Spindle cell lesions of the adult prostate.

Prostatic spindle cell lesions are diagnostically challenging and encompass a broad array of benign and malignant processes. A subset of these lesions arises only within the prostate and generally represents entities that originate from the prostate epithelium or stroma, such as sclerosing adenosis, sarcomatoid carcinoma, stromal tumors of uncertain malignant potential (STUMP), and stromal sarcoma. Another subset of spindle cell tumors that involve the prostate are also found at other sites and include solitary fibrous tumor, leiomyosarcoma, and neural lesions among others. Finally, tumors may secondarily involve the prostate yet present as primary prostatic processes, as is evident with several cases of gastrointestinal stromal tumors (GIST). The utility of ancillary studies, including immunohistochemistry, is often limited and the main criteria for diagnosis are the morphologic findings by routine H&E stain. This review addresses the various entities that may present as spindle cell tumors within the adult prostate and discusses the functional aspects of the differential diagnosis of these lesions.     

STAT6 expression in spindle cell lesions of the breast: An immunohistochemical study of 48 cases

The diagnosis of spindle cell lesions of the breast parenchyma is challenging. Some of these lesions share the expression of CD34, posing differential diagnostic problems, especially in core biopsies. Recently, antibodies against the STAT6 C-terminal, are being used in paraffin-embedded tissues as a surrogate for identifying the NAB2–STA6 fusion gene which is considered a specific molecular marker for solitary fibrous tumor. Accordingly, we investigated the expression of STAT6 in a large series of uncommon spindle cell tumor-like and tumor lesions occurring primarily in the breast parenchyma. We collected 10 classic-type myofibroblastomas, 9 desmoid-type fibromatosis, 6 spindle cell metaplastic carcinoma, 5 benign fibroblastic spindle cell tumors, 3 solitary fibrous tumors, 7 pseudoangiomatous stromal hyperplasias, 2 reactive spindle cell nodules, 1 leiomyoma, 1 spindle cell lipoma, 1 case of inflammatory pseudotumor, 1 nodular fasciitis, 1 myxoma and 1 dermatofibrosarcoma protuberans. A diffuse and strong nuclear STAT6 expression was restricted only to solitary fibrous tumors, while the other lesions were negative or showed only weak cytoplasmic expression. The present study confirms that the demonstration of a diffuse and strong STAT6 nuclear staining is very helpful in distinguishing solitary fibrous tumor from other spindle cell mimics arising in the breast.     

低度恶性中央性骨肉瘤的病理诊断与鉴别诊断

目的 探讨低度恶性中央性骨肉瘤(LGCOS)诊断与鉴别诊断要点.方法 收集9例LGCOS(均为会诊病例),对其临床、病理组织学和影像学进行观察和分析,并复习相关文献.结果 临床特点:9例患者中男性3例,女性6例,平均年龄约31岁.影像学均表现为成骨和溶骨混合性骨质破坏,边界不清,5例伴软组织影,3例有骨膜反应.9例均有局部疼痛和(或)肿胀,4例发生在股骨,胫骨、腓骨、颈椎、腰椎、上颌骨各1例.均行手术切除,术后未予放疗等辅助治疗,随访时间2～43个月,其中4例分别于术后25、18、8和13个月复发.病理检查:(1)大体检查:5例为碎组织,4例为块状切除标本,切面质地较韧,有不同程度的沙砾感,均无鱼肉样外观.(2)镜下观察:肿瘤由两种基本成分,即纤维成分和新生编织骨;纤维细胞密度较低,轻度异形,9例中均查见个别核分裂象;新生骨小梁均为编织骨,6例骨小梁宽大,有平行排列倾向,3例骨小梁较小,骨小梁周边均缺乏骨母细胞围绕;纤维成分和编织骨比例不一,两种成分有移行现象.病变呈浸润性生长,9例均有髓腔侵犯,3例伴有邻近软组织侵犯.结论 LGCOS细胞异形不明显、肿瘤性骨小梁较宽大成熟,易漏诊,诊断时应充分做到临床、影像学和病理三结合.临床特点:病程较长,局部缺少特征性表现.影像学:成骨和溶骨混合性病变,边界不清,骨皮质破坏或伴有邻近软组织影.病理形态:大体上缺少鱼肉样外观;镜下肿瘤性纤维成分轻度异形,可见核分裂象,肿瘤性骨小梁周边缺乏骨母细胞围绕,有平行排列倾向,纤维性成分和新生骨型小梁有直接移行现象;病变呈浸润性生长.     

低度恶性中央性骨肉瘤的病理诊断与鉴别诊断

目的 探讨低度恶性中央性骨肉瘤(LGCOS)诊断与鉴别诊断要点.方法 收集9例LGCOS(均为会诊病例),对其临床、病理组织学和影像学进行观察和分析,并复习相关文献.结果 临床特点:9例患者中男性3例,女性6例,平均年龄约31岁.影像学均表现为成骨和溶骨混合性骨质破坏,边界不清,5例伴软组织影,3例有骨膜反应.9例均有局部疼痛和(或)肿胀,4例发生在股骨,胫骨、腓骨、颈椎、腰椎、上颌骨各1例.均行手术切除,术后未予放疗等辅助治疗,随访时间2～43个月,其中4例分别于术后25、18、8和13个月复发.病理检查:(1)大体检查:5例为碎组织,4例为块状切除标本,切面质地较韧,有不同程度的沙砾感,均无鱼肉样外观.(2)镜下观察:肿瘤由两种基本成分,即纤维成分和新生编织骨;纤维细胞密度较低,轻度异形,9例中均查见个别核分裂象;新生骨小梁均为编织骨,6例骨小梁宽大,有平行排列倾向,3例骨小梁较小,骨小梁周边均缺乏骨母细胞围绕;纤维成分和编织骨比例不一,两种成分有移行现象.病变呈浸润性生长,9例均有髓腔侵犯,3例伴有邻近软组织侵犯.结论 LGCOS细胞异形不明显、肿瘤性骨小梁较宽大成熟,易漏诊,诊断时应充分做到临床、影像学和病理三结合.临床特点:病程较长,局部缺少特征性表现.影像学:成骨和溶骨混合性病变,边界不清,骨皮质破坏或伴有邻近软组织影.病理形态:大体上缺少鱼肉样外观;镜下肿瘤性纤维成分轻度异形,可见核分裂象,肿瘤性骨小梁周边缺乏骨母细胞围绕,有平行排列倾向,纤维性成分和新生骨型小梁有直接移行现象;病变呈浸润性生长.     

Immunohistochemical expression of HBME-1 and galectin-3 in the differential diagnosis of follicular-derived thyroid nodules

BackgroundThyroid nodules are common among adults with only a small percentage being malignant and histologically mimic benign nodules. Accurate diagnosis of these thyroid nodules is critical for the proper clinical management. The determination of malignancy in follicular patterned thyroid lesions is based on postoperative histological findings. Therefore, affected patients are referred for surgery, although only 10% will have a final diagnosis of malignancy. The aim of this study was to investigate the ability of two immunohistochemical (IHC) markers; galectin-3 and Hector Battifora mesothelial-1 (HBME-1) individually or in combination, to distinguish between benign (non-neoplastic and neoplastic) and malignant (follicular and papillary carcinomas) thyroid lesions removed by surgical resection.MethodsWe investigated the immunoexpression of galectin-3 and HBME-1 in 50 cases of benign and malignant thyroid nodules. The benign group included 13 cases of thyroid nodular goiter (NG) and 9 cases of follicular adenoma (FA). The malignant group included 5 cases of follicular thyroid carcinomas (FC), 18 cases of classic papillary thyroid carcinoma and 5 cases of follicular variant papillary carcinoma (FVPC).ResultsThe staining results showed that malignant tumors expressed galectin-3 and HBME-1 significantly more than benign nodules. The sensitivity of these markers for the distinction between benign and malignant lesions ranged from 89.3% to 92.9%. Co-expression of galectin-3 and HBME-1 was seen in 82.1% of carcinomas, but in none of the benign nodules. Immunoexpression was usually diffuse in malignant tumors, and focal in the benign lesions.ConclusionOur findings indicate that these immunohistochemical markers are significantly more expressed in malignant tumors compared to benign lesions and may be of additional diagnostic value when combined with routine histology. Galectin-3 has higher sensitivity and specificity of immunoexpression in thyroid malignancy than HBME-1, and the combined use of galectin-3 and HBME-1 can increase the specificity of immunoexpression in malignant tumors.     

What do we know about inflammatory myofibroblastic tumors? – A systematic review

BackgroundInflammatory myofibroblastic tumors (IMTs) are rare intermediate-grade neoplasms that have a high recurrence rate after excision and exhibit low metastatic potential. These tumors contain proliferating neoplastic, fibroblastic and myofibroblastic cells, and are also characterized by chronic inflammatory infiltration by lymphocytes, plasma cells, eosinophils, and histiocytes. They belong to the group of inflammatory spindle cell lesions. Some reactive lesions, such as inflammatory pseudotumors, may appear to be IMTs, which makes their differential diagnosis extremely difficult. The aim of this article is to compile the recent information on IMTs to aid in their diagnosis and treatment.MethodsWe reviewed articles published between 2017 and 2021, which were selected from online medical databases. In addition, some earlier articles and latest scientific monographies were analyzed.ResultsThe terminology used for inflammatory spindle cell lesions seems to be confusing. The terms “inflammatory myofibroblastic tumors” and “inflammatory pseudotumors” are interchangeably used by many scientists. However, a detailed analysis of the development of terminology suggests that the term “inflammatory myofibroblastic tumors” should be used to refer to a neoplastic lesion.ConclusionsIMTs are rare neoplasms, which have not been investigated in detail due to the difficulty in collecting a large number of cases. Thus, our knowledge about this disease remains unsatisfactory. Recently developed techniques such as next-generation sequencing and computer-aided histopathological diagnosis may be useful in understanding the etiopathology of IMTs, which will help in the selection of the most appropriate therapy for patients.     

Epiphyseal osteosarcoma revisited: four illustrative cases with unusual histopathology and literature review

Osteosarcomas arising in the epiphysis are extremely rare and easily missed in the diagnostic consideration of epiphyseal tumors. It is the purpose of this study to delineate the clinical pathological characteristics of ‘epiphyseal osteosarcoma’ under the definition of ‘a solitary long bone osteosarcoma radiographically considered an epiphyseal tumor for which the main radiologic differential diagnosis would encompass giant cell tumor, chondroblastoma and clear cell chondrosarcoma’. Four such cases with unusual histopathology were retrieved among 110 cases of osteosarcoma. Their clinical, radiological and pathological features, together with all 10 reported cases, were analyzed. The radiographic diagnoses of our four cases include two giant cell tumors, one chondroblastoma and one clear cell chondrosarcoma but turn out to be fibroblastic, giant cell rich, telangiectatic and epithelioid variant of epiphyseal osteosarcoma. Including our patients, the 14 reported epiphyseal osteosarcomas comprise 8 males and 6 females, the age at presentation ranges from 11 to 39 years, two‐third in the second decade, 71.4% affect the femur. Due to their epiphyseal locations, many carry benign radiological diagnoses notably giant cell tumor and chondroblastoma. Epiphyseal osteosarcomas may not only masquerade as benign radiological bony lesions but also assume many histological patterns; orthopedic surgeons, radiologists and pathologists should be aware of such possibility. Their behavior and prognosis are dictated by the histologic types, grading and staging rather than location.     

Non-neoplastic nodular lesions in the liver

The classical nomenclature and categorization of neoplastic and non-neoplastic nodular lesions of the liver are being revised due to the tremendous volume of information recently published on this issue. The diagnostic histopathology of non-neoplastic nodular (tumor-like) lesions of the liver that are recognizable in biopsied, surgically resected and autop sied livers is reviewed using current terminology. Generally, such nodules are infrequent and even rare in routine liver specimens. Non-neoplastic nodules include focal nodular hyperplasia, nodular regenerative hyperplasia, compensatory hyperplasia of the liver, pseudonodule of the liver demonstrable by angiography, partial nodular transformation, focal fatty change, nodular hepatic area shown by modified angiography, cirrhotic large regenerative nodule with variable atypia, anoxic pseudolobular necrosis, intrahepatic bile duct adenoma, biliary and mesenchymal hamartoma, and mesenchymal nodular lesions such as inflammatory pseu-dotumor and pseudolymphoma, pseudolipoma, peliosis hepatis, solitary necrotic nodule, and so on. Some of these develop preferentially in non-cirrhotic or cirrhotic livers, while others occur with similar prevalence in cirrhotic and non-cirrhotic livers. Some occur multiply or diffusely and others singly. As to the pathogenesis of these nodules, it is speculated that hyperplasia due to disturbed intrahepatic circulation or hormonal imbalance, preneoplastic characteristics, abnormal metabolic disturbance, hamartoma or focal necrobiotic processes, and infection have a role. Knowledge and awareness of these non-neoplastic nodular lesions are necessary for precise diagnosis and differentiation of these nodular lesions from neoplastic hepatic nodules.     

Nonepithelial tumor-like lesions of the prostate: a never-ending diagnostic problem

Nonepithelial tumor-like lesions of the prostate include benign prostatic hyperplasia-associated stromal nodules, postoperative spindle cell nodules, benign mesenchymal tumors and sarcomas. These lesions and neoplasms are rare but need to be exactly classified for adequate treatment. This review focuses on the differential diagnosis between the various benign and malignant entities and compares the new WHO classification with a recently published typing of prostatic stromal lesions of unknown malignant potential.     

The role of radiological-pathological correlation in diagnosing early breast cancer: the pathologist's perspective

Early breast carcinoma, defined as purely in situ cancer and invasive carcinomas < 15 mm, represents the most frequent category of breast carcinomas in diagnostic routine in a regularly screened population. These tumors are usually detected with mammography screening and are preoperatively characterized with radiological imaging. The role of pathology in preoperative settings is to help understand the subgross morphology and to confirm malignancy in biopsy material. Postoperatively, the pathologist needs to verify the size of the cancer (defined as the largest dimension of the largest invasive focus), the extent of the disease (defined as the area or the volume of the breast tissue containing all the malignant foci), the distribution of the in situ and invasive lesions (as unifocal, multifocal, or diffuse), and intratumoral and intertumoral heterogeneity (in addition to determining margin status, histologic tumor type, hormone receptor status, and other parameters). Despite their small size, early breast carcinomas often exhibit complex morphology as they are multifocal/diffuse in about 60% and extensive (occupying an area ≥ 4 cm) in 40% of the cases. Routine use of large-format histopathology technique is a prerequisite for detailed correlation of the radiologic and histopathologic findings and for the correct assessment of these parameters. Breast pathologists must be aware of the advantages and disadvantages of the different imaging modalities and have detailed information about the radiological findings before work-up of the operative specimen. Multidisciplinary preoperative and postoperative tumor board meetings are essential in guiding the pathologists and in confirming the radiological findings. Interdisciplinary diagnosis is inevitably becoming the new gold standard in the diagnosis and management of early breast carcinomas.     

Benign spindle cell tumors of the mammary stroma: diagnostic criteria, classification, and histogenesis

Purely benign mesenchymal spindle cell neoplasms of the breast are currently labeled under various terms in the literature (benign spindle cell tumor, fibroma, spindle cell lipoma, myofibroblastoma, solitary fibrous tumor, myogenic stromal tumor). The lack of strict diagnostic criteria to clearly indicate such mesenchymal neoplasms is the main reason which generated the risk of terming the same lesion under different names or, conversely, of collecting different types under the same term. Although such neoplasms exhibit morphological and immunophenotypical heterogeneity, they actually represent variations of the same tumor entity, likely arising from the uncommitted vimentin+/CD34+ fibroblasts of the mammary stroma, capable of multidirectional mesenchymal differentiation. To cover the entire spectrum of such lesions, the term "benign spindle cell tumors (BSCTs) of the mammary stroma" is advocated. BSCTs can be subtyped into four main groups by light microscopy (LM) and immunocytochemistry (ICC): fibroblastic, myofibroblastic, fibrohistiocytic, and mixed forms. A simple and practical approach to a nosologically correct diagnosis and a list of differential diagnoses are presented. The awareness of the diversity of morphological and immunophenotypical features of BSCTs of the mammary stroma, including uncommon variants, is helpful to avoid confusion with other monomorphic bland-looking benign and malignant spindle cell tumors and tumor-like lesions of the breast.     

Usefulness of immunohistochemistry as a diagnostic tool for tumors and pseudotumoral bone lesions

Immunohistochemical study for the diagnosis of bone tumors and tumor-like lesions has to be scheduled after an appropriate analysis of clinical data, radiological findings, and results of histology in H-E sections. The value of several markers for osteoblasts is discussed, chiefly for various forms of osteosarcomas. In the same way, the role of S-100 protein as well as anticollagen type II antibody is developed for cartilaginous tumors. The selection of markers in the fields of round cell tumors and spindle cell tumors of bone is also discussed. Some diagnostic problems with the support of immunohistochemistry are described, like chordomas versus chondrosarcomas or bone metastases. Lastly, immunohistochemical study of proliferating factors in the bone tumor field is quoted.     

超声对睾丸肿瘤及肿瘤样病变的诊断及鉴别诊断

目的 探讨超声对睾丸肿瘤及肿瘤样病变的诊断及鉴别诊断价值.方法 回顾分析33例睾丸肿块患者的超声声像图表现,并与其病理结果进行对照.结果 33例睾丸肿块患者中,精原细胞瘤12例,淋巴瘤6例,表皮样囊肿6例,混合性生殖细胞瘤2例,畸胎瘤2例,胚胎性癌、内胚窦瘤各1例,其他3例.结论 超声检查对睾丸肿瘤及肿瘤样病变的诊断及鉴别诊断具有重要价值,可为进一步治疗方案的制定提供依据,是睾丸肿瘤首选的影像学检查方法.     

Incompletely differentiated (unclassified) sex cord/gonadal stromal tumor of the testis with a "pure" spindle cell component: report of a case with diagnostic and histogenetic considerations

The group of incompletely differentiated (unclassified) sex cord/gonadal stromal tumors includes rare cases with predominant spindle cell morphology. We report a rare case of a "pure" spindle cell tumor of the testis with morphological and immunohistochemical features consistent with the diagnosis of "incompletely differentiated sex cord/gonadal stromal tumor". Given the spindle cell morphology, the differential diagnosis with other benign and malignant spindle cell lesions is discussed. The concurrent presence of some morphological and immunohistochemical features of both Leydig and granulosa cell lines in the tumor suggests its origin from a stromal stem cell, possibly capable of dual differentiation, but with an arrest of maturation at an early phase of differentiation.     

Reliability of fine-needle aspiration biopsy in the initial diagnosis of soft-tissue lesions

We retrospectively reviewed fine-needle aspiration biopsy (FNAB) specimens of 301 soft tissue lesions of the extremities and trunk. Final diagnoses were 137 benign and 86 malignant neoplasms and 78 nonneoplastic lesions. Of the 301 FNAB samples, 279 (93%) were adequate for cytologic diagnosis. The adequate FNAB specimens were initially grouped into three broad categories: benign (197 cases), malignant (57 cases), and suspicious for malignancy (25 cases). Sensitivity and specificity for diagnosis of a malignant lesion were 92% and 97%, respectively. The specimens were cytomorphologically classified into nine categories: small round (14 cases), spindle cell (77 cases), epithelioid/polygonal (16 cases), pleomorphic (29 cases), myxoid (19 cases), lipomatous (37 cases), epithelial (23 cases), inflammatory lesions (28 cases), and others (36 cases). Specific FNAB diagnoses were correct in 151 of 279 cases (54%) in combination with clinical and radiologic findings. FNAB is a valuable technique for the primary diagnosis of soft-tissue lesions.     

Primary pulmonary meningiomas: report of two cases and review of the literature

BackgroundMeningiomas rarely occur outside the skull, and primary pulmonary meningiomas (PPMs) are more rare. Only a few cases have been reported in the literature. The clinicopathological characteristics are not clear and it is easy to be misdiagnosed, so it is very important to master its diagnosis and differential diagnosis.MethodsWe report two women with primary pulmonary meningioma. At the time of physical examination, the small solitary pulmonary nodules were detected on chest radiograph, and wedge resection was performed by Video-assisted Thoracoscope Surgery(VATS), and histologic evaluation showed that the lesions were benign PPMs. The clinicopathological features, immunophenotype and differential diagnosis of PPMs were analyzed, with a review of the cases published in the literature.ResultsThe study group comprised of 40 patients, 14 males and 26 females. The median age was 56.5 years (range 18–108). Thirty patients who underwent routine screening studies were asymptomatic but had a pulmonary nodule detected on chest X-ray. Nine patients had respiratory symptoms. Only 1 patient had non-specific symptoms. Most of the PPMs were benign, only 3 cases were malignant. Benign PPMs ranged from 0.6 cm to 6 cm in diameter (median 2 cm). The 3 malignant PPMs were 5 cm, 6.5 cm and 15 cm in diameter. The prognosis of benign PPM resection is good, with almost no recurrence or metastasis. But the two of three malignant PPMs relapsed.ConclusionsPPM is very rare. It needs to be diagnosed by combining histology and immunohistochemistry. Diseases that need to be identified include spindle cell mesothelioma, spindle cell thymoma, spindle cell carcinoma, metastatic tumor, etc.     

Differential diagnosis of ovarian tumors based primarily on their patterns and cell types

The differential diagnosis of ovarian tumors is reviewed based on their patterns and cell types. This approach, which differs from the standard textbook discussion of each neoplasm as an entity, has practical value as differential diagnosis depends largely on the pattern or patterns and cell type or types of tumors. Awareness of the broad range of lesions that may exhibit particular patterns or contain one or more cell types is crucial in formulating a differential diagnosis. The following patterns are considered: moderate-to-large-glandular and hollow-tubular; solid tubular and pseudotubular; cords and ribbons; insular; trabecular; slit-like and reticular spaces; microglandular and microfollicular; macrofollicular and pseudomacrofollicular; papillary; diffuse; fibromatous-thecomatous; and biphasic and pseudobiphasic. The following cell types are considered: small round cells; spindle cells; mucinous cells, comprising columnar, goblet cell and signet ring cell subtypes; clear cells; hobnail cells; oxyphil cells; and transitional cells. The morphologic diversity of ovarian tumors poses many challenges; knowledge of the occurrence and frequency of these patterns and cell types in various tumors and tumor-like lesions is of paramount diagnostic importance. A specific diagnosis can usually be made by evaluating routinely stained slides, but much less often, special staining, immunohistochemical staining or, very rarely, ultrastructural examination is also required. Finally, clinical data, operative findings, and gross features of the lesions may provide important, and at times decisive diagnostic clues.     

Interpretation of core biopsy of liver mass lesions: A comparison study between cytopathologist and gastrointestinal pathologist

ContextCore biopsy (CB) is a main tool for diagnosis of liver mass lesions. When CB is performed with fine needle aspiration (FNA), the CB may be interpreted by a cytopathologist or gastrointestinal pathologist.ObjectiveThis study compares interpretation of liver mass biopsy between cytopathologist and gastrointestinal pathologist in the era of subspecialty practice.Design349 liver mass lesions with FNA and CB performed during a 5-year period were retrieved. All cases were initially interpreted by a cytopathologist and retrospectively reviewed by a gastrointestinal pathologist.ResultsThe overall agreement was 95.1% (332/349 cases). There was agreement on 57/65 non-neoplastic cases (87.7%) with 8 (12.3%) discordant cases including 4 steatosis (steatohepatitis missed in 3 cases, 1 re-interpreted as focal nodular hyperplasia [FNH]); 3 inflammation (1 necrotizing granulomatous inflammation, 1 massive necrosis instead of fibrosing cholestatic hepatitis, and 1 hepatocellular carcinoma [HCC] was missed); and 1 initially deemed normal re-interpreted as FNH. There was agreement on 275/284 neoplastic cases (96.8%), with 9 (3.2%) discordant cases including: 2 initially interpreted as HCC (1 metastatic adrenal cortical carcinoma, 1 cholangiocarcinoma); 3 adenocarcinomas (2 further defined as prostatic primary, 1 well-differentiated neuroendocrine tumor [WDNET]); 2 metastatic carcinomas (1 tumor-induced fibrosis instead of cirrhosis, 1 LCNEC re-interpreted as WDNET); 1 poorly differentiated carcinoma (re-interpreted as LCNEC); and 1 sarcomatoid carcinoma (re-interpreted as leiomyosarcoma).ConclusionCytopathologist and gastrointestinal pathologist are highly concordant in the interpretation of neoplastic liver mass CB. Consultation may improve accuracy in certain non-neoplastic biopsies and neuroendocrine neoplasms.     

Audit of tumour histopathology reviewed by a regional oncology centre.

AIMS--To analyse the diagnostic differences in reporting tumour histopathology between a district general hospital and a regional oncology centre. METHODS--Tumour histopathology reports (n = 227) extracted from Bolton General Hospital files between 1988 and 1992 were compared with the corresponding Christie Hospital (oncology centre) reports, the same material having been seen at both hospitals. RESULTS--Diagnostic agreement existed in 77% of all cases. The incidence of major discrepancies was 8.37%. Of the diagnoses, 19 (36%) cases involved major discrepancies and 34 (64%) cases minor discrepancies. Most discrepancies occurred in the lymphoma group and involved subclassification of Hodgkin''s and non-Hodgkin''s lymphoma. Ki1 anaplastic large cell lymphoma and T cell rich B cell lymphoma were problematic diagnoses. The correct grading of follicle centre cell lymphomas using the Kiel classification was another problem area. In 19 cases certain aspects of immunohistochemistry produced discrepancies. In one case an incorrect diagnosis was made at the oncology centre and in another both centres gave an incorrect diagnosis. CONCLUSIONS--Areas of diagnostic difficulty mainly involve the subclassification of lymphomas. Review of tumour pathology by experts is recommended, at least in certain categories, to ensure correct diagnosis and uniformity in subclassification of tumours.