title: Merkel cell carcinosarcoma: Merkel cell carcinoma with embryonal rhabdomyosarcoma-like component.
abstract: Merkel cell carcinoma is an uncommon primary neuroendocrine neoplasm of the skin that may exhibit divergent differentiation. However, rhabdomyosarcomatous differentiation has only been rarely described and takes the form of isolated rhabdomyoblasts. We describe a case of cutaneous Merkel cell carcinoma with biphasic morphology imparted by discrete patches of embryonal rhabdomyosarcoma-like spindle cells alternating with islands of neuroendocrine small round cells, justifying a designation of "Merkel cell carcinosarcoma." The former component showed positive immunostaining for desmin and myogenin; and the later component, pan-cytokeratin, cytokeratin 20, synaptophysin, and chromogranin. The patient was an elderly man who presented with a temporal skin mass, and the biphasic morphology was evident in the recurrence and metastasis that developed 2 months after incomplete excision of the skin lesion.
authors.affiliation: Department of Pathology, Queen Elizabeth Hospital, Hong Kong SAR. lau_pak_lun@yahoo.com
authors.forename: Patrick Pak-Lun
authors.initials: PP
authors.lastname: Lau
authors.forename: S H
authors.initials: SH
authors.lastname: Ting
authors.forename: Y T
authors.initials: YT
authors.lastname: Ip
authors.forename: William Y W
authors.initials: WY
authors.lastname: Tsang
authors.forename: John K C
authors.initials: JK
authors.lastname: Chan
mesh_terms: D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D015266:Carcinoma, Merkel Cell / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D017809:Fatal Outcome; D006801:Humans; D008297:Male; D009364:Neoplasm Recurrence, Local; D009378:Neoplasms, Multiple Primary; D018233:Rhabdomyosarcoma, Embryonal / Q000378:metabolism / Q000473:pathology* / Q000601:surgery; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000601:surgery
chemical_list: D014408:Biomarkers, Tumor