Track: Clinical Studies

Topic: Melanocytic Neoplasms

Abstract:

Both exfoliative and aspiration cytology are frequently employed in the diagnosis of metastatic melanoma. The utility of preferentially expressed antigen in melanoma (PRAME) as a marker for primary and metastatic melanoma has recently been established. In cytology, there is often limited or no diagnostic material available in the cell block for ancillary immunocytochemistry (ICC) to confirm metastatic melanoma. In this setting, one option to obtain ICC is to overstain a previously Papanicolaou (Pap) stained slide containing lesional cells with the desired ICC stain. To our knowledge, no studies have analyzed the performance of PRAME ICC for melanoma diagnosis using previously Pap-stained slides. Consequently, our objective was to assess the effectiveness of PRAME ICC as a marker for metastatic melanoma in Pap-stained cytologic preparations. Fourteen cases of metastatic melanoma diagnosed via exfoliative or aspiration cytology at our institution were retrospectively identified, and one Pap-stained slide from each case was overstained with PRAME ICC. Moderate-strong nuclear staining in 75% of tumor cells was used as criteria for positivity, but focal or weak nuclear positivity was also noted. PRAME was positive in 7/14 (50%) of cases, however, 3/7 (43%) of the negative cases showed weak or focal positivity. The results indicate that PRAME ICC performed on previously pap-stained slides with lesional cells may be useful as a specific marker in diagnosing metastatic melanoma when there is scant or no diagnostic material present in the cell block. The sensitivity appears to be higher if less strict criteria are used in interpretation.

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Kelly Hall, MD