significant), unknown time after vaccination with MVA BN smallpox vaccine (modified vaccinia Ankara-Bavarian Nordic (live attenuated, non replicating)). Time to onset was not reported. Leiomyosarcoma is unexpected for MVA BN smallpox vaccine (modified vaccinia Ankara-Bavarian Nordic (live attenuated, non replicating)). Concomitantly used medications and patient's medical history were not reported. Leiomyosarcoma of the skin and subcutaneous tissue is a rare soft tissue malignant neoplasm. Time to onset was not reported. Patient's age confounds causality assessment. At this point with limited information provided causality is assessed as not related to MVA BN vaccine.; Sender's Comments: An 81-year-old elderly male patient experienced a serious adverse event of desmoplastic leiomyosarcoma (medically significant), after vaccination with MVA BN smallpox vaccine (modified vaccinia Ankara-Bavarian Nordic (live attenuated, non-replicating)). Time to the event's onset was not reported. Leiomyosarcoma is unexpected for MVA BN smallpox vaccine (modified vaccinia Ankara-Bavarian Nordic (live attenuated, non-replicating)). Concomitantly used medications, other vaccines administered and patient's medical history were not reported. Leiomyosarcoma of the skin and subcutaneous tissue is a rare soft tissue malignant neoplasm. Time to onset was not reported. Patient's age confounds causality assessment. Limited data is available on use of MVA BN in elderly population. At this point, with limited information provided causality is assessed as not related to MVA BN vaccine.