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Presented by Dora Lam-Himlin, M.D. and prepared by Aatur Singhi, M.D., Ph.D.
Case 2: This 55 year-old woman developed a rapidly enlarging mass on her right ear.
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1. Question
Week 433: Case 2
This 55 year-old woman developed a rapidly enlarging mass on her right ear.images/1Alex/04262010case2image1.jpg
images/1Alex/04262010case2image2.jpgCorrect
Answer: Merkel cell carcinoma
Histology: The slide section shows mature cartilage of the pinna (outer ear) and a neoplasm with a dermal pattern of growth beneath a Grenz zone. The tumor is composed of sheets of monomorphic cells with large basophilic nuclei, opaque “glass-like” dispersed chromatin, and minimal cytoplasm with varying degrees of cohesiveness.
Discussion: Merkel cell carcinoma is a primary neuroendocrine tumor of the skin, composed of tumor cells with a “small round blue cell” appearance. In addition their characteristic nuclear features, Merkel cell carcinoma are usually immunoreactive for chromogranin, synaptophysin and CK20 (in a dot like pattern).
CK20, an intermediate filament protein with expression restricted to gastric and intestinal epithelium, urothelium, taste buds of the tongue, and Merkel cells, has been proposed as the cytokeratin marker best able to differentiate Merkel cell carcinoma from small-cell lung carcinoma and other cutaneous carcinomas. CK20 staining in Merkel cell carcinoma has a characteristic perinuclear punctate or dot-like pattern of positivity, while metastatic pulmonary small cell carcinoma, cutaneous squamous cell carcinoma, basal cell carcinoma and melanoma are negative for CK20.
Approximately 80% of Merkel cell carcinomas have been shown to be infected with Merkel Cell Virus (MCV), a member of the polyomavirus family. Merkel cell carcinoma is also associated with exposure to ultraviolet (UV) light and to ionizing radiation.
Reference(s):
– Feng, H., et al., Clonal integration of a polyomavirus in human Merkel cell carcinoma. Science. 2008 Feb 22;319(5866):1096-100. Epub 2008 Jan 17.
– McCardle, T.W., et al., Merkel cell carcinoma: pathologic findings and prognostic factors. Curr Probl Cancer. 2010 Jan-Feb;34(1):47-64.Incorrect
Answer: Merkel cell carcinoma
Histology: The slide section shows mature cartilage of the pinna (outer ear) and a neoplasm with a dermal pattern of growth beneath a Grenz zone. The tumor is composed of sheets of monomorphic cells with large basophilic nuclei, opaque “glass-like” dispersed chromatin, and minimal cytoplasm with varying degrees of cohesiveness.
Discussion: Merkel cell carcinoma is a primary neuroendocrine tumor of the skin, composed of tumor cells with a “small round blue cell” appearance. In addition their characteristic nuclear features, Merkel cell carcinoma are usually immunoreactive for chromogranin, synaptophysin and CK20 (in a dot like pattern).
CK20, an intermediate filament protein with expression restricted to gastric and intestinal epithelium, urothelium, taste buds of the tongue, and Merkel cells, has been proposed as the cytokeratin marker best able to differentiate Merkel cell carcinoma from small-cell lung carcinoma and other cutaneous carcinomas. CK20 staining in Merkel cell carcinoma has a characteristic perinuclear punctate or dot-like pattern of positivity, while metastatic pulmonary small cell carcinoma, cutaneous squamous cell carcinoma, basal cell carcinoma and melanoma are negative for CK20.
Approximately 80% of Merkel cell carcinomas have been shown to be infected with Merkel Cell Virus (MCV), a member of the polyomavirus family. Merkel cell carcinoma is also associated with exposure to ultraviolet (UV) light and to ionizing radiation.
Reference(s):
– Feng, H., et al., Clonal integration of a polyomavirus in human Merkel cell carcinoma. Science. 2008 Feb 22;319(5866):1096-100. Epub 2008 Jan 17.
– McCardle, T.W., et al., Merkel cell carcinoma: pathologic findings and prognostic factors. Curr Probl Cancer. 2010 Jan-Feb;34(1):47-64.
