Craig Paul J, Calonje Jaime E, Harries Mark, Stefanato Catherine M
Department of Dermatopathology, St John's Institute of Dermatology, Guys and St Thomas' NHS Foundation Trust, London, UK.
J Cutan Pathol. 2009 Jun;36(6):706-10. doi: 10.1111/j.1600-0560.2008.01115.x.
Chronic lymphocytic leukaemia (CLL) shows cutaneous involvement in 2% of cases. Merkel cell carcinoma (MCC) is a rare primary cutaneous epithelial neoplasm most commonly found in sun-exposed sites in elderly male Caucasians. A 66-year-old man presented with a 2-month history of a purple painless 2 cm tumor on the scalp. Excision biopsy revealed an incompletely excised MCC, and at the periphery of the MCC, a lymphocytic infiltrate interpreted as reactive. A re-excision biopsy showed residual MCC as well as dense aggregates of small lymphocytes within and surrounding the MCC. Immunohistochemistry showed characteristic dot-like cytoplasmic positivity for cytokeratin 20 in the MCC; the lymphocytic infiltrate was positive for CD5, CD20 and CD23, diagnostic of CLL. Subsequent staging revealed widespread lymphadenopathy, and lymph node biopsy showed CLL. Histologically, CLL and MCC are 'round blue cell tumors' and are therefore in the differential diagnoses of each other. Whenever there is a more prominent than expected infiltrate of small lymphocytes surrounding a skin lesion in an elderly patient, immunohistochemistry to rule out CLL is advised. This case adds to the literature suggesting an increased incidence of CLL and other neoplasms in patients with MCC and vice versa.
慢性淋巴细胞白血病（CLL）在2%的病例中会出现皮肤受累。默克尔细胞癌（MCC）是一种罕见的原发性皮肤上皮性肿瘤，最常见于老年男性白种人的阳光暴露部位。一名66岁男性患者，头皮出现一个紫色无痛性2厘米肿瘤，病史2个月。切除活检显示为未完全切除的MCC，在MCC周边有淋巴细胞浸润，考虑为反应性浸润。再次切除活检显示仍有残留的MCC，以及MCC内部和周围有密集的小淋巴细胞聚集。免疫组化显示MCC中细胞角蛋白20呈特征性点状胞质阳性；淋巴细胞浸润对CD5、CD20和CD23呈阳性，诊断为CLL。随后的分期显示广泛的淋巴结病，淋巴结活检显示为CLL。从组织学上看，CLL和MCC都是“圆形蓝细胞瘤”，因此彼此在鉴别诊断中。在老年患者中，每当皮肤病变周围出现比预期更明显的小淋巴细胞浸润时，建议进行免疫组化以排除CLL。该病例补充了文献资料，提示MCC患者中CLL及其他肿瘤的发病率增加，反之亦然。
