Tubulocystic Carcinoma, Mucinous Tubular and Spindle Cell Carcinoma, and Other Recently Described Rare Renal Tumors

The Histologic Diversity of Chromophobe Renal Cell Carcinoma With Emphasis on Challenges Encountered in Daily Practice

Chromophobe renal cell carcinoma (ChRCC) is the third most common renal cell carcinoma in adults. The aim of this review is to provide a comprehensive overview highlighting the broad morphologic spectrum of ChRCC, and offer a practical approach for handling cases in daily practice. For the purpose of this review, we classify ChRCC subtypes as (1) classic, (2) eosinophilic, (3) sarcomatoid, and (4) other rare patterns. The concept of eosinophilic ChRCC has significantly evolved, yet it still is one of the major diagnostic challenges pathologists face in routine practice due to its morphologic overlap with renal oncocytoma. Rare patterns of ChRCC have been described over the last few decades, showing a wide histologic spectrum including those with adenomatoid microcystic pigmented, multicystic, neuroendocrine, small cell, and papillary features. ChRCC represents a heterogenous group of neoplasms, demonstrating varied but unique morphologic and genetic profiles. Although the field of ChRCC knowledge is still evolving, rare patterns can present diagnostic challenges if they are not known to pathologists and/or clinicians. Proper and generous tumor sampling along with careful histologic examination allow for recognition of these rare morphologies. The role of routine molecular testing appears to be limited. From a clinical management standpoint, the rare patterns of ChRCC seem to have no definite clinical implications at present and likely can be managed similarly to usual ChRCC. Finally, we will discuss distinctive novel/emerging renal neoplasms previously considered under the spectrum of ChRCC, low-grade oncocytic renal tumor and eosinophilic vacuolated tumor, with regard to their current significance and implications for future classification strategies.

Advances in neuroendocrine prostate cancer research: From model construction to molecular network analyses

Prostate cancer is the most common cancer among men and has a high incidence and associated mortality worldwide. It is an androgen-driven disease in which tumor growth is triggered via ligand-mediated signaling through the androgen receptor (AR). Recent evidence suggests that the widespread use of effective AR pathway inhibitors may increase the occurrence of neuroendocrine prostate cancer (NEPC), an aggressive and treatment-resistant AR-negative variant; however, mechanisms controlling NEPC development remain to be elucidated. Various preclinical models have recently been developed to investigate the mechanisms driving the NEPC differentiation. In the present study, we summarized strategies for the development of NEPC models and proposed a novel method for model evaluation, which will help in the timely and accurate identification of NEPC by virtue of its ability to recapitulate the heterogeneity of prostate cancer. Moreover, we discuss the origin and the mechanism of NEPC. The understanding of the regulatory network mediating neuroendocrine differentiation presented in this review could provide valuable insights into the identification of novel drug targets for NEPC as well as into the causes of antiandrogenic drug resistance.

Mucinous tubular and spindle cell carcinoma: A difficult diagnosis

Mucinous Tubular and Spindle Cell Carcinoma (MTSCC) is infrequently seen renal malignancy with favorable outcome, when diagnosed in the early stage. Once out of kidney it is have lethal course. Radiologically MTSCC is heterogeneously hypo-enhancing renal mass in delayed phase, may mimic to papillary renal cell carcinoma and in histopathology showed these tumoral cells shows complex immunophenotype expression. As this does not show enhancement pattern of common renal cell carcinomas, radiological diagnosis may be challenging. Histopathological reporting is also tedious indeed necessary to reach definitive diagnosis, which help in tailoring follow up and prognosis. Metastatic disease has dismal outcome and responds poorly with adjuvant therapy and patient succumbs within short span of time.

Tubulocystic Renal Cell Carcinoma in Young Adult

Tubulocystic renal cell carcinoma is a uncommon neoplasm with unique pathological features and indolent clinical behaviour. We are reporting a case of tubulocystic renal cell carcinoma in young adult managed by partial nephrectomy.

Classification and Diagnosis of Cystic Renal Tumors: Role of MR Imaging Versus Contrast-Enhanced Ultrasound

Superior soft tissue and contrast resolution of MR imaging benefits sensitivity to kidney cyst features and classification, which may have an impact on patient management and outcomes. Contrast-enhanced ultrasound (CEUS) may have nearly similar sensitivity for detection of cyst features yet is dependent on patient body habitus and adequacy of visualization windows for the kidneys, which does not have the same impact on MR imaging results. Both MR imaging and CEUS may provide superior kidney cyst assessment compared with contrast-enhanced CT; however, further research is needed, particularly for the identification of role of CEUS.

Contemporary update on imaging of cystic renal masses with histopathological correlation and emphasis on patient management

This article presents an updated review of cystic renal mass imaging. Most cystic renal masses encountered incidentally are benign and can be diagnosed confidently on imaging and require no follow-up. Hyperattenuating masses discovered at unenhanced or single-phase enhanced computed tomography (CT) measuring between 20-70 HU are indeterminate and can be further investigated first by using ultrasound and, then with multi-phase CT or magnetic resonance imaging (MRI); as the majority represent haemorrhagic/proteinaceous cysts (HPCs). Dual-energy CT may improve differentiation between HPCs and masses by suppressing unwanted pseudo-enhancement observed with conventional CT. HPCs can be diagnosed confidently when measuring >70 HU at unenhanced CT or showing markedly increased signal on T1-weighted imaging. Although the Bosniak criteria remains the reference standard for diagnosis and classification of cystic renal masses, histopathological classification and current management has evolved: multilocular cystic renal cell carcinoma (RCC) has been reclassified as a cystic renal neoplasm of low malignant potential, few Bosniak 2F cystic masses progress radiologically during follow-up; RCC with predominantly cystic components are less aggressive than solid RCC; and Bosniak III cystic masses behave non-aggressively. These advances have led to an increase in non-radical management or surveillance of cystic renal masses including Bosniak 3 lesions. Tubulocystic RCC is a newly described entity with distinct imaging characteristics, resembling a pancreatic serous microcystadenoma. Other benign cystic masses including: mixed epithelial stromal tumours (MEST) are now considered in the spectrum of cystic nephroma and angiomyolipoma (AML) with epithelial cysts (AMLEC) resemble a fat-poor AML with cystic components.

Tubulocystic renal cell carcinoma: a review of literature focused on radiological findings for differential diagnosis

Tubulocystic renal cell carcinoma (TC-RCC) has been classified as an independent subtype according to the 2016 World Health Organization (WHO) classification. It is a rare subtype that predominantly affects men. Although few in number, radiological imaging reports have suggested that TC-RCC is characterized by multilocular cystic lesions, which are categorized as the Bosniak classification II-IV, with signature pathological characteristics comprising numerous small cysts or a tubular structure. The Bosniak classification system facilitates patient management; however, the differentiation of cystic tumors exhibiting similar imaging findings remains impossible; in fact, the differentiation of multilocular cystic RCC, adult cystic nephroma, and mixed epithelial and stromal tumor remains challenging. This review aims to discuss TC-RCC with a focus on implications of radiological findings in the differential diagnosis of TC-RCC.

Molecular Genetic Alterations in Renal Cell Carcinomas With Tubulocystic Pattern: Tubulocystic Renal Cell Carcinoma, Tubulocystic Renal Cell Carcinoma With Heterogenous Component and Familial Leiomyomatosis-associated Renal Cell Carcinoma. Clinicopathologic and Molecular Genetic Analysis of 15 Cases

The characteristic morphologic spectrum of tubulocystic renal cell carcinoma (TC-RCC) may include areas resembling papillary RCC (PRCC). Our study includes 15 RCCs with tubulocystic pattern: 6 TC-RCCs, 1 RCC-high grade with tubulocystic architecture, 5 TC-RCCs with foci of PRCC, 2 with high-grade RCC (HGRCC) not otherwise specified, and 1 with a clear cell papillary RCC/renal angiomyoadenomatous tumor-like component. We analyzed aberrations of chromosomes 7, 17, and Y; mutations of VHL and FH genes; and loss of heterozygosity at chromosome 3p. Genetic analysis was performed separately in areas of classic TC-RCC and in those with other histologic patterns. The TC-RCC component demonstrated disomy of chromosome 7 in 9/15 cases, polysomy of chromosome 17 in 7/15 cases, and loss of Y in 1 case. In the PRCC component, 2/3 analyzable cases showed disomy of chromosome 7 and polysomy of chromosome 17 with normal Y. One case with focal HGRCC exhibited only disomy 7, whereas the case with clear cell papillary RCC/renal angiomyoadenomatous tumor-like pattern showed polysomies of 7 and 17, mutation of VHL, and loss of heterozygosity 3p. FH gene mutation was identified in a single case with an aggressive clinical course and predominant TC-RCC pattern. The following conclusions were drawn: (1) TC-RCC demonstrates variable status of chromosomes 7, 17, and Y even in cases with typical/uniform morphology. (2) The biological nature of PRCC/HGRCC-like areas within TC-RCC remains unclear. Our data suggest that heterogenous TC-RCCs may be associated with an adverse clinical outcome. (3) Hereditary leiomyomatosis-associated RCC can be morphologically indistinguishable from "high-grade" TC-RCC; therefore, in TC-RCC with high-grade features FH gene status should be tested.

Morphological, immunohistochemical, and chromosomal analysis of multicystic chromophobe renal cell carcinoma, an architecturally unusual challenging variant

Chromophobe renal cell carcinoma (ChRCC) is typically composed of large leaf-like cells and smaller eosinophilic cells arranged in a solid-alveolar pattern. Eosinophilic, adenomatoid/pigmented, or neuroendocrine variants have also been described. We collected 10 cases of ChRCC with a distinct multicystic pattern out of 733 ChRCCs from our registry, and subsequently analyzed these by morphology, immunohistochemistry, and array comparative genomic hybridization. Of the 10 patients, 6 were males with an age range of 50-89 years (mean 68, median 69). Tumor size ranged between 1.2 and 20 cm (mean 5.32, median 3). Clinical follow-up was available for seven patients, ranging 1-19 years (mean 7.2, median 2.5). No aggressive behavior was documented. We observed two growth patterns, which were similar in all tumors: (1) variable-sized cysts, resembling multilocular cystic neoplasm of low malignant potential and (2) compressed cystic and tubular pattern with slit-like spaces. Raisinoid nuclei were consistently present while necrosis was absent in all cases. Half of the cases showed eosinophilic/oncocytic cytology, deposits of pigment (lipochrome) and microcalcifications. The other half was composed of pale or mixed cell populations. Immunostains for epithelial membrane antigen (EMA), CK7, OSCAR, CD117, parvalbumin, MIA, and Pax 8 were positive in all tumors while negative for vimentin, TFE3, CANH 9, HMB45, cathepsin K, and AMACR. Ki67 immunostain was positive in up to 1 % of neoplastic cells. Molecular genetic examination revealed multiple chromosomal losses in two fifths analyzable tumors, while three cases showed no chromosomal numerical aberrations. ChRCC are rarely arranged in a prominent multicystic pattern, which is probably an extreme form of the microcystic adenomatoid pigmented variant of ChRCC. The spectrum of tumors entering the differential diagnosis of ChRCC is quite different from that of conventional ChRCC. The immunophenotype of ChRCC is identical with that of conventional ChRCC. Chromosomal numerical aberration pattern was variable; no chromosomal numerical aberrations were found in three cases. All the cases in this series have shown an indolent and non-aggressive behavior.

A case of tubulocystic carcinoma of the kidney with aggressive features

Tubulocystic carcinoma of the kidney is rare and typically indolent. Our case involved an aggressive tubulocystic carcinoma as well as the radiological confirmation of its relation to papillary renal cell carcinoma. A 46-year-old male presented with renal multiloculated cysts with a solid part. On computed tomography and magnetic resonance imaging, the solid part showed the characteristics of papillary renal cell carcinoma. Contrast enhancement of the solid part was fluffy and sparse because of the coexistence of cysts. Perirenal fat invasion resulted in exophytic cysts, and renal-hilar cystic lymph node metastasis existed. The histopathological diagnosis was tubulocystic carcinoma associated with areas of papillary renal cell carcinoma and poorly differentiated carcinoma with metastasis. Our case suggests that the solid part enhancement of tubulocystic carcinoma tends to be fluffy and sparse, and exophytic cysts and cystic lymph nodes may show radiologically aggressive findings.

Mucinous tubular and spindle cell renal cell carcinoma: a review of clinicopathologic aspects

Mucinous tubular and spindle cell renal cell carcinoma is a rare, recently described variant of renal cell carcinoma characterized by an admixture of cuboidal cells in tubules and sheets of spindle cells, and variable amounts of mucinous stroma. It has been recognized as a distinct entity in the 2004 World Health Organization tumor classification. Since then, several dozen of these tumor have been reported with additional complementary morphologic characteristics, immunohistochemical profile, and molecular genetic features that have further clarified its clinicopathologic aspects. Although originally considered as a low grade renal cell carcinoma on the basis of its bland appearing nuclear features and indolent clinical course, mucinous tubular and spindle cell renal cell carcinoma has currently been proven to be a tumor that has a histological spectrum ranging from low to high grade that includes sarcomatoid differentiation. In this review, we present a detailed summary of the current knowledge regarding the clinicopathologic, immunohistochemical, molecular genetic, and prognostic characteristics, as well as differential diagnoses of mucinous tubular and spindle cell renal cell carcinoma.

Tubulocystic renal cell carcinoma: a new radiological entity

Tubulocystic renal cell carcinoma (TC-RCC) is a recently identified renal malignancy. While approximately 100 cases of TC-RCC have been reported in the pathology literature, imaging features have not yet been clearly described. The purpose of this review is to describe the main radiologic features of this rare sub-type of RCC on ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), based jointly on the literature and findings from a multi-institutional retrospective HIPAA-compliant review of pathology and imaging databases. Using a combination of sonographic and CT/MRI features, diagnosis of TC-RCC appeared to be strongly suggested in many cases.

KEY POINTS

• Tubulocystic renal cell carcinoma is a new entity with typical imaging features • Diagnosis of tubulocystic renal cell carcinoma can be suggested preoperatively by imaging • Cystic renal lesions with high echogenicity may correspond to tubulocystic carcinoma.

Mucinous tubular and spindle cell carcinoma (MTSCC) of the kidney: a detailed study of radiological, pathological and clinical outcomes

OBJECTIVE

To characterise the clinical, radiological and histological features of mucinous tubular and spindle cell carcinoma (MTSCC), as well as oncological outcomes.

PATIENTS AND METHODS

This is a single institution retrospective analysis of all patients with MTSCC from 2002 to 2011. Patients were excluded if MTSCC could not be confirmed on pathology re-review (four patients). Clinical characteristics, pathology, imaging, and outcomes were reviewed for the 19 included patients.

RESULTS

The median (range) age at diagnosis was 59 (17-71) years with a female predominance (78.9%). On contrast-enhanced computed tomography, MTSCC enhanced less than the cortex during the corticomedullary phase. The mean (range) tumour attenuation was 36 (24-48), 67 (41-133), 89 (49-152), and 76 (52-106) Hounsfield units in the pre-contrast, corticomedullary, nephrographic and excretory phases, respectively. In all, 16 patients were treated with partial (five patients) or radical nephrectomy (11) for pT1 (62.5%), pT2 (31.3%), and pT3a disease (6.3%). One patient underwent active surveillance. Of three patients (13.0%) managed with energy ablation, there was one recurrence that was treated with salvage surgery. One patient (5.3%) had metastatic disease at diagnosis and died from disease 64.7 months later. A patient with a pT2bN0M0 MTSCC with sarcomatoid dedifferentiation developed bone metastases 9.5 months after diagnosis and was alive at 19.0 months. The remainder were free of recurrence or progression.

CONCLUSION

MTSCC is a rare renal cell carcinoma (RCC) variant. In this largest series to date, MTSCC presented at a broad range of ages and displayed a female predilection. Imaging and pathological features of MTSCC display some overlap with papillary RCC. MTSCC is associated with excellent outcomes overall, but is not universally indolent.

Two Unexpected Tumors in a Laparoscopic Nephrectomy Specimen, Including a Rare Tubulocystic Renal-Cell Carcinoma: A Case Report

We present a case of a 52-year-old Caucasian male who underwent a laparoscopic nephrectomy for an atrophic kidney and was found to have two unexpected, synchronous kidney cancers. He had a remote history of testicular cancer complicated by lymphadenopathy and external ureteral compression. Over time, he developed an atrophic left kidney from obstructive uropathy. Years later, due to flank pain and renal scintigraphy showing minimal function, a laparoscopic nephrectomy was performed. Final pathology demonstrated papillary renal-cell carcinoma (RCC) and tubulocystic RCC. Tubulocystic RCC is a rare neoplasm thought to be an indolent subset of collecting duct carcinoma, but was identified as a unique entity in 2004. Currently, there are ∼100 cases of this neoplasm in the literature.

A New Type of Renal Cancer--Tubulocystic Carcinoma of the Kidney: A Review of the Literature

In 2004, A new peculiar subtype of renal cell carcinoma, which later received the name of tubulocystic carcinoma (TCC-RC), was recognized. Though the tumor has distinct macroscopic, microscopic and immunohistochemical features, the tumor was previously considered to have some similarities to various other renal cancers. We did an extensive review of literature using PubMed and CrossRef, which yielded more than 80 cases reported from various parts of the world. We evaluated the epidemiology, tumor presentations, pathological characteristics, treatment, and outcome of TCC-RC.

Tubulocystic carcinoma of the kidney: a histologic, immunohistochemical, and ultrastructural study

Tubulocystic carcinoma of the kidney (TCCK) is a tumor entity, which is not yet included in the WHO classification of renal tumors. The histogenesis of this neoplasm is uncertain. This study was undertaken to determine (1) the incidence of TCCK and (2) immunohistochemical and ultrastructural characteristics of those tumors that qualify as TCCK by the current definitions. From January 1, 2003 to December 31, 2012, a total of 615 renal cell carcinomas (RCCs) were seen by the Department of Pathology, University of Maryland Medical Center. Four TCCKs were identified (4/615, <1 %). TCCK is a distinctive group of kidney tumors with a male predominance and noteworthy macroscopic spongy appearance. Microscopically, the tumors were composed of tubules and cysts lined by a single layer of eosinophilic, columnar, cuboidal, flat, or hobnail cells with large nuclei and prominent nucleoli separated by a thin fibrotic stroma. In all TCCKs, the majority of neoplastic cells showed immunohistochemical (CD10(+), RCC(+), vimentin(+), and AMACR(+)) and ultrastructural (abundant long brush border microvilli) characteristics of proximal renal tubules. In few cells, the microvilli were shorter and sparse with cytoplasmic interdigitation analogous to intercalated cells of the collecting ducts. Focal positivity for BerEP4 (a marker preferentially expressed in distal renal tubules) was also noted. The major differential diagnostic considerations are oncocytoma, multilocular cystic renal cell carcinoma, and cystic nephroma/mixed epithelial and stromal tumor of the kidney. TCCK seems to have a favorable prognosis. In the current series, none of the patients had local recurrence or metastatic disease.

Mucinous tubular and spindle cell carcinoma of the kidney: imaging features

This article describes the features on sonography, computed tomography (CT) and magnetic resonance imaging (MRI) of mucinous tubular and spindle cell carcinoma of the kidney. Six pathologically proven cases of mucinous tubular and spindle cell carcinoma of the kidney were identified (5 females, 1 male); all patients underwent preoperative imaging. The mean age of the patients was 58.5 years. Thirteen imaging studies were available for review: 2 sonograms, 1 unenhanced CT scan, 5 contrast-enhanced CT scans, 1 unenhanced magnetic resonance imaging (MRI) examination, and 4 contrast-enhanced MRI examinations. Two abdominal radiologists evaluated all images retrospectively on a PACS workstation using a standardized data collection sheet until consensus was reached. All mucinous tubular and spindle cell carcinomas presented as well-marginated, small (mean 2.6 cm, range 1.9-3.2 cm) predominantly solid masses. No intratumoral fat or calcification was identified. Unenhanced CT and MRI appearances were variable as was the degree of enhancement following intravenous contrast material administration. There was no evidence of perinephric extension, renal vein involvement or metastatic disease in any of the cases. The radiological appearance of mucinous tubular and spindle cell carcinoma is diverse and therefore indistinguishable from the more common subtypes of renal cell carcinoma.

Tubulocystic renal carcinoma: a clinical perspective

INTRODUCTION

Tubulocystic renal carcinoma (TCRC) is a recently described neoplastic entity. To date, clinicopathological features on less than hundred cases of these rare tumours have been characterized exclusively in the pathological literature. Herein, we present five additional cases emphasizing clinical aspects on these rare renal neoplasms.

MATERIAL AND METHOD

Cases diagnosed as TCRC were retrieved and reviewed from the routine and consultation files of the Pilsen tumour registry comprising over 20,000 cases of renal tumours.

RESULTS

All patients were men, mean age 56 years (range 29-70). Features on computed tomography (CT) were in two cases Bosniak III, one IV and two were solid tumours. In four patients, nephrectomy was performed, and one patient underwent resection. At the time of surgery, two patients had metastases. In one case, both primary tumour and metastases were active on FDG positron emission tomography (PET)/CT. Both patients with metastatic disease were treated with sunitinib with partial response. One patient died 26 months postoperatively and the other patient is alive 5 months after surgery. Three patients with localized tumours are without evidence of disease 31, 28 and 7 months after surgery. In one case, the resected tumour was histologically combined with a papillary renal cell carcinoma (PRCC).

CONCLUSION

TCRC occurs predominantly in men with a wide age range. TCRC frequently displays a cystic component which may render a radiological classification of Bosniak III or IV. FDG PET/CT is helpful in the detection of metastases. TCRC has definitive malignant potential. Our findings support a possible relationship to PRCC. The tyrosine kinase inhibitor sunitinib may be used a therapeutical agent with partial response and temporary effect.

Comparison of gene expression profiles in tubulocystic carcinoma and collecting duct carcinoma of the kidney

The relationship between tubulocystic carcinoma and collecting duct carcinoma of the kidney remains controversial. Some experts are of the opinion that the tumors are related, considering tubulocystic carcinoma to be synonymous with low-grade collecting duct carcinoma. However, others maintain that the 2 are distinct, unrelated entities on the basis of morphologic features and clinical outcome. To explore the relationship between tubulocystic carcinoma and collecting duct carcinoma, we compared the expression of several gene products at the mRNA level in cohorts of each tumor subtype. Seven cases of tubulocystic carcinoma and 8 cases of collecting duct carcinoma were identified. Total RNA was isolated from formalin-fixed paraffin-embedded tissue from each case. Relative expression levels of vimentin, alpha methylacyl CoA racemase, E-cadherin, p53, CD10 antigen, parvalbumin, cytokeratin 7, and cytokeratin 19 were assessed by quantitative reverse transcription polymerase chain reaction. Tubulocystic carcinoma was characterized by relative overexpression of vimentin, p53, and alpha methylacyl CoA racemase, compared with collecting duct carcinoma (P<0.05 for each gene, t test). In general, tubulocystic carcinoma expressed higher levels of E-cadherin and CD10, whereas collecting duct carcinoma expressed higher levels of cytokeratin 19; however, these trends did not reach statistical significance in this study cohort. Tubulocystic carcinoma and collecting duct carcinoma did not express cytokeratin 7 differentially. Case-to-case variability of gene expression limited the effectiveness of any one marker to distinguish the tumor types. Our study demonstrates that tubulocystic carcinoma and collecting duct carcinoma have different expression profiles of selected genes, including vimentin, p53, and alpha methylacyl CoA racemase. Further analysis of additional cases, using quantitative reverse transcription polymerase chain reaction and immunohistochemistry, will be useful to test the reproducibility of these findings. In addition, larger studies may establish statistical differences in expression of other genes analyzed in this study. Overall, these findings support the view that tubulocystic carcinoma and collecting duct carcinoma should be considered as 2 distinct entities at the molecular level.

Renal tubulocystic carcinoma is closely related to papillary renal cell carcinoma: implications for pathologic classification

Tubulocystic carcinoma of the kidney (TC-RCC) is a rare renal tumor with unique gross and microscopic features unlike other types of renal cell carcinoma (RCC). Several recent studies recommend that it should be classified as a distinct RCC subtype. In this study, we provide pathologic and cytogenetic evidence supporting that TC-RCC is closely related to papillary RCC (PRCC). This study included 20 cases of renal tumors that partially or exclusively comprised a TC-RCC component. Pathologic examination documented the gross and microscopic features of TC-RCC, including multicentricity and the presence of concomitant PRCC and papillary adenoma. Formalin-fixed, paraffin-embedded sections from 12 TC-RCC and 20 PRCC were subjected to a multicolor fluorescence in situ hybridization assay containing probes for chromosomes 7, 17, and Y. One hundred nuclei were examined to enumerate the copy numbers of chromosomes in each tumor and its corresponding normal kidney tissue. A tumor with a percentage of cells harboring a chromosomal change > or = mean+3 SD of normal tissue was considered to harbor that chromosomal change, and a tumor with a percentage of cells with null Y chromosome count (loss of Y chromosome) > or = mean+3 SD of normal tissue was considered to harbor Y chromosome loss. Four of the 20 TC-RCCs were multicentric. Ten had associated PRCC or papillary adenoma within the same kidney as the TC-RCC. In 4 cases, the tubulocystic and papillary components were admixed together within the same lesion. The tumor cells lining both the tubulocystic and papillary components had similar cytologic features. Ten of 12 TC-RCCs had a chromosome 7 gain, 8 of 12 cases had a chromosome 17 gain, and 8 of 9 cases had a loss of Y chromosome. Six of 9 cases with all 3 chromosomes studied had a gain of chromosomes 7 and 17 and a loss of Y chromosome. Our study shows that TC-RCCs and PRCCs are closely related entities. With its distinctive gross and microscopic features, TC-RCC may be considered a unique "morphologic entity." However, before it is accepted as a distinct renal cell carcinoma subtype, further studies are needed to document a characteristic molecular signature associated with this tumor.

A case of renal mucinous tubular and spindle cell carcinoma

A 33-year-old man was hospitalized for treatment of a left renal tumor. The radiological findings were consistent with those of a left renal cell carcinoma (RCC). Subsequently, a radical nephrectomy was carried out. Macroscopic examination showed that a well-demarcated tumor measuring 2.9 x 2.6 x 2.5 cm was present in the middle portion of the resected kidney. The cut surface of the tumor was grayish-white in color. Pathological examination of the resected specimen showed a mucinous tubular and spindle cell carcinoma of the kidney (MTSCC-K). MTSCC-K is a low-grade renal epithelial neoplasm that has recently been recognized as a specific entity in the World Health Organization 2004 classification of RCC. To our knowledge, 17 cases of MTSCC-K in Japan have been reported by Japanese investigators. To avoid administration of excessive adjuvant treatment to patients, pathologists and urologists should consider this newly recognized low-grade malignancy when diagnosing renal tumors.

Uncommon and recently described renal carcinomas

Major consensus conferences held over a decade ago laid the foundations for the current (2004) WHO classification of renal carcinoma. Clear cell, papillary and chromophobe carcinomas account for 85-90% carcinomas seen in routine practice. The remaining 10-15% of carcinomas consist of rare sporadic and hereditary tumors, some of which had been long recognized, but many of which only emerged as distinct entities in the decade leading up to the WHO publication. Collecting-duct carcinoma is a rare, often lethal form of carcinoma. Medullary carcinoma associated with sickle cell trait, has emerged as a distinctive tumor showing some overlapping features with upper tract urothelial carcinoma. Mucinous tubular and spindle-cell carcinoma and tubulocystic carcinoma were earlier considered as patterns of low-grade collecting-duct carcinoma, but are now recognized as separate tumor entities. Carcinomas associated with somatic translocations of TFE3 and TFEB comprise a significant proportion of pediatric renal carcinomas. Oncocytoid renal carcinomas in neuroblastoma survivors was recognized as a unique tumor category in the WHO classification. Renal carcinoma associated with end-stage renal disease is now recognized as having distinct morphological patterns and behavior. In addition there is a group of rare recently described carcinomas, including clear cell papillary carcinoma, oncocytic papillary renal cell carcinoma, follicular renal carcinoma and leiomyomatous renal cell carcinoma. It behooves the surgical pathologist to not only be capable of diagnosing the common forms of renal cancer, but also to be aware of the rare types of renal carcinoma, many of which have emerged in recent years.

Tubulocystic carcinoma of the kidney: clinicopathologic analysis of 31 cases of a distinctive rare subtype of renal cell carcinoma

A distinctive tumor described under the terms Bellini duct carcinoma and low-grade collecting duct carcinoma has been referred to by us and others as tubulocystic carcinoma. This renal cell carcinoma subtype is not recognized in the World Health Organization 2004 classification. Herein, we present a detailed study of 31 cases to further characterize this rare subtype of renal cell carcinoma. The tumor occurred in adults (mean age, 54 years) with a strong male predominance (7:1). Grossly, the tumors ranged from 0.7 to 17 cm, and exhibited a spongy or "bubble wrap" appearance reflecting the microscopic presence of variably sized cystically dilated tubules lined by a single layer of epithelium. The lining varied with a cuboidal, flat, and hobnail cell appearance, and the neoplastic cells had abundant eosinophilic cytoplasm and enlarged nuclei with prominent nucleoli. The cysts were closely spaced with an intervening variably fibrotic stroma. Immunohistochemistry and ultrastructural examination showed features of proximal convoluted tubules (Pax 2 immunoreactivity and short microvilli with brush border organization) and distal nephron (kidney-specific cadherin immunoreactivity and cytoplasmic interdigitation). Gene expression profiling showed that tubulocystic carcinoma displayed a unique molecular signature. Twenty-four tumors were stage pT1, 4 stage pT2, and 3 stage pT3. Disease progression (median follow-up of 56 months) occurred in 3 patients; 1 with local recurrence, and 2 with distant metastasis to bone and liver. In light of the distinctive clinicopathologic features and a low but definite metastatic potential, this unique subtype of renal cell carcinoma deserves formal recognition in the contemporary classification of renal neoplasms.

Primary thyroid-like follicular carcinoma of the kidney: report of 6 cases of a histologically distinctive adult renal epithelial neoplasm

Thyroidization of kidney reminiscent of thyroid follicles with accumulation of inspissated colloid-like material in renal tubules is a hallmark of chronic pyelonephritis. We identified 6 tumors in the kidney, distinct from currently known subtypes of renal cell carcinoma, with a striking histology that closely mimicked well-differentiated thyroid follicular neoplasms and raised the possibility of metastatic follicular thyroid carcinoma. Three occurred in males and 3 in females with an age range of 29 to 83 years and size range from 1.9 to 4 cm. All tumors were encapsulated and exclusively demonstrated follicular architecture comprising of microfollicles and macrofollicles containing inspissated colloid-like material. A minor component of small tightly packed follicles devoid of secretions was also noted. The follicles were lined by cells with moderate amphophilic to eosinophilic cytoplasm with round nuclei and occasional prominent nucleoli. The tumors were nonimmunoreactive with thyroglobulin and thyroid transcription factor 1 and for markers contemporarily used for renal differentiation. The tumors had a gene expression profile distinct from clear cell and chromophobe renal cell carcinoma. Comparative genetic hybridization failed to reveal cytogenetic alterations. Mean follow-up of 47.3 months (range: 7 to 84 mo) showed that 5 patients had no evidence of disease and 1 developed a metastasis to the renal hilar lymph nodes in which the follicular architecture with colloid was retained. Thyroid-like follicular renal cell carcinoma represents a unique histologic subtype of renal cell carcinoma of low malignant potential and its primary importance is to distinguish it from metastatic carcinoma from the thyroid.

Tubulocystic carcinoma of the kidney: clinicopathologic and molecular characterization

The nature of tubulocystic carcinoma, a rare renal tumor composed of tubular and cystic structures, is poorly understood. It has been suggested that it may represent a low-grade collecting duct carcinoma of the kidney despite the lack of sufficient molecular and pathologic evidence. The aim of this study was to examine the clinical and pathologic features of 13 cases of tubulocystic carcinoma of the kidney. Furthermore, using gene expression microarray analysis, we defined the molecular signature of this tumor by comparing it with other renal tumors in our previously established molecular profile database. Histologically, all 13 tumors were composed of closely packed tubules and cysts of varying sizes separated by fibrovascular septa. The epithelial lining cells of the tubules and cysts in this tumor were characterized by abundant eosinophilic cytoplasm with prominent nucleoli often showing a hobnail appearance. Clinically, one of the 13 cases showed metastasis to the pelvic lymph nodes. Five of the 13 cases coexisted with papillary renal cell carcinoma (RCC) (n=3) or papillary adenoma (n=2). In addition, the molecular profile of tubulocystic carcinoma was similar but not identical to those of papillary RCC by clustering analysis. Through comparative genomic microarray analysis, tubulocystic carcinoma showed gains of chromosome 17, but not chromosome 7, whereas most papillary RCCs showed chromosomal gains in both 7 and 17 (trisomies). Therefore, based on its unique pathologic features and molecular signature as well as its biologic behavior to develop metastasis either by itself or in association with papillary RCC, tubulocystic carcinoma of the kidney should be recognized as a distinct subtype of RCC and be distinguished from other malignant and benign cystic lesions of the kidney.

Cystic nephroma and mixed epithelial and stromal tumour of the kidney: opposite ends of the spectrum of the same entity?

OBJECTIVES

The term "renal epithelial and stromal tumour" (REST) was proposed recently to encompass the spectrum of findings observed in cystic nephroma (CN) and mixed epithelial and stromal tumour (MEST) of the kidney. Our aim was to review the broad spectrum of usual and unusual clinical and morphologic findings observed in CN and MEST.

METHODS

Based on Medline database searches, all aspects of CN and MEST were assessed.

RESULTS

CN and MEST have a remarkable similarity in sex predilection, age distribution, and morphologic attributes of both the epithelial and stromal components and immunohistochemical profile, albeit with variation in individual categories, with higher prevalence of stromal-to-epithelial ratio, prominent ovarian-like stroma, smaller cysts, and stromal luteinisation in MEST, and large cysts, thin septa, and low stromal-to-epithelial ratio in CN. The stromal component in both lesions expresses estrogen and progesterone receptors. Rare and unusual morphologic features, such as endometrioid, cervical, and intestinal differentiation, and luteinised ovarian-like stroma, have been described in MEST. The epithelial element occasionally shows estrogen and progesterone receptors. Rare aggressive behaviour has been reported for both neoplasms.

CONCLUSIONS

Considerable overlap is apparent between the two lesions, which suggests that they may represent opposite ends of the spectrum of the same process. Even though an aggressive behaviour has been reported in very few cases, in general both neoplasms are considered benign and surgical excision is curative.

Tubulocystic carcinoma of the kidney: a new entity among renal tumors

Tubulocystic carcinoma is a tumor entity, which is not yet included in the WHO-classification of renal tumors. We report a series of 11 cases of this tumor, 6 of which were examined in by immunohistochemistry using a panel of five antibodies (CK7, CK34betaE12, CK19, CD10 and P504S). All patients were men. Each had renal tumor stage of pT1N0M0, with a diameter of 1.7 to 7 cm (mean, 3.3 cm). None of the patients presented with recurrence or metastases. Grossly, tumors were microcystic masses with a bubble-wrap appearance. Histological features included cysts and small tubules, separated by delicate septa and lined by flat to columnar or hobnail cells. The cyst and tubule epithelium showed immunohistochemical characteristics of both proximal and distal tubules. Tubulocystic carcinoma is a distinctive kidney tumor, with noteworthy macroscopic and microscopic characteristics, which can be distinguished from other cystic kidney tumors, including cystic nephroma, multilocular cystic renal cell carcinoma and some solid tumors with extensive cystic changes. More cases are needed to ascertain its prognosis. Tubulocystic carcinoma should be considered as a new subtype of renal cell carcinoma in the next revision of the WHO classification.

Expanding the histologic spectrum of mucinous tubular and spindle cell carcinoma of the kidney

Mucinous tubular and spindle cell carcinomas (MTSCs) are polymorphic neoplasms characterized by small, elongated tubules lined by cuboidal cells and/or cords of spindled cells separated by pale mucinous stroma. Nonclassic morphologic variants and features of MTSC have not been well studied. We identified 17 previously unreported MTSCs from Surgical Pathology and consultative files of the authors and their respective institutions and studied their morphologic features. A total of 10/17 cases were considered "classic," as described above, with 5/10 showing at least focal (20% to 50%) tubular predominance without apparent mucinous matrix. Alcian blue staining revealed abundant (>50%) mucin in all classic cases. Seven of 17 MTSCs were classified as "mucin-poor," with little to no extracellular mucin appreciable by hematoxylin and eosin. Four of these cases showed equal tubular and spindled morphology, 2 cases showed spindle cell predominance (70%; 95%), and 1 case showed tubular predominance (90%). In 5/7 mucin-poor cases, staining for Alcian blue revealed scant (<10%) mucin in cellular areas with the other 2 cases having 30% mucin. Unusual histologic features identified in the 17 cases were: foamy macrophages (n=8), papillations/well formed papillae (n=6/n=1), focal clear cells in tubules (n=3), necrosis (n=3), oncocytic tubules (n=2; 40%, 5%), numerous small vacuoles (n=2), heterotopic bone (n=1), psammomatous calcification (n=1), and nodular growth with lymphocytic cuffing (n=1). An exceptional case contained a well-circumscribed, HMB45-positive angiomyolipoma within the MTSC. MTSCs may be "mucin-poor" and show a marked predominance of either of its principal morphologic components, which coupled with the presence of other unusual features such as clear cells, papillations, foamy macrophages, and necrosis, may mimic other forms of renal cell carcinoma. Pathologists must be aware of the spectrum of histologic findings within MTSCs to ensure their accurate diagnosis.

[WHO classification 2004: tumors of the kidneys]

New entities, confirmed either by cytogenetic findings or by new molecular markers, have been included in the WHO 2004 renal tumor classification. Moreover, imaging improvements provide a better radiologic description of tumors. In this article, we will discuss the WHO 2004 classification and focus on the new entities and their macroscopic appearance. We will especially insist on the following entities: multilocular clear cell renal carcinoma, Xp11 translocation carcinoma, low-grade mucinous tubular carcinoma, epithelioid angiomyolipoma, and benign mixed epithelial and stromal tumor. We also discuss the new concept of hybrid oncocytoma and chromophobe renal cell carcinoma, as well as the Birt-Hogg-Dube syndrome, which is associated with kidney tumors.

[Immunohistochemical profile and clinical features of mucinous tubular and spindle renal cell carcinoma]

INTRODUCTION

We present the immunohistochemical (IHC) analyses of a series of four kidney tumors currently classified as mucinous tubular and spindle renal cell carcinoma (WHO), a tumor with uncertain histogenesis and differentiation. Our aims were to determine an immunoprofile and to add clinical and morphological information about this rare renal carcinoma.

MATERIAL AND METHODS

The four tumors were found between 415 renal carcinomas at our center (0.89%). IHC was carried out with a panel of antibodies in these four cases. Morphogical and clinical information was collected and analyzed.

RESULTS

All tumors were well circumscribed and confined to the kidney. Immunoreactivity for cytokeratin (CK)7 was intense and diffuse. Immunostaining was variable for EMA, vimentin, S-100, Ulex europaeus antigen, high-molecular-weight CK, CK 8, CK18, and CK 19. The tumors were homogeneously negative for CEA, CD15, CD10, CD34, desmin, actin, CK10, CK20, and HMB45. Proliferative index (Ki67) was <1% en all cases. The immunoreactivity was similar in cuboidal and spindle cells.

CONCLUSIONS

The present tumor shows a variable immunophenotype and there is not a precise cell type differentiation. The immunostaining in cuboidal and spindle cells suggests a similar differentiation and histogenesis.

Renal mucinous tubular and spindle carcinoma lacks the gains of chromosomes 7 and 17 and losses of chromosome Y that are prevalent in papillary renal cell carcinoma

Mucinous tubular and spindle cell carcinoma of the kidney is an uncommon, distinctive neoplasm characterized by the proliferation of cuboidal and spindle cells arranged in tubular or sheet-like arrays, typically with a mucinous or myxoid background. The most important differential diagnostic consideration of mucinous tubular and spindle cell carcinoma is papillary renal cell carcinoma, type 1, with sarcomatoid transformation. The aim of our study is to investigate the pattern of possible gains or losses of chromosomes 7, 17 and Y in 10 mucinous tubular and spindle cell carcinomas with interphase fluorescence in situ hybridization (FISH). Four-micron sections were obtained from paraffin blocks representative of the tumors and including adjacent non-neoplastic renal parenchyma from 10 patients. The patients' ages ranged from 20 to 80 years (mean: 62 years); eight were female, while two were male. FISH analysis was performed with centromeric probes for chromosomes 7, 17 and Y. One hundred fifty to 200 nuclei from each case were scored for hybridization signals and non-neoplastic parenchyma served as control tissue. We found that renal mucinous tubular and spindle carcinoma lacks the gains of chromosomes 7 and 17 and losses of chromosome Y that are typical of papillary renal cell carcinoma. FISH analysis with centromeric probes for these chromosomes is potentially helpful in differentiating mucinous tubular and spindle cell carcinomas from papillary renal cell carcinomas.

Renal cystic diseases: a review

This review aims to assist in the categorization of inherited, developmental, and acquired cystic disease of the kidney as well as to provide a pertinent, up-to-date bibliography. The conditions included are autosomal-dominant polycystic kidney disease, autosomal-recessive polycystic kidney disease, unilateral renal cystic disease (localized cystic disease), renal simple cysts, multicystic dysplastic kidney, pluricystic kidney of the multiple malformation syndromes, juvenile nephronophthisis and medullary cystic disease, medullary sponge kidney, primary glomerulocystic kidney disease, and glomerulocystic kidney associated with several systemic disorders mainly of genetic or chromosomal etiology, cystic kidney in tuberous sclerosis, and in von Hippel-Lindau syndrome, cystic nephroma, cystic variant of congenital mesoblastic nephroma, mixed epithelial stromal tumor of the kidney, renal lymphangioma, pyelocalyceal cyst, peripylic cyst and perinephric pseudocyst, acquired renal cystic disease of long-term dialysis, and cystic renal cell carcinoma and sarcoma. Whereas the gross and histologic appearance of some of these conditions may be diagnostic, clinical and sometimes molecular studies may be necessary to define other types.