睾丸原发性神经内分泌肿瘤临床病理研究(附7例报告)

目的:观察睾丸原发性神经内分泌肿瘤的组织学、免疫表型,探讨其临床病理特征、诊断、鉴别诊断及治疗预后。方法:运用组织学、免疫组化技术对7例睾丸原发性神经内分泌肿瘤进行光镜观察及免疫标记,并结合相关文献对其临床表现、组织形态和免疫组化特点及治疗和预后等进行综合分析。结果:7例男性患者均以睾丸无痛性肿块就诊,平均40.6岁。均不伴有类癌综合症。组织学上,肿瘤排列呈岛状、梁状,可见实性片状及大的不规则腺管样结构,瘤细胞大小较一致,呈圆形、多角形,胞质略嗜酸,胞界不清。核单一,圆形,染色质细颗粒状,核分裂象计数2个/10HPF。免疫表型,瘤细胞均弥漫性表达Syn、CgA、NSE和CK,Ki-67阳性细胞数2%。结论:原发于睾丸的神经内分泌肿瘤非常罕见,通常不伴有类癌综合症,早期手术切除预后较好。免疫组化染色有助于该肿瘤诊断,鉴别诊断包括睾丸畸胎瘤合并类癌、转移性神经内分泌肿瘤、精原细胞瘤、支持细胞瘤等。     

睾丸原发性神经内分泌癌1例报告并文献复习

目的：探讨睾丸原发性神经内分泌癌的起源、诊断要点和治疗方法,提高对该疾病的认识。方法：回顾性分析我院收治的1例睾丸原发性神经内分泌癌患者的资料,并复习有关文献。结果：患者左侧睾丸有一无痛肿块,质硬。彩超扫描证实左侧睾丸内存在一2．7cmX2．3crux3．1cm低回声实性团块,包膜完整,界限清楚,肿块内血流信号丰富;腹膜后、腹股沟彩超检查未见肿大淋巴结。血清肿瘤标记物pHCG、CEA和AFP未见异常。手术完整切除肿瘤,术后病检提示为睾丸神经内分泌癌。病变组织起源于神经内分泌细胞,癌细胞类圆形,胞质伊红染,核圆形,颗粒状,癌细胞呈巢状或岛状排列。癌细胞弥漫性表达突触素、嗜铬颗粒A和细胞角蛋白。结论：睾丸原发性神经内分泌癌罕见,临床表现缺乏特异性,组织学特点和免疫组化标记物是诊断该病的主要依据,需与转移性类癌和混合性类癌相鉴别。早期诊断并手术效果良好,术后应密切随访预防复发和转移。     

超声检查在睾丸肿瘤诊断与鉴别诊断中的价值初探

目的:探讨超声检查在睾丸肿瘤诊断与鉴别诊断中的价值。方法:对我院1998～2005年172例睾丸肿块的超声图像结合其手术及病理结果进行回顾性分析。结果:172例睾丸肿块中超声诊断50例睾丸血肿,13例睾丸囊肿,26例睾丸炎性结节,25例睾丸结核,58例睾丸肿瘤;睾丸肿瘤中50例为生殖细胞瘤,其中精原细胞瘤41例,非精原细胞性生殖细胞瘤(NSGCT)9例;6例为非生殖细胞瘤;3例为继发性肿瘤。超声检查发现典型精原细胞瘤、畸胎瘤、表皮样囊肿、间质细胞瘤及多发性的恶性淋巴瘤具有较为特征性的声像图。结论:超声检查可以对睾丸肿瘤作出初步的诊断和鉴别诊断,为进一步治疗方案的制定提供依据,是睾丸肿瘤的首选影像学检查方法。     

睾丸原发性类癌病例分析并文献复习

目的探讨睾丸原发性类癌的发生机制、组织来源、临床病理特点和鉴别诊断。方法对1例术前经穿刺活检诊断为右侧睾丸类癌患者,行患侧睾丸根治性切除术。标本送病理检查。结果术中发现右侧精索、输精管、睾丸、附睾鞘膜光滑,与周围组织无粘连浸润,术后纵行剖开标本见肿物呈实性,大小为3.5cm×3.0cm×1.8cm,切开肿瘤内含黄色断面。右侧睾丸大小约4.5cm×5.0cm×5.5cm,内有一灰白色占位,大小约3.5cm×3.0cm×1.8cm。结论睾丸原发性类癌是一种罕见的睾丸肿瘤,其组织起源有争议。该肿瘤应与精原细胞瘤、转移性类癌、支持细胞瘤及粒层细胞瘤等睾丸肿瘤常见病理类型相鉴别。     

胃肠道类癌的诊断及外科治疗

类癌这一名词诞生于本世纪初，1907年Obern－dorfer用“karzinoid”来描述一组生长缓慢、低度恶性的肿瘤，随后发现这类肿瘤来源于消化道具有嗜银特性的Lieberkuhn肠腺。1953年Lembeck发现这类肿瘤细胞可以分泌卜羟色胺，1969年Pearse发现该类细胞具有摄取胺前体和脱羧基的作用，随后，由于免疫组织化学技术的发展及应用，人们发现类癌细胞可以产生许多肽类和胶类的激素物质，因此，人们对类癌的命名和归类提出了质疑。在1980年世界卫生组织的分类中，人们将许多神经内分泌系统的肿后统称为“类癌”，但其中不包括胰岛细胞瘤．甲状腺出样…     

男性生殖系统胚胎性横纹肌肉瘤的临床病理学研究

目的:探讨男性生殖系统胚胎性横纹肌肉瘤(ERMS)的临床病理特征、诊断及鉴别诊断。方法:收集2000~2015年我院诊治的11例男性生殖系统ERMS的临床病理、免疫表型和电镜特征相关资料,并复习相关文献。结果:11例男性生殖系统ERMS的发病年龄9~58岁,中位年龄17岁;发病部位睾丸3例、阴囊4例、附睾1例、前列腺3例。临床表现无特异,难以与炎性病变及其他良性病变区分。组织学:肿瘤细胞呈弥漫状或束状分布,主要由核深染的短梭形、圆形或不规则形细胞组成,瘤细胞胞质红染,部分强嗜酸性,有横纹肌分化,部分瘤细胞较幼稚,部分可见网球拍状细胞,部分胞质有空泡变性,核呈类圆形或短梭形,部分可见核仁,见核分裂象,部分可见网球拍状细胞。免疫表型:肿瘤细胞表达Myogenin(5/6)、Desmin(11/11)、Myo D1(8/9)和Myosin(1/2)。1例电镜观察:瘤细胞胞质内可见早期肌原纤维。结论:男性生殖系统ERMS是一种较为罕见、好发于年轻人的高度恶性肿瘤。确诊主要根据其组织学形态和免疫表型,必要时可结合电镜观察辅助诊断。ERMS具有局部侵袭性强、多早期扩散,采用早期手术切除、辅以放疗和化疗的综合治疗可减少复发、提高患者生存率。     

标志性基因在涎腺乳腺样分泌性癌诊断中的临床价值

目的:探讨涎腺乳腺样分泌性癌（mammary analogue secretary carcinoma of salivary gland,MASC）标志性基因在临床病理学的特征、诊断、鉴别、免疫表型及其预后中的价值。方法:收集2018年1月至2021年1月宁波市临床病理诊断中心涎腺MASC患者28例作A组,另选取腺泡...     

肾脏黏液性管状及梭形细胞癌的临床病理观察

目的探讨肾脏黏液性管状及梭形细胞癌（mucinous tubular and spindle cell carcinoma,MTSCCa）的临床病理特点、免疫表型及鉴别诊断要点,并复习相关文献对其组织起源作一探讨。方法对1例肾脏黏液性小管状和梭形细胞癌进行临床病理学特征及免疫组化的分析。结果患者女性,56岁,无特异临床症状,体检发现右肾占位。巨检发现肾上极实质内一灰白界清结节,直径7cm,切面均匀。镜下见瘤细胞主要呈两种结构：由单层立方细胞排列成的细管状结构及类似于平滑肌瘤的梭形细胞结构,局部可见透明细胞及乳头样结构,立方状细胞及梭形细胞均形态温和。背景中见大量黏液,并可见淋巴细胞、浆细胞及泡沫细胞浸润。免疫组化：CK7、CK18、Vim阳性表达;SMA、HMB45、SYN均阴性。结论MTSCCa是一种少见的低级别肿瘤,预后较好,可能来源于远端肾单位。     

睾丸混合性非精原细胞性生殖细胞癌1例并文献复习

目的:睾丸混合性非精原细胞性生殖细胞癌的文献报道极少,本文旨在探讨睾丸混合性非精原细胞性生殖细胞癌的临床症状、病理特点及诊疗方法。方法:分析1例睾丸混合性非精原细胞性生殖细胞癌的临床资料,并运用组织学、细胞化学和免疫组化技术对该例睾丸混合性非精原细胞性生殖细胞癌进行光镜观察和免疫标记并结合文献就该类肿瘤的临床特征进行探讨。结果:患者以睾丸无痛性肿大3年就诊,病理组织学表现为肿瘤排列结构多样,有乳头状结构、裂隙或腺样结构,细胞大,呈多角形或柱状,核不规则呈泡状,一个或多个核仁,核膜清楚,胞质嗜碱或嗜酸,间质少量淋巴细胞浸润。免疫组化显示:白细胞分化抗原(CD117)(-)、细胞角蛋白(CK8-18)(++)、CD30(++)、CK(+++)、波形纤维蛋白(Vimentin)(-)、胎盘型碱性磷酸酶(PLAP)(±)、抑癌基因产物(P53)(+)、甲胎蛋白(AFP)(+)和上皮膜抗原(EMA)(++)。病理诊断为睾丸畸胎胚胎癌,行手术根治术,按混合性非精原细胞性生殖细胞癌行术后辅助化疗。随访时间l年,健康生存。结论:睾丸混合性非精原细胞性生殖细胞癌是一种罕见的恶性肿瘤,多数临床症状不明显。诊断主要依靠体格检查、B超、CT、血清肿瘤标记物测定等,确诊需要病理学检查,手术切除是其首选的治疗方法。     

肾上腺外恶性肿瘤伴发肾上腺原发肿瘤的临床特点

目的 了解肾上腺外恶性肿瘤伴发肾上腺原发肿瘤的临床特点.方法 1990年至2004年收治有恶性肿瘤病史或同期其他部位恶性肿瘤伴肾上腺原发肿瘤患者13例.男10例,女3例.中位年龄47岁.肾上腺肿瘤位于左侧6例、右侧4例、双侧3例.肿瘤最大直径中位数4.0cm.肾上腺外肿瘤分别为结直肠腺癌4例、甲状腺髓样癌3例、肺癌2例,乳腺癌、前列腺癌、膀胱癌和十二指肠类癌各1例.结果 原发肾上腺肿瘤13例,占同期肾上腺伴有恶性肿瘤病史或同期其他部位恶性肿瘤的30%(13/44).其中肾上腺皮质腺瘤8例、嗜铬细胞瘤3例、皮质腺癌和血管瘤各1例.8例皮质腺瘤中,B超、CT和MRI诊断准确率分别为3/8、3/7和4/4;3例嗜铬细胞瘤患者均为甲状腺髓样癌术后,B超、CT或MRI检查均确诊;1例肾上腺血管瘤B超、CT或MRI扫描均误诊为转移.失随访1例.伴发肾上腺腺瘤患者8例中,6例无瘤生存3～8年.嗜铬细胞瘤3例无瘤生存8～12年,但2例术后肾上腺皮质功能不全需要激素替代.肾上腺血管瘤患者术后长期生存12年.结论有恶性肿瘤病史患者伴发的肾上腺原发肿瘤以腺瘤多见,影像学是定性、定位诊断的主要手段.对于肾上腺外恶性肿瘤伴发孤立的原发与转移不明的肾上腺肿瘤,建议手术切除.     

Rete testis-associated nodular steroid cell nests: description of putative pluripotential testicular hilus steroid cells

A putative hilus interstitial cell has been proposed as the cell of origin for testicular tumors of adrenogenital syndrome, but its normal histology is not documented. We present hitherto undescribed nodular steroid cell nests associated with the rete testis that are distinctive in their morphology and immunohistochemical profile from Leydig cells and do not have the morphology of typical extra-adrenal cortical rests. These nodules measured 1, 1, 1.8, 2, and 2.5 mm in size with a distinct sinusoidal vasculature. Individual cells were rounded to polygonal with evenly distributed moderate-to-abundant eosinophilic cytoplasm. The nuclei were homogenous and round, with fine chromatin and ocasionally with prominent nucleoli. The differential diagnosis included adrenocortical rests, testicular adnexal Leydig cells, carcinoid tumorlets, paraganglionic rests, and adenomatoid mesothelial proliferation. Immunohistochemistry showed positivity for melan A (5/5), inhibin (3/5), and calretinin (2/4), although the immunoreactivity was distinctively different from the concurrent intratesticular Leydig cells and testicular adnexal Leydig cells in all cases. The unique morphology, immunophenotype, and distinctive location of these cells in the testicular mediastinum raises the possibility that these cells represent testicular hilus steroid cells, the putative histogenetic cell implicated for testicular tumors of adrenogenital syndrome. We propose to name these proliferations rete testis-associated nodular steroid cell nests.     

Horseshoe Kidney is Associated With an Increased Relative Risk of Primary Renal Carcinoid Tumor

Purpose

Carcinoid tumor is a rare neoplasm of the kidney with an unknown histogenesis. Of only 31 cases previously reported in the literature 4 arose within horseshoe kidneys. We report a case of primary carcinoid tumor arising within a horseshoe kidney and discuss the unique insight it provided into the pathogenesis of this tumor.

Materials and Methods

We reviewed in detail all 31 reported cases of renal carcinoid tumor and, using reported incidence rates of horseshoe kidney, we calculated the relative risk of renal carcinoid tumor arising within a horseshoe kidney. Immunohistochemical staining for neuroendocrine related markers was performed on tissue sections from the present carcinoid tumor, the adjacent kidney and 5 control samples of normal renal parenchyma.

Results

Of the reported tumors 15.6% occurred in horseshoe kidneys, yielding a calculated relative risk of 62. The present tumor was multifocal, arising from the wall of a cystic lesion and possibly representing a dilated calix within the isthmus. Intestinal epithelium lining the cyst cavity exhibited multifocal neuroendocrine cell hyperplasia with an immunohistochemical profile identical to that of the carcinoid tumor cells.

Conclusions

The relative risk of renal carcinoid tumor developing in a horseshoe kidney is markedly greater than that for Wilms tumor or transitional cell carcinoma. The clinical course of renal carcinoid tumor arising within a horseshoe kidney appears to be more benign than that of the nonhorseshoe variant. Our observations support the hypothesis that renal carcinoid tumors may arise from neuroendocrine cells within foci of metaplastic or teratomatous epithelium within the kidney.     

Acinar cell carcinoma of the pancreas metastatic to the ovary: a report of 4 cases

We report 4 cases of acinar cell carcinoma of the pancreas, 3 presenting as metastases in the ovary, the first report of this circumstance, which may pose a broad differential diagnosis and caused significant diagnostic difficulty in all the cases. The average patient age was 57 (range: 28 to 81) years. In 3 cases, the ovarian tumors were detected before the pancreatic tumor; in 1 case, a large abdominal mass and ovarian tumors were discovered synchronously. The ovarian tumors were large, solid, white-tan on gross examination, and bilateral in 3 cases; the single case involving only 1 ovary had 2 discrete masses of tumor. Microscopic examination showed highly cellular neoplasms with a small amount of fibrous stroma. Two cases had a predominant acinar growth pattern of cells with brightly eosinophilic, granular cytoplasm. In 2 cases, the pattern was predominantly solid-cribriform with areas of comedolike necrosis, and the cells had pale eosinophilic, finely granular cytoplasm. Nuclei in all cases were uniform with prominent nucleoli. The main differential diagnostic consideration was well-differentiated neuroendocrine neoplasm (carcinoid tumor); positive immunostaining with antibodies against chymotrypsin and trypsin and negative immunostaining with antibodies against synaptophysin and chromogranin helped exclude this diagnosis. We observed focal alpha-inhibin immunostaining in 2 cases, which may represent a potential diagnostic pitfall, as a Sertoli cell tumor or unusual granulosa cell tumor may also enter the differential diagnosis. Inclusion of antibodies against the pancreatic enzymes chymotrypsin and trypsin in the immunohistochemical panel is critical in establishing the correct diagnosis and should be considered when evaluating ovarian tumors with architectural (mainly acinar) and cytologic (granular eosinophilic cytoplasm) characteristics that should bring a metastatic acinar cell carcinoma into consideration.     

Thymus carcinoid producing parathyroid hormone (PTH)-related protein: Report of a case

We report herein the rare case of a thymus carcinoid producing parathyroid hormone (PTH)-related protein (PTHrP) found in a 43-year-old Japanese man who presented with a 19-month history of dyspnea. The diagnosis of a carcinoid was established by light microscopic, electron microscopic, and immunohistochemical examinations. The tumor was considered to be thymic in origin because of its anatomic location, the presence of feeders to the tumor (derived from the internal thoracic arteries), and the fact that no other tumors from which it could have originated were found. After an excisional biopsy, which revealed PTH-related immunoreactivity in the tumor cells, 60 Gy of irradiation was delivered, resulting in a 48% reduction in the size of the tumor. Flow cytometry showed a diploid DNA pattern, with 94% of the cells in the GI phase, 4% in the S phase, 2% in the G2+M phase, and a G2+M/Gl ratio of 1.95. The primary cell culture showed some cells adopted in a cord-like pattern. To our knowledge, this is the first report of a carcinoid tumor in which positive staining for PTHrP by immunohistochemical methods was demonstrated.     

Comparative analysis of alternative and traditional immunohistochemical markers for the distinction of ovarian sertoli cell tumor from endometrioid tumors and carcinoid tumor: A study of 160 cases

The main neoplasms in the differential diagnosis for primary ovarian tumors with a tubule-rich pattern are pure Sertoli cell tumor, endometrioid tumors (including borderline tumor, well-differentiated carcinoma, and the sertoliform variant of endometrioid carcinoma), and carcinoid tumor. Because traditional immunohistochemical markers [pan-cytokeratin (pan-CK), low molecular weight cytokeratin (CK8/18), epithelial membrane antigen (EMA), inhibin, calretinin, CD99, chromogranin, and synaptophysin] can occasionally have diagnostic limitations, the goal of this study was to determine whether or not any alternative markers [cytokeratin 7 (CK7), estrogen receptor (ER), progesterone receptor (PR), CD10, and CD56] have better diagnostic utility when compared with traditional markers for this differential diagnosis. Immunohistochemical stains for alternative, as well as traditional, markers were performed on the following primary ovarian tumors: pure Sertoli cell tumor (n = 40), endometrioid borderline tumor (n = 38), sertoliform endometrioid carcinoma (n = 13), well-differentiated endometrioid carcinoma (n = 27), and carcinoid tumor (n = 42). Extent and intensity of immunostaining were semiquantitatively scored. In addition, immunohistochemical composite scores (ICSs) in positive cases were calculated on the basis of the combination of extent and intensity scores. Cytokeratin 7 (CK7) was positive in 97% of endometrioid tumors, 13% of Sertoli cell tumors, and 24% of carcinoid tumors. The differences in the mean ICSs for endometrioid tumors versus Sertoli cell tumor or carcinoid tumor were statistically significant (P values ranging from <0.001 to 0.018). ER and PR were positive in 87% and 86% of endometrioid tumors, 8% and 13% of Sertoli cell tumors, and 2% each of carcinoid tumors, respectively. The differences in the mean ICSs for endometrioid tumors versus Sertoli cell tumor were statistically significant (P values ranging from <0.001 to 0.012). Among the epithelial markers, EMA seemed to be the most discriminatory but only slightly better than CK7, ER, or PR. Pan-CK and CK8/18 were not helpful. CD10 showed overlapping patterns of expression in all categories of tumors. Among the sex cord markers, CD10 was markedly less useful than inhibin or calretinin; CD99 was not discriminatory. CD56 showed overlapping patterns of expression in all categories of tumors. Among the neuroendocrine markers, CD56 was less useful than chromogranin or synaptophysin. When traditional immunohistochemical markers are problematic for the differential diagnosis of ovarian Sertoli cell tumor versus endometrioid tumors versus carcinoid tumor, adding CK7, ER, and/or PR to a panel of markers can be helpful. Endometrioid tumors more frequently express CK7, ER, and PR and show a greater extent of immunostaining in contrast to Sertoli cell tumor and carcinoid tumor. Compared with traditional epithelial markers, CK7, ER, and PR are nearly as advantageous as EMA. Inhibin is the most discriminatory sex cord marker, and CD10 is not helpful in the differential diagnosis. Chromogranin and synaptophysin are excellent discriminatory markers for carcinoid tumor, and CD56 is neither sufficiently sensitive nor specific enough for this differential diagnosis to warrant its use in routine practice.     

原发性膀胱透明细胞癌(附二例报告并文献复习)

目的：探讨原发性膀胱透明细胞癌的临床、病理、组织化学特性和诊治方法。方法：回顾分析2例患者临床资料，结合文献复习讨论。结果：2例肿瘤发生于膀胱右侧壁近膀胱颈处，以血尿就诊。组织学以大片透明样癌细胞、腺管样结构为特征。电镜下癌细胞核大而畸形，细胞器较少，部分癌细胞内有细胞内微小腺腔。免疫组化示PAS（＋）、AB（＋）。1例行膀胱部分切除术，30个月后出现淋巴结转移；1例行肿瘤电切术，15个月后未见复发。结论：此病以血尿为主要症状，病理检查才能确诊，应与转移性癌及肾源型腺瘤相鉴别，治疗以根治性手术为主，预后较其他非尿路上皮癌好。     

睾丸混合性生殖细胞肿瘤临床病理分析

目的:探讨原发性睾丸混合性生殖细胞肿瘤(MGCT)的临床病理特征。方法:对我院13例原发性睾丸MGCT患者的临床病理资料进行回顾性分析,并结合相关文献进行讨论。结果:睾丸MGCT占我院同期睾丸生殖细胞肿瘤的24.1%(13/54),患者年龄2~53岁,平均28.3岁。全部病例均发生于单侧睾丸,左侧6例,右侧7例,左右侧比为0.86∶1。睾丸MGCT病理形态多样,肿瘤成分包括胚胎性癌(11例,84.6%)、精原细胞瘤(8例,61.5%)、畸胎瘤(6例,46.2%)、绒毛膜癌及卵黄囊瘤(均为4例,23.1%)。其中9例(69.2%)包含2种不同的生殖细胞肿瘤成分,3例(30.8%)包含3种不同的肿瘤成分,1例(7.7%)包含5种不同的肿瘤成分。结论:睾丸MGCT非常少见,好发于青壮年男性,不同的肿瘤成分其生物学行为、临床治疗和预后不同,因此准确的病理诊断非常必要,免疫组化标记对病理诊断与鉴别诊断具有重要作用。     

Metastatic carcinoma to the testis: a clinicopathologic analysis of 26 nonincidental cases with emphasis on deceptive features

Metastatic carcinomas to the testis may simulate primary testicular neoplasms, even in patients with known extratesticular primaries, but information on this topic is limited. We therefore reviewed our experience with 26 cases from consultation (N=23) or hospital (N=3) files; none of the cases were from autopsy material or incidentally discovered in therapeutic orchiectomies from patients with prostate cancer. The tumors occurred in men 29 to 90 years old, with the prostate the most common primary site (N=11), followed by the renal parenchyma (N=4), colon (N=4), urinary tract (N=3), lung (N=2), esophagus (N=1), and, most probably, small intestine (carcinoid, N=1). Noteworthy findings included: the frequent absence of a known primary tumor (62%), the rarity of bilateral involvement (8%), the occasional lack of a distinct mass on gross examination (15%), the infrequency of multinodularity either grossly (8%) or microscopically (35%), the prominence of intertubular growth (42%), conspicuous intrarete or intratubular growth in some cases (especially prostate carcinoma) (19%), prominent cytoplasmic vacuoles in occasional cases (15%), and the frequent presence of lymphatic involvement (69%). Four tumors (3 prostate, 1 renal) with prominent intrarete and/or intratubular growth had submitting diagnoses of either a primary rete neoplasm or seminoma. Four tumors (2 prostate, 1 renal, and 1 bladder) with prominently vacuolated pale cells simulated Sertoli cell tumor. We conclude that, if autopsy cases and incidental tumors in therapeutic orchiectomy specimens are excluded, metastatic carcinomas to the testis are usually solitary, unilateral tumors that may simulate primary neoplasms, including rete adenocarcinoma and Sertoli cell tumor. Despite the rarity of documented cases in the literature, the bladder and renal pelvis should not be overlooked as possible sources for testicular metastasis. The pathologist must have a high index of suspicion for the possibility of a metastatic carcinoma to the testis for any testicular tumor where the routine light microscopic or immunohistochemical findings are unusual for a primary neoplasm. Clues to the likely primary site can usually be gleaned from the pathologic findings.