Merkel cell tumour with leiomyosarcomatous differentiation

Abstract

Aims: To report and confirm the identity of tumour cells showing leiomyosarcomatous differentiation in a regional lymph node containing metastatic Merkel cell tumour. Methods and results A 79‐year‐old woman was found to have metastatic Merkel cell tumour within an axillary lymph node 4 months after excision of the primary tumour from the forearm. The lymph node was effaced by tumour identical to that of the primary tumour but there was an additional focus of loose spindle cells. Immunocytochemical staining showed the coexpression of cytokeratin 20, neurofilament and desmin in these sarcomatous cells. Conclusion This, to the best of our knowledge, is the first report of Merkel cell carcinoma showing sarcomatous differentiation, and adds to the expanding morphological spectrum of malignant biphasic tumours.

Clinicopathological and immunohistochemical analysis of 20 cases of Merkel cell carcinoma in search of prognostic markers

“…MCC with BD, AK and BCC 31 are also present in some cases. Furthermore, exceedingly rare patterns of differentiation include rhabdomyosarcomatous, 32 leiomyosarcomatous, 33 lymphoepithelioma‐like 18,34 and atypical fibroxanthoma‐like 35 …”

Which Are the Cells of Origin in Merkel Cell Carcinoma?

“…In detail, MCCs associated with diverse differentiation patterns have been described: squamous [52], squamous and sarcomatous [53], melanocytic [54], eccrine [55], leiomyosarcomatous [56], rhabdomyoblastic [57], and fibrosarcomatous [58] differentiation. Although there is a certain immunophenotypical diversity in MCs themselves [41], the multitude of differentiation patterns in MCC rather points to stem or early progenitor cells as cells-of-origin.…”

Merkel Cells, Normal and Neoplastic: An Update

“…Focal squamous differentiation is not infrequent [3] (Figure 6). Very rarely, atypical fibroxanthomalike and leiomyosarcomatous differentiation have been observed [26,27].…”