title: Metastatic signet-ring cell melanoma in a patient with an unknown primary tumor. Histologic, immunohistochemical, and ultrastructural findings.
abstract: Signet-ring cell melanoma is a rare morphologic variant of malignant melanoma. We describe a 27-year-old man with widespread cutaneous and internal metastases of an unknown primary tumor. One skin biopsy specimen and a fine-needle aspirate showed polygonal tumor cells consistent with the diagnosis of metastatic melanoma, but a second skin biopsy specimen revealed neoplastic cells with a signet-ring cell appearance. Both specimens, however, yielded identical immunohistochemical findings. Tumor cells were positive for vimentin and S-100 protein and reacted with the melanoma markers HMB-45 and NKI-C3. Ultrastructural studies revealed abundant intermediate filaments in the cytoplasm of the signet-ring cells. Based on these findings, a diagnosis of metastatic melanoma was made. In this report we describe the fourth case of metastatic signet-ring cell melanoma, and discuss how malignant melanoma may lead to metastases that have divergent morphologic appearances in the same patient.
authors.affiliation: Department of Dermatology, University of Munich, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Eckert
authors.forename: B
authors.initials: B
authors.lastname: Baricević
authors.forename: M
authors.initials: M
authors.lastname: Landthaler
authors.forename: U
authors.initials: U
authors.lastname: Schmid
mesh_terms: D000328:Adult; D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008545:Melanoma / Q000175:diagnosis / Q000473:pathology / Q000556:secondary* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009382:Neoplasms, Unknown Primary / Q000175:diagnosis* / Q000473:pathology / Q000648:ultrastructure; D009418:S100 Proteins / Q000032:analysis*; D012867:Skin / Q000473:pathology* / Q000648:ultrastructure; D012878:Skin Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000556:secondary* / Q000648:ultrastructure; D014746:Vimentin / Q000032:analysis*
chemical_list: D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor; D009418:S100 Proteins; D014746:Vimentin