Establishment and characterization of a human cell line, HS-MM, derived from a case of clear cell sarcoma

The characteristics of a new human clear cell sarcoma (CCSa) cell line, HS-MM, established from the pleural effusion in a 39-year-old man with lung metastasis, have been morphologically studied in vitro and in vivo. HS-MM cells growing on a cover-slip were round or spindle in shape with round nuclei containing extremely prominent nucleoli. Heterotransplantation of the cells into nude mice was easily succeeded following tumor development. Light microscopically, HS-MM cells, both in vitro and in vivo, were positive for anti-S-100 protein and anti-melanoma specific antibodies with immunostain, but no melanin pigment was detected in them. Ultrastructurally, the cells had round euchromatin-rich nuclei with large nucleoli revealing conspicuous nucleolonema, and contained a few mitochondria, rough endoplasmic reticulum and lysosomal dense bodies, besides a large amount of glycogen, but no melanosome in their cytoplasm. HS-MM cells retained and fully expressed morphologically unique characteristics as a CCSa, compatible with amelanotic type of malignant melanoma also. This cell line, HS-MM, therefore, proves to be extremely useful for clinicopathological studies on a CCSa.