Merkel cell carcinoma (MCC) is an aggressive neuroendocrine tumor of the skin that is associated with a high incidence of recurrence and metastasis. The thera peutic arsenal for this malignancy is limited and once it ...Merkel cell carcinoma (MCC) is an aggressive neuroendocrine tumor of the skin that is associated with a high incidence of recurrence and metastasis. The thera peutic arsenal for this malignancy is limited and once it spreads, there is no e ffective treatment, c-kit expression has been demonstrated previously in primar y MCCs thus raising the possibility of treating MCCs with imatinib mesylate, the tyrosine kinase inhibitor that has shown promise in the management of c-kit ex pressing tumors. In this study we examine 25 additional primary MCCs and also 6 of their lymph node metastases. Formalin-fixed, paraffin-embedded tissues were stained immunohistochemically with an antibody directed against the KIT recepto r. Percentage and intensity of staining were analyzed semiquantitatively using a three-tiered system. Twenty-one of the 25 (84%) primary tumors stained posit ively for KIT, of which 14 (67%) showed widespread positivity. Five of the 6 ly mph nodes (83%) were similarly positive. High mitotic rate and vascular invasio n in the primary tumors tended to be associated with prominent staining in the l ymph node metastases. No association was found between c-kit expression and out come. We confirm that the majority of primary MCCs express c-kit and further fi nd that metastases are positive for the KIT receptor as well. Thus, c-kit expre ssion may be an early event in the transformation of MCC, but not a marker for t umor progression.展开更多
文摘Merkel cell carcinoma (MCC) is an aggressive neuroendocrine tumor of the skin that is associated with a high incidence of recurrence and metastasis. The thera peutic arsenal for this malignancy is limited and once it spreads, there is no e ffective treatment, c-kit expression has been demonstrated previously in primar y MCCs thus raising the possibility of treating MCCs with imatinib mesylate, the tyrosine kinase inhibitor that has shown promise in the management of c-kit ex pressing tumors. In this study we examine 25 additional primary MCCs and also 6 of their lymph node metastases. Formalin-fixed, paraffin-embedded tissues were stained immunohistochemically with an antibody directed against the KIT recepto r. Percentage and intensity of staining were analyzed semiquantitatively using a three-tiered system. Twenty-one of the 25 (84%) primary tumors stained posit ively for KIT, of which 14 (67%) showed widespread positivity. Five of the 6 ly mph nodes (83%) were similarly positive. High mitotic rate and vascular invasio n in the primary tumors tended to be associated with prominent staining in the l ymph node metastases. No association was found between c-kit expression and out come. We confirm that the majority of primary MCCs express c-kit and further fi nd that metastases are positive for the KIT receptor as well. Thus, c-kit expre ssion may be an early event in the transformation of MCC, but not a marker for t umor progression.
