The diagnostic utility of Merkel cell polyomavirus immunohistochemistry in a fine needle aspirate of metastatic Merkel cell carcinoma of unknown primary to the pancreas

Merkel cell carcinoma (MCC) is an aggressive skin tumor with a high tendency for metastases. We report a case of MCC initially presenting as axillary and pancreatic metastases. A 33‐year‐old HIV‐positive Hispanic male presented with a history of a rapidly growing axillary mass. A needle core biopsy demonstrated an epithelioid neoplasm composed of small to medium‐sized cells with high nuclear‐cytoplasmic ratio, nuclear molding, and frequent mitotic figures. A subsequent PET scan revealed a 1.5 cm FDG avid mass in the pancreas. Endoscopic ultrasound‐guided FNA of the pancreatic mass showed neoplastic cells with similar morphology to those of the axillary mass. The tumor cells were positive with pancytokeratin AE1/AE3, CK20, CD56, synatophysin, chromogranin, and Merkel cell polyomavirus (MCPyV). This case of MCC most likely originated from a resolved primary skin lesion drained by the involved axillary lymph node with subsequent metastases to the pancreas and distant lymph nodes.     

Pulmonary gangliocytic paraganglioma: a case report and review of the literature

Gangliocytic paraganglioma (GP) is a rare histologic type of neuroendocrine tumors. We report a case of pulmonary GP in a 29-year-old male presenting with an asymptomatic endobronchial nodule. Grossly, the tumor showed a 4.0x3.8x3.5 cm well-defined nodule with yellowish cut surface. Microscopically, the tumor was composed of three distinct cellular types: epithelioid cells, ganglion-like cells and spindle cells. Meanwhile, transitional cells, having morphologic features between ganglion-like and epithelioid cells, were also presented. The epithelioid cells arranged in various morphologic architectures, including Zellballen, papillary, cystic and microcystic pattern. The epithelioid cells were positive for AE1/AE3, CAM 5.2, chromogranin A and synaptophysin. Ganglion-like cells showed immunoreactivity for chromogranin A and synaptophysin. A few ganglion-like cells were also positive for AE1/AE3 and/or CAM 5.2. The spindle cells were positive for S-100 protein and neurofilament. The transitional cells showed a similar immunohistochemical profile to the epithelioid cells. The authors believe stem cell theory is a reasonable explanation for the origin of GP. GP probably originate from some kind of mucosa associated stem cell which can differentiate into diverse cellular lineages.     

Antigen expression associated with lymph node metastasis in gastric adenocarcinomas

A total of 100 gastric adenocarcinomas, comprising 50 cases with lymph node metastasis and 50 cases without lymph node metastasis, were examined for immunohistochemical reactivity with the monoclonal antibody to urokinase-type plasminogen activator (u-PA), Le^x related 4C9 antigen, Jun, or to nucleobindin (Nuc). In tumors with lymph node metastasis, 41 (82%) were positive for u-PA and 28 (56%) were positive for Nuc. In tumors without lymph node metastasis, 26 (52%) were positive for u-PA and five (10%) were positive for Nuc. The percentage of cases positive for u-PA or Nuc was significantly higher in tumors with lymph node metastasis than that in tumors without lymph node metastasis ( P < 0.01). The expression of u-PA was found to be significantly correlated with that of Nuc ( P < 0.001), mode of infiltrative growth ( P < 0.05), depth of invasion ( P < 0.01), and grade of lymphatic invasion ( P < 0.01). However, the expression of Nuc was found to be significantly correlated with the expression of Jun ( P < 0.05), depth of invasion ( P < 0.01), and grade of lymphatic invasion ( P < 0.001). These results suggest that immunohistochemical examination for the expression of u-PA and Nuc in tumor cells may help evaluate the potential of adenocarcinomas of the stomach for lymph node metastasis.     

Duodenal gangliocytic paraganglioma with regional lymph node metastasis and a glandular component

Gangliocytic paraganglioma (GP) is generally considered to be a benign periampullary lesion, although it is unclear whether it should be classified as a hamartoma or as a neoplasm. Here, we present a GP case with lymph node metastasis. A 16-year-old boy complained of exertional dyspnea. Upper endoscopy and imaging studies revealed a polypoid ampullary tumor. Pancreaticoduodenectomy with lymph node dissection was performed due to swelling of peripancreatic lymph nodes. Histologically, the tumor consisted of three cell types: epithelioid; spindle; and ganglion cells. In addition to these typical components of GP, a distinct glandular component was also present. There was substantial invasion of tumor cells into the lymphovascular vessels, associated with lymph node metastases. These lymph node metastases were histologically similar to the primary tumor. To judge from these findings GP may be a true neoplasm with metastatic capacity. Pre- and intraoperative investigations for lymph node or distant metastases are required for adequate resection of this kind of tumor.     

Perivascular epithelioid cell tumour (PEComa) of the soft tissue

AIMS: PEComa is a rare tumour developing from perivascular epithelioid cells (PEC) and is characterised by positive immunoreactivity for HMB45. Since PEComas are tumours having both a spindle cell component and an epithelioid and giant cell component, as seen in many sarcomas, as well as having a wide distribution in various organs and soft tissue, we reviewed cases originally diagnosed as sarcomas of the soft tissue in our institution and screened them by immunostaining for HMB45. METHODS: Consecutive soft tissue sarcomas (31 tumours) retrieved from the Surgical Pathology file at our institution for a period of 3 years were submitted for immunostaining for HMB45. Cases with positive HMB45 immunostaining were submitted for further immunostaining for MART1, CD68, S100 protein, cytokeratin AE1/3, EMA, vimentin, MSA and CD117. RESULTS: Of 31 sarcomas, three tumours in the group of 11 malignant fibrous histiocytomas (MFH) and unclassified sarcomas showed positive immunoreactivity for HMB45 and MART1 in 1-25% of tumour cells. The three tumours were located in the lower extremities and measured 8, 11 and 12 cm in diameter. Patient gender male:female was 2:1 and ages were 46, 56 and 60 years. Microscopically, the tumours were composed of a variable proportion of spindled cells, multinucleated cells and epithelioid cells disposed in diffuse sheets or nests. Mitotic figures and necrosis were frequent. The immunoreactivity was diffuse for CD68, focal for AE3 and EMA, negative or focal for MSA and CD117, and negative for S100 and AE1. All three patients developed lymph node or distant metastases and died of the disease within 1-2 years. CONCLUSIONS: PEComa re-screened from the group of high grade sarcomas without definite differentiation range from pleomorphic to monomorphic cytohistopathological features. Immunostaining for HMB45 of unclassified sarcomas is useful for the classification of these tumours. They occur preferentially in the lower extremities and have a high malignant potential when associated with large size, tumoural necrosis and high mitotic activity.     

肾脏上皮样血管平滑肌脂肪瘤的病理观察

目的对肾脏上皮样血管平滑肌脂肪瘤（epithelioid agiomyolipoma,EAML）的病理诊断、鉴别诊断和预后进行分析。方法2例肾脏EAML（其中1例为复发病例）,复习其临床资料,病理学检查包括常规病理学、免疫组织化学和超微结构,并进行随访。结果光镜下肿瘤均主要由具有多形性和不典型性的上皮样细胞组成,部分区域有明显的血管周上皮样排列;可见出血和坏死;并可见静脉内瘤栓;淋巴结内可见上皮样肿瘤细胞累及。免疫组织化学肿瘤细胞（包括淋巴结内肿瘤）HMB45、平滑肌肌动蛋白（SMA）、神经元特异性烯醇化酶（NSE）和波形蛋白弥漫阳性;S-100、melanpan和CD68散在阳性;而上皮细胞膜抗原（EMA）、AE1／AE3、CK7、CD117、肌肉特异性肌动蛋白（MSA）、结蛋白、白细胞共同抗原（LCA）、CD20、CIM5RO、CD30、CD15、嗜铬素（CgA）、突触素（Syn）、bcl-2、雌孕激素受体（ER、PR）和p53均为阴性。电镜检查可见一些肿瘤细胞内有黑色素小体样的致密颗粒、肌丝、密体,肿瘤细胞外可见不连续的基膜。2例患者手术后10个月状态良好,无肿瘤局部复发和转移征象。结论血管周上皮样排列、寻找经典血管平滑肌脂肪瘤的结构和肿瘤细胞表达HMIM5和SMA对于诊断和鉴别诊断至关重要。而细胞的不典型性、出血坏死和核分裂象可能只表明肿瘤的恶性潜能：淋巴结受累、肾静脉瘤栓不是恶性的诊断依据：只有远处转移才是恶性的证据。     

小细胞肺癌中CD24的表达及与微血管密度关系

目的检测CD24在小细胞肺癌(small cell lung cancer,SCLC)原发灶、淋巴结转移灶中的表达,探讨其与SCLC临床参数、侵袭转移及微血管密度(micro-vascular density,MVD)关系。方法应用免疫组化检测45例SCLC原发灶、33例区域淋巴结转移灶CD24表达及CD34-MVD。结果 SCLC原发灶、淋巴结转移灶CD24阳性率分别为53.3%(24/45)和60.6%(20/33),CD24阳性癌细胞常在癌巢周围密集分布,多见于侵袭边缘。CD34主要表达于血管内皮细胞胞膜,呈条索状甚至形成小管腔,主要位于癌巢边缘或癌细胞密集区;CD24、MVD与患者性别、年龄、肿瘤直径无关,而与淋巴结转移及胸膜侵袭有关(P<0.05);SCLC原发灶和淋巴结转移灶CD24阳性组MVD(33.44±8.51、47.65±14.31)均高于CD24阴性组(20.40±6.44、30.64±10.20)(P<0.05)。结论 CD24表达与SCLC侵袭转移行为和MVD有关。     

A resected case of neuroendocrine carcinoma of the stomach with unusual lymph node metastasis

Gastric endocrine cell carcinoma is a relatively rare tumor. We experienced a case of early gastric cancer in which an endocrine cell carcinoma was identified within a differentiated adenocarcinoma, and a component of this endocrine cell carcinoma had metastasized to lymph nodes of the stomach. In its 2010 revision regarding digestive system tumors, WHO classified cancer cells with characteristics of both glandular system cells and neuroendocrine cells as mixed adeno neuroendocrine carcinoma (MANEC) under the neuroendocrine carcinoma (NEC) category. In this case, we observed an endocrine cell carcinoma continuous with an intramucosal differentiated adenocarcinoma, and cancer cells with an irregular gland duct structure were observed in the proliferative portion of the submucosal tissue. In addition, there was a 35 mm size lymph node metastasis in the lesser curvature of the stomach consisting entirely of poorly differentiated cancer cells with polymorphic, highly atypical nuclei and scant cytoplasm. Immunohistological analysis showed that the endocrine carcinoma in the gastric mucosa was chromogranin A positive and the infiltrated area of the submucosal tissue was also chromogranin A positive. The lymph node metastasis was positive not only for chromogranin A, but also for Synaptophysin and CD56. Furthermore, the Ki67 labeling index was high at approximately 80 % for the gastric endocrine cell carcinoma and approximately 90 % for the lymph node metastases. Until now, there are no reports related to the patients with early gastric cancer accompanied with lymph node metastasis of MANEC. This case is very interested in considering the mechanism of lymph node metastasis of MANEC. The patient has shown no sign of recurrence for 1 year and 4 months after postoperative chemotherapy.     

Spontaneous regression of breast cancer with axillary lymph node metastasis: a case report and review of literature

Spontaneous regression (SR) of cancer is a rare but well-documented biological phenomenon. However, the mechanism remains to be elucidated. We herein report a case of the SR of breast cancer at both the primary site and metastatic axillary lymph node with spontaneously-induced T cell-mediated immunological responses. A 52-year-old female with a lump in the left axilla was diagnosed to have a small breast carcinoma with a distinct axillary lymph node metastasis. During the preoperative systemic examination, she was diagnosed to have severe type 2 diabetes mellitus, was treated with insulin, and the hyperglycemia was normalized after one month. Surgery for left breast cancer was then performed. The postoperative histopathological examination revealed the SR of breast cancer at both the primary site and metastatic axillary lymph node. Immunohistochemical studies revealed that estrogen receptor positive, AE1/AE3-positive ductal carcinoma completely underwent necrosis associated with extensive infiltration of CD3-positive T cells in the tumor nodule in the lymph node. In addition, primary ductal carcinoma cells also underwent single cell necrosis with infiltration of T cells with lymph follicle-like organization of B cells in the mammary gland. The features were suggestive that the tumor eradication in the metastatic lymph node and regression of the primary ductal carcinoma could be due to host T cell response to the ductal carcinoma. As far as we know it is the first report that shows the spontaneous regression of breast cancer, probably due to the spontaneously-induced T cell response.     

乳腺癌组织蛋白酶D和PSA表达与同侧腋淋巴结转移的关系

目的：探讨乳腺癌中组织蛋白酶Ｄ（ｃａｔｈｅｐｓｉｎＤ，ＣＤ）和前列腺特异性抗原（ＰＳＡ）的表达与同侧腋淋巴结转移的关系。方法：应用ＬＳＡＢ免疫组化法检测ＣＤ和ＰＳＡ在７８例乳腺癌中的表达，其中伴同侧腋淋巴结转移者３６例。结果：（１）７８例乳腺癌ＣＤ阳性表达率４１．０３％（３２／７８），ＰＳＡ阳性表达率４３．５％（３４／７８）；（２）同侧腋淋巴结转移组ＣＤ阳性表达率６９．４４％（２５／３６），无同侧腋淋巴结转移组ＣＤ阳性表达率１６．６７％（７／４２），差异有高度显著性（Ｐ＜０．０１）；（３）同侧腋淋巴结转移组ＰＳＡ阳性表达率２５．０％（９／３６），无同侧腋淋巴结转移组ＰＳＡ阳性表达率５９．５２％（２５／４２），差异有高度显著性（Ｐ＜０．０１）。结论：ＣＤ和ＰＳＡ的表达可作为乳腺癌预后检测的参考指标。ＣＤ表达阳性率与同侧腋淋巴结转移呈正相关，与预后负相关；而ＰＳＡ表达阳性率与同侧腋淋巴结转移呈负相关，与预后正相关     

Usefulness of immunohistochemistry for recognizing metastatic colorectal adenocarcinoma in infarcted lymph nodes

Lymph node infarction is a spontaneous coagulative necrosis of the affected lymph node and is frequently associated with concurrent and subsequent malignant lymphoma. However, this phenomenon appears to be rarely associated with metastatic carcinomas. Here, we report on the histopathologic and immunohistologic findings of three cases showing lymph node infarction in the regional lymph node associated with metastatic colorectal adenocarcinoma. Histologically, coagulative necrosis of metastatic carcinoma was surrounded by a thick rim of granuloma consisting of histiocytes with or without epithelioid features, foamy cells, and a small number of lymphocytes. The immunohistochemical study of the coagulative necrosis demonstrated that cytokeratins (AEI/AE3 and CAM5.2) and carcinoembryonic antigen (CEA) were well preserved in all three cases. However, compared with viable tumor tissues, only a few tumor cells were positive for epithelial membrane antigen. Using formalin-fixed and paraffin-embedded tissues, immunostaining for cytokeratins and CEA of the lymph node containing necrotic carcinoma may provide clinically valuable information.     

Immunoreactivity for IL-1 beta and TNF alpha in human lymphoid and nonlymphoid tissues.

Monoclonal antibodies (MAbs) against two non-cross-reacting antigens of human IL-1 beta (Vhp20 and BRhC3) and human TNF alpha (B154.2 and B154.7) were applied to identify cytokine-containing cells in tissue sections and in cell suspensions. IL-1 beta- or TNF alpha-positive cells were not present in immunostained cytocentrifuge smears prepared from freshly isolated peripheral blood leukocytes, spleen, and lymph node cells. After 18 hours of culture with bacterial endotoxin (LPS), 80% to 90% of blood monocytes, 30% of spleen macrophages, and 2% to 28% of lymph node macrophages were strongly positive for IL-1 beta with either of the MAbs. Furthermore, 25% to 35% of blood monocytes and 6% to 60% of lymph node macrophages were stained for TNF alpha. Cells positive for IL-1 beta or TNF alpha were extremely rare in sections of normal thymus, spleen, and lymph nodes. Immunoreactivity for IL-1 beta or TNF alpha was frequently observed in sections of granulomatous lymphadenitis (N = 11). IL-1 beta or TNF alpha staining was confined to the epithelioid macrophages forming the granuloma, and the intensity of TNF alpha reactivity was generally stronger. The high frequency of cytokine-containing cells in this pathologic condition was confirmed in a cell suspension study showing that 20% of epithelioid macrophages were weakly positive for IL-1 beta and 80% were strongly positive for TNF alpha. The presence of cytokine-containing cells was investigated in cryostat sections of several nonlymphoid organs with normal histologic appearance. IL-1 beta reactivity was not observed in any of the tissues. TNF alpha reactivity was frequently demonstrated in isolated macrophages embedded in the interstitial connective tissue.     

Neuroendocrine breast carcinoma metastatic to renal cell carcinoma and ipsilateral adrenal gland

We report on a 60-year-old woman with neuroendocrine carcinoma of the left breast metastasizing to renal cell carcinoma (RCC) of the left kidney and to adrenal gland. A yellow, well-circumscribed tumor, 11 cm in largest diameter and limited to the kidney, was found. Histopathology revealed RCC with foci of neuroendocrine differentiation. Solid sheets of hyperchromatic epithelioid cells with high mitotic activity were found between typical clear cells of RCC. These cells were CAM5,2 and E-cadherin focally positive, synaptophysin and NSE weakly positive, CK19 moderately positive, and AE1-AE3 and EMA strongly positive. Chromogranin A, CD10, CK 14, CK 20, HER2 (score 1+), vimentin, and HMB45 were negative. The left adrenal gland contained multiple, separate foci of a tumor composed of neuroendocrine components. Because of the biphasic tumor in the kidney, extensive clinical examination and further analyses were recommended. Tumor in the left breast was revealed. Two months later, the patient underwent mastectomy with axillary lymph node dissection. The tumor was histologically and immunohistochemically similar to the neuroendocrine component within RCC. All axillary nodes were positive. To our knowledge, this is the first case of neuroendocrine breast carcinoma with metastasis to renal cell carcinoma and ipsilateral adrenal gland.     

Interdigitating dendritic cell sarcoma of lymph node mimicking granuloma: a case report and review of the literature

Interdigitating dendritic cell sarcoma (IDCS), is an extremely rare neoplasm. We report a case of a 77-year-old man presented with gradual lymph nodes enlargement in inguina, neck and axilla for 6 months. Biopsy revealed that part of the lymph node was replaced by several large granuloma-like nodules composed of mild atypical tumor cells, resembling epithelioid cells. Mitotic figures were hardly found. Immunohistochemistry showed that tumor cells were positive for S-100, CD68 and CD45. Ki-67 labeling index was 5%. To the best of our knowledge, this is the first case of IDCS showing granuloma-like growth pattern with mild atypical tumor cells.     

Oncocytic renal cell carcinoma with immunohistochemical properties of renal oncocytoma

Renal oncocytoma (RO) is a characteristic benign renal tumor. The existence of malignant RO is controversial and anecdotal, partly due to a lack of specific markers for RO. With recent advances in immunohistochemistry, RO can be distinguished from other renal neoplasms with routine stains and with the aid of immunostaining. We report two cases of renal neoplasms with similar histopathological appearances. They were characterized by oncocytic cytoplasm, numerous intra-cytoplasmic vacuoles, uniform round to oval hyperchromatic nuclei with remarkably thick nuclear membranes and prominent nucleoli. The tumor cells were closely packed and disposed in an alveolar pattern. The neoplastic cells were diffusely reactive for CD117 and progesterone receptor, and diffusely or focally reactive for cytokeratin AE1/AE3, and focally reactive for cytokeratin 7, CD10, and racemase. The cells were non-reactive for renal cell carcinoma (RCC) antigen, vimentin, S100, and neuroendocrine markers. One tumor showed lymph node metastasis. Due to the remarkable cytological atypia, lymph node metastasis, and similar immunological features of RO, these two tumors likely represent a distinct subtype of RCC related to RO.     

Malignant pulmonary epithelioid hemangioendothelioma with hilar lymph node metastasis

Few cases each of malignant pulmonary epithelioid hemangioendothelioma (PEH) and PEH with lymph node metastasis have been reported. Here we report a case of PEH with lymph node metastasis. A Japanese woman was found to have a 2-cm-diameter mass with small satellite nodules in the right upper lobe of the lung. Microscopic examination revealed solid destructive growth of the main tumor, with epithelioid cells showing cytologic atypia and 3 mitotic figures per 10 high-power fields. Some of the tumor cells had intracytoplasmic lumina that appeared as vacuoles. These lumina were negative for alcian blue and periodic acid Schiff, and contained erythrocytes. However, erythrocytes were seen more frequently within small but distinct vascular channels that were arranged diffusely in the periphery of the main tumor. Other satellite nodules showed conventional PEH morphology. In hilar lymph nodes, the tumor cells resembled those of the main tumor. The vascular origin of the main tumor and satellite nodules was demonstrated by positive immunoreactivity for some endothelial markers. Although the diagnostic features of malignant PEH are not clear, those for PEH in other organs have included nuclear atypia, many mitoses, presence of necrosis, large tumor size, and spindle cell proliferation. The present case met these criteria, except for large tumor size and spindle cell proliferation. In conclusion, atypical cytologic features, the presence of necrosis, a high Ki-67 labeling index, and accompanying nodules of conventional PEH in the same pulmonary lobe suggest that this case was a malignant PEH with hilar lymph node metastasis.     

血管内皮生长因子C和nm23表达与微血管密度及宫颈癌转移的关系

目的探讨血管内皮生长因子-C(vascular endothelial growth factor-C,VEGF-C)和nm23(non-metastasis23)表达与微血管密度(microvessel density,MVD)及宫颈癌转移的关系。方法采用免疫组化SABC法检测16例正常宫颈上皮及68例宫颈癌中VEGF-C、nm23的表达。并用CD105标记新生血管内皮细胞,计算肿瘤内MVD。结果VEGF-C在宫颈癌组织中的阳性表达率显著高于正常组织(P<0.01),淋巴结转移组VEGF-C阳性率高于无淋巴结转移组(P<0.05),VEGF-C表达强度与MVD呈正相关(P<0.05)。nm23蛋白表达率显著低于正常组织(P<0.01),淋巴结转移组nm23阳性率低于无淋巴结转移组(P<0.05)。nm23在宫颈癌中的表达与VEGF-C呈负相关(P<0.01)。结论宫颈癌组织VEGF-C呈高表达、nm23呈低表达,可能在宫颈癌血管生长、肿瘤浸润转移过程中起重要作用。检测宫颈癌中VEGF-C、nm23表达对进一步了解宫颈癌局部血管生成情况及判断预后有一定的应用价值。     

非小细胞肺癌生物学特性与神经内分泌分化的关系

目的：探讨非小细胞肺癌神经内分泌（neuroendocrine,NE)分化与肺癌生物学特性的关系。方法：采用免疫组化LSAB法检测有随访资料（8年）的53例非小细胞肺癌（non small cell lung carcinoma,NSCLC)神经内分泌标志。结果：NSCLC表达NSE、S－100蛋白、chromogranin A(CgA)和synaptophysin(Syn)阳性率分别为28．3％（15／53）、66．7％（39．53）、0／53和3．8％（2／53）。NSCLC伴NE分化与瘤体分期（Tstage)、治疗后肿瘤易复发和转移相关；有淋巴结转移的NSCLC患者3年和5年生存率低。结论：部分NSCLC伴NE分化，伴NE分化的NSCLC瘤体分期高、经综合治疗后肿瘤易复发和转移。有淋巴结转移的NSCLC患者预后差。     

胰腺实体-假乳头状肿瘤32例临床病理分析及TFE3表达的诊断价值

目的 探讨胰腺实性-假乳头状肿瘤(solid-pseudopapillary neoplasms,SPN)的临床病理特征及转录因子E3(transcrip-tion factor E3,TFE3)表达在诊断中的价值.方法 采用免疫组化法检测32例胰腺SPN中TFE3、β-catenin、CD10、CK、vimen-ti...     

Expression of CD56 antigen in Langerhans cell histiocytosis associated with T-lymphoblastic lymphoma in a same lymph node

Association of T-lymphoblastic lymphoma (LBL) and Langerhans cell histiocytosis (LCH) in the same lymph node is very rare. Herein, we report such two cases with expression of CD56 in Langerhans cells. Immunohistochemically, lymphoblasts were positive for anti-polyclonal CD3 antibody, CD34, CD7, CD99, and terminal deoxynucleotidyl transferase. LCH cells were positive for anti-S100 protein, CD1a, CD4, CD56, and CD68. Although those two populations were separated topographically, many histiocytes intermingled with lymphoblasts in the paracortex and a few lymphoblasts were scattered within the intrasinusoidal sheets of histiocytes. Neither admixed eosinophils nor multinucleated giant cells were observed. The pathogenetic mechanism of CD56 expression in LCH associated with LBL is discussed.