Melanoma cell heterogeneity. A study of two monoclonal antibodies compared with s-100 protein in paraffin sections

Abstract

Fifty-six formalin, Bouin's, and Carnoy's fixed, paraffin-embedded malignant melanomas (21 primary, 35 secondary), were studied by avidin-biotin complex immunohistochemistry using monoclonal antibodies (MoAb) HMB-45 and B1.1, comparing reactivity with polyclonal anti-S-100 protein. B1.1 (anti-CEA MoAb) was expressed in a minor percentage of cells of the invasive component of some primary melanomas, and weak to moderately in scattered metastic melanoma cells. MoAb HMB-45 prepared against melanocytic tumors reacted with over 90% of all tumors studied, being weakly reactive in one, and nonreactive in four metastases. This antibody stained some primary melanomas and their dysplastic nevus components in a heterogeneous manner, but was largely nonreactive in deep dermal nevus cells that were in association with invasive melanoma, enabling recognition of the deepest penetration of melanoma cells in the dermal nevus component. MoAb HMB-45 appears specific for melanoma cells, with no cross-reactivity with nonnevomelanocytic malignant tumors (unlike polyclonal anti-S-100 protein). MoAb HMB-45 is more sensitive in detecting malignant melanoma cell heterogeneity than anti-S-100 protein.

Macrophage‐rich epithelioid angiosarcoma mimicking malignant melanoma

“…2A). The epithelioid cells showed both nuclear and cytoplasmic staining with S‐100 protein, with enhanced nuclear staining present, similar to that observed in nevi and melanoma, 2 suggestive of a malignant melanoma and initially corroborating the clinical impression.…”

Mohs Micrographic Excision of Melanoma Using Immunostains

“…The sensitivity of HMB‐45 for melanoma on paraffin‐embedded sections has been reported to be 86–97%. 27–34 HMB‐45 staining is often negative in spindle cell melanomas, including desmoplastic and neurotropic melanomas, although newer antigen retrieval techniques have been reported to increase sensitivity to 75% of spindle cell melanomas. 35,36 Up to 75% of tumors are positive diffusely, especially areas of epithelioid cells; 27,30,31,33 however, staining of melanomas with HMB‐45 may be focal and patchy, and intensity of staining individual cells varies from weak to strong.…”

Malignant melanoma in transgenic mice.

“…4). The eye and skin tumors are histopathologically similar to corresponding human melanomas, with a preponderance of epithelioid and spindle cells, frequent S-100 and HMB-45 reactivity (16), and premelanosomes or melanosomes (Fig. 5).…”