Benign nodal lesions mimicking metastases from pediatric renal neoplasms: a report of the National Wilms' Tumor Study Pathology Center

Current concepts of ectopic nodal inclusions with special emphasis on nodal nevi

Nodal inclusions of ectopic tissue within lymph nodes are seen comparatively often in dermatopathology and general pathology. Glandular and nonglandular epithelium, as well as melanocytic nevi can be observed within lymph nodes and represent mostly incidental findings without any relevance. The main challenge in reporting these morphologic features is to differentiate such benign inclusions from metastatic settlements of distinct organ tumors. As sentinel node biopsy and lymph node dissection have become standard procedure in clinical oncology and have an immense clinical impact, the correct evaluation of these nodal inclusions is indispensable to avoid undertreatment or overtreatment of patients. In addition, the genesis of these inclusions has not yet been satisfactorily clarified. Two concepts have been laid out: the theory of benign metastases and the migration arrest theory. However, neither theory has so far been able to answer the following questions: Why do we find more nodal nevi in patients with melanoma who had a sentinel node biopsy than in patients without melanoma, and why do we not find nodal nevi in deep visceral lymph nodes? We present a comprehensive review of the current knowledge on nodal inclusions, proposing a concept for the pathogenesis of nodal nevi, to answer these questions.

Dataset for the reporting of nephrectomy specimens for Wilms' tumour treated with preoperative chemotherapy: recommendations from the International Society of Paediatric Oncology Renal Tumour Study Group

Datasets for histopathological reporting of many cancer types are developed by the International Collaboration on Cancer Reporting (ICCR), and are used in order to ensure standardised and uniformly accepted reporting as one of the essential requirements for comparison across patient populations in evaluating and validating pathological prognostic and predictive factors. Wilms' tumours are rare, and international reporting guidelines have not yet been published by the ICCR. The assessment of Wilms' tumours differs according to the treatment approach. The Children's Oncology Group, whose approach is followed mainly in North America, advocates primary surgery, and the International Society of Paediatric Oncology Renal Tumour Study Group (SIOP-RTSG), whose approach is followed in most countries around the world, uses preoperative chemotherapy as a first step, resulting in different subclassifications, staging criteria, and histopathological prognostic factors. This dataset is developed for the countries and institutions following the SIOP-RTSG approach, and it contains core (required) and non-core (recommended) elements, based on the results of the previous SIOP-RTSG studies, which are incorporated in the latest SIOP-RTSG UMBRELLA 2016 Study protocol. The core elements include clinical information, additional specimen submitted, macroscopic tumour site and appearance, tumour focality, tumour dimensions, macroscopic extent of invasion, block identification key, histological tumour type, histological tumour grade and risk group assessment, microscopic extent of invasion, lymphovascular invasion, resection margin status, regional lymph node status, histologically confirmed distant metastases, and pathological staging (SIOP staging system). The dataset should improve communication for patient care and prognostic determination of the old and new histopathological features.

The UMBRELLA SIOP-RTSG 2016 Wilms tumour pathology and molecular biology protocol

On the basis of the results of previous national and international trials and studies, the Renal Tumour Study Group of the International Society of Paediatric Oncology (SIOP-RTSG) has developed a new study protocol for paediatric renal tumours: the UMBRELLA SIOP-RTSG 2016 protocol (the UMBRELLA protocol). Currently, the overall outcomes of patients with Wilms tumour are excellent, but subgroups with poor prognosis and increased relapse rates still exist. The identification of these subgroups is of utmost importance to improve treatment stratification, which might lead to reduction of the direct and late effects of chemotherapy. The UMBRELLA protocol aims to validate new prognostic factors, such as blastemal tumour volume and molecular markers, to further improve outcome. To achieve this aim, large, international, high-quality databases are needed, which dictate optimization and international harmonization of specimen handling and comprehensive sampling of biological material, refine definitions and improve logistics for expert review. To promote broad implementation of the UMBRELLA protocol, the updated SIOP-RTSG pathology and molecular biology protocol for Wilms tumours has been outlined, which is a consensus from the SIOP-RTSG pathology panel.

Generalized lymphadenopathy secondary to isolated extramedullary hematopoiesis as an initial manifestation of primary myelofibrosis

Extramedullary hematopoiesis (EMH) is a presence of hematopoietic activity in the extramedullary sites. EMH can occur in both benign and malignant hematologic diseases. The liver and spleen are the most common sites, but may also occur infrequently at other sites. EMH often occurs in more than one site and quite rare in an isolated organ. In this study we describe an unusual case of generalized lymphadenopathy secondary to isolated extramedullary hematopoiesis as an initial manifestation of primary myelofibrosis. Computed tomography revealed generalized lymphadenopathy including mediastinal, abdominal and pelvic lymph nodes with extensive illdefined sclerotic lesions throughout the skeletal system suggestive of lymphoma/leukemia. Lymph node biopsy showed no evidence of malignancy or granuloma, however, large abnormal cells with multilobated nuclei were seen scattered in the lymph nodes. These abnormal cells were proved to be megakaryocytes. Granulocytic precursors were less obvious on the H&E section. The diagnosis was determined as EMH in the lymph node. Bone marrow (BM) examination showed hypercellular marrow for patient’s age with granulocytic and megakaryocytic proliferation with increase in BM fibrosis and reported as a myeloproliferative neoplasm, consistent with primary myelofibrosis. In summary, although EMH is not always a malignant process; it is important to stress that the patient should be investigated for underlying hematological disorders, when it is noted elsewhere.

VCL-ALK renal cell carcinoma in children with sickle-cell trait: the eighth sickle-cell nephropathy?

We report the third case of a renal cell carcinoma bearing a fusion of the vinculin (VCL) and anaplastic lymphoma kinase (ALK) genes. Like the 2 other reported cases, this neoplasm occurred in a young patient (6 y old) with sickle-cell trait and demonstrated distinctive morphologic features including medullary epicenter, discohesive polygonal or spindle-shaped cells with prominent cytoplasmic vacuoles, and prominent lymphocytic infiltrate. The neoplastic cells demonstrated focal membranous labeling for ALK protein by immunohistochemistry, ALK gene rearrangement by fluorescence in situ hybridization, and a specific VCL-ALK gene fusion by reverse transcriptase polymerase chain reaction. VCL-ALK renal cell carcinoma may represent the eighth sickle-cell nephropathy.

Local behavior and lymph node metastases of Wilms' tumor: accuracy of computed tomography

Objective To evaluate the accuracy of computed tomography for local and lymph node staging of Wilms' tumor. Materials and Methods Each case of Wilms' tumor was evaluated for the presence of abdominal lymph nodes by a radiologist. Signs of capsule and adjacent organ invasion were analyzed. Surgical and histopathological results were taken as the gold standard. Results Sensitivity was 100% for both mesenteric and retroperitoneal lymph nodes detection, and specificity was, respectively, 12% and 33%, with positive predictive value of 8% and 11% and negative predictive value of 100%. Signs of capsular invasion presented sensitivity of 87%, specificity of 77%, positive predictive value of 63% and negative predictive value of 93%. Signs of adjacent organ invasion presented sensitivity of 100%, specificity of 78%, positive predictive value of 37% and negative predictive value of 100%. Conclusion Computed tomography tumor showed low specificity and low positive predictive value in the detection of lymph node dissemination. The absence of detectable lymph nodes makes their presence unlikely, and likewise regarding the evaluation of local behavior of tumors.

Benign Salivary Gland Tissue Inclusion in a Pulmonary Hilar Lymph Node From a Patient With Invasive Well-Differentiated Adenocarcinoma of the Lung: A Potential Misinterpretation for the Staging of Carcinoma

Benign epithelial and nonepithelial inclusions have been found in lymph nodes in multiple body sites. These inclusions have been seen in cervical, axillary, mediastinal, abdominal, and pelvic lymph nodes. They appear as benign epithelial, parathyroid, decidual, mesothelial, angiolipomatous, nevus cells, or Tamm—Horsfall protein. Although heterotopic salivary gland tissue is not infrequent in paraparotid lymph nodes, it has only been described in lymph nodes of the pulmonary hilum once. A 68-year-old woman with gastric lymphoma now in remission presented for routine follow-up and was found to have a lung mass. After a fine needle aspiration biopsy diagnosis of adenocarcinoma, lobectomy and lymph node dissection were performed. Histological sections of lung demonstrated a well-differentiated adenocarcinoma and one lymph node, which displayed a subcapsular nest of well-formed salivary glands occupying approximately one third of the nodal tissue. The inclusion was composed of acinar cells of both serous and mucinous types, but ductal type of cells were not seen. Identification of heterotopic tissue in lymph nodes is of great importance for patient management. Misdiagnosing benign glandular inclusions for metastasis could potentially lead to incorrect tumor staging. Benign salivary gland tissue inclusions should be considered in the differential diagnosis when evaluating for metastatic adenocarcinoma. The salivary gland inclusion in pulmonary hilar lymph node may be histogenetically related to the minor salivary glands, which are located within the bronchial submucosa.

Renal tumours of childhood: an update

The role of the pathologist has been fundamental in the progress of the treatment of paediatric renal tumours. There are different philosophies in the treatment of these tumours, and there have been many recent advances in the areas of chemotherapy, identification of new entities, prognostic histological criteria following treatment and molecular prognostic and diagnostic features. This review discusses the different approaches of the different treatment protocols from Europe and North America, and reviews staging criteria, prognostic criteria and also the different tumour entities.

Mesothelial pelvic lymph node inclusion in a patient with ovarian microinvasive borderline mucinous tumor: case report with review of the literature

The presence of mesothelial cell inclusions in lymph nodes is rare. Localization of these inclusions in abdominal and pelvic lymph nodes is an exceedingly rare event, with only eight cases reported. We report here a case of mesothelial cell inclusions in pelvic lymph node of a patient with ovarian microinvasive borderline mucinous tumor. This case differs from the previously reported cases for the following reasons. First, there was no evidence of serosal effusion. Second, it is the first reported case of nodal mesothelial inclusions in a patient with ovarian microinvasive mucinous borderline tumor. Last, histologically, mesothelial cell inclusions were accompanied by psammoma bodies. The potential problem of misdiagnosis as a metastatic tumor can be avoided by an awareness of these inclusions, supported by immunohistochemical results.

Passive Seeding in Metanephric Adenoma: A Review of Pseudometastatic Lesions in Perinephric Lymph Nodes

Lymph node involvement derived from a discrete neoplastic process fundamentally implies tumor malignancy. However, rarely, inconsequential passive transport of benign neoplastic cells to the lymph node can occur and may cause confusion as to the nature of the neoplasm (ie, malignant vs benign). We describe a 10-cm right renal metanephric adenoma incidentally discovered in a 30-year-old woman during cesarean section for a triplet pregnancy. Subsequent nephrectomy following an equivocal needle biopsy diagnosis showed histologic features classic for metanephric adenoma, including the lack of cytologic atypia and mitoses. Necrosis present in this lesion appeared to be secondary to tumor physical disruption. The tumor cells were positive for Wilms tumor 1 (WT1) antigen, pankeratin, and CD57, focally positive for epithelial membrane antigen, and negative for cytokeratin 7, cytokeratin 34βE12, and CD56. Electron microscopy confirmed the tumor's epithelial nature, and cytogenetics revealed a diploid 46XX karyotype. The tumor proliferation index with Ki-67 was only 3% to 5% and the proliferating cell nuclear antigen index was 0%. A single, concurrently resected hilar lymph node contained scattered subcapsular, sinusoidal, and focally intralymphovascular psammoma bodies along with occasional adherent epithelial cells. These cells were highlighted by pankeratin but were nonreactive to WT1 antigen, similar to the nonviable cells in the primary tumor. Clinical surveillance and follow-up showed no disease recurrence 4 years after nephrectomy. We postulate that the lymph node inclusions found in this case represent passive transport of neoplastic cells to the lymph node following manipulation of the renal mass. We conclude that this phenomenon is understudied and underrecognized and can easily be mistaken for metastasis.

Pediatric renal tumors: practical updates for the pathologist

Pediatric renal tumors were targeted by the National Wilms Tumor Study Group for 4 decades with extraordinary success. Within this historic context, this review provides a summary of the new Children's Oncology Group renal tumor protocols that will be opening in the very near future, focusing on their pathologic requirements. All renal tumors must first be registered on the Renal Tumor Classification and Banking Protocol, followed by registration on 1 of 4 primary therapeutic protocols based on histology, stage, and molecular analysis. This requires prompt submission of samples for molecular analysis and central pathologic review. Changes in staging criteria include classification of all tumor spillage as stage III, and requirement of regional lymph node evaluation for eligibility for stage I Wilms tumors (WTs) weighing less than 550 g in infants younger than 24 months and for stage I clear cell sarcoma. Patients with unilateral favorable histology WT with loss of heterozygosity for chromosomes 1p and 16q will receive more aggressive chemotherapy at each stage. Patients with bilateral WT and patients with diffuse hyperplastic perilobar nephroblastomatosis will be eligible for a novel therapeutic protocol requiring pathologic classification based on response of tumor to previous therapy. Stage I anaplastic WT will be targeted with more aggressive chemotherapy than in the past. For the first time, pediatric renal cell carcinoma will be eligible for a cooperative group protocol. All rhabdoid tumors outside the central nervous system will be eligible for a single protocol. In conclusion, these new protocols bring considerable change in their overall organization, in eligibility, and in therapy.

Cellules épithéliales bénignes et protéine de Tamm-Horsfall dans les ganglions lymphatiques des pièces de néphrectomie pour néphroblastome : Un piège diagnostique

When a lymph node metastasis is discovered during the pathology examination of surgical specimens with nephroblastoma, the tumour is classified as stage III, according to the classification of the International Society of Paediatric Oncology (SIOP 2001), and post-operative intensive treatment of the patient includes irradiation and chemotherapy. Benign epithelial cells in perinephric lymph nodes in cases of renal tumours in childhood may be confused with metastases. They are often associated with an accumulation of Tamm-Horsfall protein in lymph node sinuses. This case illustrates latero-aortic lymph node complexes of benign epithelial cells and Tamm-Horsfall protein in a 16-month-old girl with surgical resection of a nephroblastoma after pre-operative chemotherapy. The nephroblastoma was predominantly epithelial and was classified as SIOP stage I. There were accumulations of Tamm-Horsfall protein in lymph node sinuses, in lymphatic vessels, in the kidney outside the tumour, and in the renal sinus. This association of epithelial cells with deposits of Tamm-Horsfall protein and their resemblance to cells of the distal convoluted tubules favour a diagnosis of benignity. A definitive diagnosis is supported by the small size of the cells, their bland nuclei, and morphological features differing from those of tumour cells, but deposits of Tamm-Horsfall protein may be associated with true lymph node metastases.

Megakaryocytes mimicking metastatic breast carcinoma

False-positive diagnosis of lymph nodes occurs when a benign element in a lymph node, or in its capsule, is interpreted as metastatic carcinoma. This report describes a patient with breast carcinoma who had megakaryocytes in axillary sentinel lymph nodes mimicking metastatic carcinoma. The patient had no history of a hematologic disease, and we found no evidence of a concurrent hematopoietic disorder. The megakaryocytes were reactive for CD31, CD61, and von Willebrand factor, but not for cytokeratin (AE1/AE3). Megakaryocytes should be added to the list of benign histologic abnormalities that may simulate metastatic carcinoma in a sentinel lymph node.

Hyperplastic mesothelial cells in mediastinal lymph node sinuses with extranodal lymphatic involvement

We describe a patient with hyperplastic mesothelial cells localized to mediastinal lymph node sinuses. These mesothelial cells were originally misdiagnosed as metastatic carcinoma, and the patient received radiotherapy. Histologic review, immunohistochemistry, and ultrastructural studies confirmed mesothelial cell origin. These nodal mesothelial cells were associated with pericardial and pleural effusions. Extranodal lymphatics also contained hyperplastic mesothelial cells, confirming their mode of lymphatic transport to node sinuses. This finding supports the theory that hyperplastic mesothelial cells derive from reactive serosal mesothelium and are dislodged into draining lymphatics. This is the first report, to our knowledge, that demonstrates the pathogenetic significance of this lymphatic transport mechanism. Awareness of intralymphatic and nodal benign hyperplastic mesothelial cells and their mimicry of invasive malignant neoplasms is important for accurate diagnoses and appropriate therapy.

Benign transport of breast epithelium into axillary lymph nodes after biopsy

The most important prognostic indicator of distant metastasis in breast cancer is histologic documentation of axillary lymph node metastasis. Controversy exists about the importance of micrometastases (< 0.2 cm), and current pathology practice includes a careful search for their presence. We describe the histologic findings in a series of axillary lymph node dissections taken approximately 2 weeks after breast biopsy. Each case has limited presence of epithelial cells in the subcapsular sinus of a draining lymph node that we attribute to mechanical transport of tumor and/or normal breast epithelium secondary to the previous surgical or needle manipulation. These cells were accompanied by hemosiderin-laden macrophages and damaged RBCs. While the clinical implication of these findings is unknown, we believe that it will be of no clinical significance and have no untoward prognostic effect.

Benign mesothelial cells in mediastinal lymph nodes

Inclusions of benign tissues in lymph nodes are most often aberrant glandular tissue, including endosalpingiosis, the thyroid, parotid, breast, and pancreas. Nonglandular inclusions are rare and include nevus cells and decidua. Mesothelial cells in lymph nodes are exceedingly rare; only eight cases have been reported in mediastinal lymph nodes and three cases in abdominal lymph nodes. The incidence of benign mesothelial cells in mediastinal lymph nodes in patients with a history of pericarditis or pleuritis is reported in this study. A retrospective search showed eight cases with removal of mediastinal lymph nodes in the absence of neoplasm. Hematoxylin and eosin-stained sections were examined in all cases. Immunohistochemical stains for CAM 5.2 were performed in all cases, and stains for AE1/AE3, Ber-EP4, carcinoembryonic antigen, Leu-M1, B72.3, and S-100 were performed in one case. CAM 5.2-positive cells with features of mesothelial cells were present in five of eight cases. In all cases, the cells were present in nodal sinuses and appeared as single cells or small clusters. The cells were missed on routine hematoxylin and eosin sections in all cases but one, in which they were numerous and mimicked metastatic carcinoma. Malignancy was not found in any of the cases preoperatively, at the time of surgery, or during the follow-up period. Benign mesothelial cells may embolize to regional lymph nodes in pleuritis or pericarditis. In most cases, these cells are few and undetectable on routine sections. Rarely, hyperplastic mesothelial cells may be present and must be distinguished from metastatic carcinoma, mesothelioma, and melanoma.

Hyperplastic mesothelial cells in lymph nodes: report of six cases of a benign process that can stimulate metastatic involvement by mesothelioma or carcinoma

We report six cases of hyperplastic mesothelial cells located in the sinuses of lymph nodes. All patients but one had a concurrent serosal fluid collection (two pericardial, two pleural, one abdominal) at the time of the lymph node biopsy. All effusions cleared with treatment of the underlying disorder, which included lymphoproliferative processes, congestive heart failure, and inflammatory diseases (Dressler syndrome, vasculitis, and glomerulonephritis). Four cases were associated with vascular prominence of the involved nodal sinuses, a feature that may reflect the cause of the underlying effusion or support the transient persistence of benign mesothelial cells in lymph nodes. Two cases were characterized by distention of the nodal sinuses by sheets of mitotically active mesothelial cells. The differential diagnosis includes metastatic carcinoma, keratin-positive dendritic cells native to lymph nodes, and metastatic malignant mesothelioma. Because the latter shares both clinical and morphological features with cases of benign mesothelial cells in lymph nodes, we believe that this distinction may not always be possible in a given biopsy specimen and therefore that careful clinical follow-up is required in such cases.

Mesothelial cell inclusions within mediastinal lymph nodes

The presence of mesothelial cell inclusions within mediastinal lymph nodes is an extremely rare occurrence with apparently only two previously reported cases. We report a single case with immunohistochemistry and transmission electron microscopy. A study of 318 mediastinal nodes from 80 patients using haematoxylin and eosin and immunohistochemistry is reported with the observation of no further positive cases. A review of the literature concerning nodal inclusions found at other anatomical sites aids discussion on the aetiology of this type of nodal inclusion.

renal tumors and tumor-like lesions in pediatric patients

Renal enlargement presenting as an abdominal mass(es) is attended by a lengthly differential diagnosis of non-neoplastic and neoplastic lesions with a range in serious connotations and consequences. Simple compensatory hypertrophy and unilateral multicystic dysplasia are relatively innocuous and easily recognized with appropriate imaging studies; they are also related in the sense that the normal contralateral kidney hypertrophies in the absence of a non-functioning dysplastic kidney. Bilateral nephromegaly in a neonate is generally a sign of autosomal recessive polycystic kidney disease or multicystic dysplasia secondary to distal obstructive uropathy. Primary neoplasms of kidney in the pediatric population in the past were traditionally classified as Wilms' tumors, but that erroneous practice has been eliminated with the recognition of several distinctive neoplasms in addition to classic Wilms' tumor. Separating a typical Wilms' tumor from mesoblastic nephroma, clear cell sarcoma of the kidney and the malignant rhabdoid tumor, for treatment and prognostic purposes, has become the accepted norm in the past 12-13 years. Another important advance at the cellular level is the recognition of a deletion in the short arm of chromosome 11 in the cultured cells of Wilms' tumor and in the germ cell line in certain clinical settings of Wilms' tumors. A dramatic expansion in the understanding and management of childhood renal neoplasms has occurred through the multimodality approach of laboratory investigation and applied clinical research.