Renal oncocytoma with and without intravascular extension into the branches of renal vein have the same morphological, immunohistochemical, and genetic features

Renal oncocytoma with adverse pathologic features: a clinical and pathologic study of 50 cases

Renal oncocytoma is the most common benign epithelial renal neoplasm. Several adverse features that would typically increase the stage of renal cell carcinomas are not uncommon in renal oncocytoma, including perinephric, sinus fat, or renal vein invasion. Herein, we report the largest single institutional series of renal oncocytoma with adverse pathologic features. The cohort comprised 50 patients, 38 were men (76%) and 12 were women (24%), with a mean age of 68 years (range, 50-87 years). All cases were diagnosed on nephrectomy specimens. No laterality predilection was noted. The tumors ranged in size from 1.5-15.7 cm (mean, 5.3 cm). Adverse pathologic features included perinephric fat invasion (n = 25; 50%), renal sinus fat invasion (n = 9; 18%), and renal vein invasion (n = 5; 10%). More than one adverse feature was seen in 11 tumors (22%). All tumors showed diffuse reactions to KIT (n = 40; 100%) and cyclin D1 (n = 27; 100%). Keratin 7 highlighted rare (<5%) scattered cells, as well as entrapped renal tubules (n = 21; 100%). Reaction to DOG1 was patchy in three tumors (n = 27; 11%) while reactions to vimentin (n = 31) and Hale colloidal iron special stain (n = 30) were negative. On follow-up, no tumor recurrence or metastasis was observed over a follow-up range of 1-144 months (mean, 54 months; median, 60 months). Our data suggest that adverse pathologic features in renal oncocytoma do not alter their benign course.

Renal cell carcinoma staging: pitfalls, challenges, and updates

Renal cell carcinoma (RCC) is unusual among cancers in that it often grows as a spherical, well-circumscribed mass. Increasing tumour size influences the pathological pT stage category within pT1 and pT2, with cutoffs of 40, 70 and 100 mm; however, with increasing size also comes a sharp increase in the likelihood of renal sinus or renal vein tributary invasion, such that clear cell RCC rarely reaches 70 mm without invading one of these. To clarify some previous challenges in assigning tumour stage, the American Joint Committee on Cancer 2016 tumor-node-metastasis classification has removed the requirements than vein invasion be recognised grossly and that vein walls contain muscle for the diagnosis of vein invasion. Renal pelvis invasion has also been added as an additional route to pT3a. Multinodularity or finger-like extensions from a renal mass should be viewed with great suspicion for the possibility of vein or renal sinus invasion, and, as tumour size increases to over 40-50 mm, thorough sampling of the renal sinus interface should always be undertaken. With increasing interest in adjuvant therapy in renal cancer, the pathologist's role in RCC staging will continue to be an important prognostic parameter and a tool for selection of patients for enrolment in clinical trials.

Chromophobe Renal Cell Carcinoma With Retrograde Venous Invasion and Gain of Chromosome 21: Potential Harbingers of Aggressive Clinical Behavior

Occasionally, renal cell carcinoma (RCC) with renal vein extension spreads against the flow of blood within vein branches into the kidney, forming multifocal nodules throughout the renal parenchyma. These foci are not regarded as multiple tumors but rather reverse spread of tumor along the venous system. This intravascular spread has previously been reported in clear cell RCC and RCC unclassified. However, to our knowledge, this has never been reported in chromophobe RCC. Chromophobe RCC is a unique histologic subtype of renal cancer, generally thought to have less aggressive behavior. However, it nonetheless has the potential to undergo sarcomatoid dedifferentiation, which is associated with poor prognosis. We report a unique case of a 65-year-old man with chromophobe RCC (pT3a) showing classic morphology (nonsarcomatoid), yet presenting with retrograde venous invasion and hilar lymph node metastasis at the time of right radical nephrectomy. Fluorescence in situ hybridization revealed gain of chromosome 21 with loss of multiple other chromosomes. Partial hepatectomy was performed to resect metastatic RCC 7 months after nephrectomy, revealing chromophobe RCC with classic morphology. Bone biopsy confirmed skeletal metastases 38 months after initial diagnosis. Although invasion of the renal vein and retrograde venous invasion are characteristically seen in clear cell RCC, this unusual phenomenon may also occur in chromophobe RCC, despite its unique tumor biology. This and gain of chromosome 21, which was postulated to be associated with aggressive behavior in a previous report, were associated with adverse behavior in our patient, who had short-term progression to multi-organ metastatic disease.

Modern Pathologic Diagnosis of Renal Oncocytoma

Oncocytoma is a well-defined benign renal tumor, with classic gross and histologic features, including a tan or mahogany-colored mass with central scar, microscopic nested architecture, bland cytology, and round, regular nuclei with prominent central nucleoli. As a result of variations in this classic appearance, difficulty in standardizing diagnostic criteria, and entities that mimic oncocytoma, such as eosinophilic variant chromophobe renal cell carcinoma and succinate dehydrogenase-deficient renal cell carcinoma, pathologic diagnosis remains a challenge. This review addresses the current state of pathologic diagnosis of oncocytoma, with emphasis on modern diagnostic markers, areas of controversy, and emerging techniques for less invasive diagnosis, including renal mass biopsy and advanced imaging.

Imaging of Solid Renal Masses

Detection of solid renal masses has increased, although it has not resulted in significant mortality reduction from renal cell carcinoma. Efforts for improved lesion characterization have been pursued and incorporated in management algorithms, in order to distinguish clinically significant tumors from favorable or benign conditions. Concurrently, imaging methods have produced evidence supporting their role as useful tools not only in lesion detection but also characterization. In addition, newer modalities, such as contrast-enhanced ultrasonography, and advanced applications of MR imaging, are being investigated. This article reviews the current role of different imaging methods in the characterization of solid renal masses.

Renal oncocytoma with vascular invasion: a series of 22 cases

Renal oncocytomas are benign neoplasms that are often excised, as clinically they cannot be distinguished with certainty from renal cell carcinoma. One of the least common findings in oncocytomas is vascular invasion, and their behavior is not well characterized with only reports of isolated examples and smaller case series. Whether vascular invasion is acceptable for the diagnosis of oncocytoma still remains controversial, even amongst genitourinary pathologists with expertise in renal tumor pathology. Of 1474 cases of renal oncocytoma identified at 3 large medical centers, 22 (1.5%) had vascular invasion. Patients included 12 men and 10 women with an average age at diagnosis of 67.5 years (range, 48-91 years). Thirteen cases showed large vessel invasion, and the remainder involved medium or small vessels. Tumor was grossly visible in the renal vein in 2 cases. Clinical data were available on 16 of the 22 cases with an average follow-up time of 29.9 months (range, 7.5-94.5 months). Of the cases with clinical follow-up, all but one individual was alive. All living individuals were free of recurrence or metastatic disease at the time of last follow-up. Our cohort showed no metastasis or recurrence and overall survival of 94.7% at 2.5 years following diagnosis, supporting the finding that vascular invasion does not alter the favorable prognosis of oncocytoma. The presence of vascular invasion should not lead to any uncertainty about the diagnosis in an otherwise typical oncocytoma.

Updates in Benign Lesions of the Genitourinary Tract

The genitourinary tract is a common site for new cancer diagnosis, particularly for men. Therefore, cancer-containing specimens are very common in surgical pathology practice. However, many benign neoplasms and nonneoplastic, reactive, and inflammatory processes in the genitourinary tract may mimic or cause differential diagnostic challenges with malignancies. Emerging clinicopathologic, immunohistochemical, and molecular characteristics have shed light on the pathogenesis and differential diagnosis of these lesions. This review addresses differential diagnostic challenges related to benign genitourinary tract lesions in the kidney, urinary bladder, prostate, and testis, with emphasis on recent advances in knowledge and areas most common in diagnostic practice.

Pleomorphic adenoma of the salivary glands with intravascular tumor deposits: a diagnostic pitfall

The diagnosis of pleomorphic adenoma (PA) of salivary glands is usually straightforward posing few diagnostic problems for the general surgical histopathologist. The purpose of our investigation was to present a series of 22 cases of PA of major salivary glands, each of which contained small foci of tumor within vascular spaces. This feature has previously been described very rarely in PA and may represent a significant diagnostic pitfall. The patients included 12 women and 10 men, ranging in age at diagnosis from 17 to 82 years. Histopathologically, all 22 tumors displayed the features of PA with mixed epithelial and myoepithelial growth patterns and chondromyxoid areas. None of these neoplasms showed any cytologic evidence of malignancy. In all cases, there were multiple dilated thin-walled and/or muscular thick-walled blood vessels containing small intraluminal collections of neoplastic cells with or without myxoid stromal components. The intravascular tumor cells expressed cytokeratins, and in some cases they were also immunoreactive for S-100 protein, GFAP, D2-40, and p63 protein. The intravascular location of the neoplastic cells was confirmed by CD31, CD34, and factor VIII-related antigen immunostains. Reaction for D2-40 was negative in the endothelium of the involved vessel in all cases, confirming that they were vascular rather than lymphatic channels. Seven patients (36%) underwent fine-needle aspiration biopsy 25 days to several years before excision of the tumor. Follow-up of the patients in our series revealed no cases of recurrence or metastasis (range, 6 mo to 9.5 y; mean 3.8 y; median 3.5 y). The biological significance of intravascular tumor in PA is not clear, but there is growing evidence that it is an innocuous phenomenon that might be related to artifactual spillage caused by tumor injury presumably by either fine-needle aspiration or intraoperative trauma.

Tubulocystic renal cell carcinoma: is there a rational reason for targeted therapy using angiogenic inhibition? Analysis of seven cases

Generally, patients with renal cell carcinoma (RCC) are viewed as potential candidates for antiangiogenic targeted therapy. Tubulocystic RCC (TCRC) is a recently described entity which may behave aggressively, and the rationale for antiangiogenic therapy in this group of renal tumors has yet to be determined. Seven TCRCs and five non-tumor tissue samples from seven patients were subjected to relative expression analysis of mRNA levels of 16 genes involved in three angiogenic signal pathways: (1) VHL/HIF, (2) RTK/mitogen-activated protein kinase (MAPK), and (3) PI3K/Akt/mTOR. Two of them, pathways (2) and (3), are often targeted by antiangiogenic agents. We also determined the mutation and methylation status of the VHL gene. Finally, the levels of vascular endothelial growth factor A (VEGFA), HIF-1α, HIF-2α proteins, and phosphorylated mTOR protein were also determined. The comparison of tumor and control samples revealed no changes of mRNA levels of the following genes: VHL, HIF-1α, HIF-2α, PTEN, Akt2, Akt3, mTOR, VEGFA, KDR, HRas, C-Jun, EGFR, and FGF2. Significantly elevated mRNA level of TP53 was found, while the mRNA levels of FLT1 and C-FOS were reduced in tumor samples. No mutations or methylation in the VHL gene were found. Changes in levels of studied proteins VEGFA, HIF-1α, HIF-2α, and increased phosphorylation of mTOR protein were not found. Three studied angiogenic pathways (VHL/HIF, RTK/MAPK, and PI3K/Akt/mTOR) seem not to be upregulated in TCRC samples, so there appears to be no rationale for a general recommendation of antiangiogenic targeted therapeutic protocols for patients with these tumors.

LMP2, a novel immunohistochemical marker to distinguish renal oncocytoma from the eosinophilic variant of chromophobe renal cell carcinoma

LMP2 is a subunit of the immunoproteasome that is overexpressed in oncocytic lesions of the thyroid gland. This study was designed to assess the expression profile and diagnostic utility of LMP2 in two renal oncocytic tumors that share similar morphologic features but have different clinical outcomes: renal oncocytoma (RO) and the eosinophilic variant of chromophobe renal cell carcinoma (CHRCC-EO). A total of 56 RO, 38 classic CHRCC, and 7 CHRCC-EO cases, as well 84 normal kidney controls, were selected from the Johns Hopkins surgical pathology archive and stained for LMP2 using a standard immunohistochemical protocol. Sections were scored for cellular location (nuclear versus cytosolic), intensity (from 0 to 3), and percent of area involved (from 0 to 100%), and an H score was calculated multiplying the intensity by the extent of the staining signal. The cytoplasmic expression of LMP2 was similar among the renal lesions, being present in 44 of 56 (79%) ROs, 27 of 38 (71%) CHRCCs, and 7 of 7 (100%) CHRCC-EO cases. The nuclear expression of LMP2, however, was more informative. All CHRCC-EO cases (7 of 7, 100%) strongly showed nuclear LMP2 staining, as opposed to only 2 of 56 (4%, P<0.0001) ROs and 9 of 38 (24%, P=0.0001) classic CHRCCs. These results suggest that the nuclear LMP2 expression can be used in clinical scenarios where histological distinction between RO and CHRCC-EO remains challenging.

Selected common diagnostic problems in urologic pathology: perspectives from a large consult service in genitourinary pathology

CONTEXT

Several common differential diagnoses are encountered in urologic pathology, frequently causing patient referrals for a second opinion.

OBJECTIVES

To review 3 common differential diagnoses encountered in a large consultation service in genitourinary pathology, including partial atrophy versus prostatic acinar adenocarcinoma, oncocytoma versus chromophobe renal cell carcinoma, and urothelial carcinoma in situ versus normal urothelium and reactive atypia. We will discuss the detailed, morphologically distinctive features and the usefulness of immunohistochemistry.

DATA SOURCES

Personal experience and review of the current literature.

CONCLUSIONS

Careful morphologic assessment and awareness of diagnostic pitfalls are fundamental in reaching a definitive diagnosis in most cases. Immunohistochemistry is useful but should be used only in conjunction with the morphologic impression.

Cutaneous apocrine mixed tumor with intravascular tumor deposits: a diagnostic pitfall

Apocrine mixed tumor of the skin is a benign adnexal neoplasm usually posing no diagnostic problem for a histopathologist. The purpose of our investigation is to present a small series of 4 benign cutaneous apocrine mixed tumors of the skin that contained small foci of intravascular tumor deposits, a feature not previously described, to the best of our knowledge. The 4 lesions were identified retrospectively after a review of 312 apocrine mixed tumors and 51 eccrine mixed tumors in the collective files of the authors. In all cases, this feature was originally overlooked. The patients were 3 men and 1 woman, ranging in age at diagnosis from 29 to 66 years. Locations included nose (2), forehead (1), and the fifth toe (1). Histopathologically, all 4 neoplasms demonstrated typical features of a benign apocrine mixed tumor; 2 cases were classified as hyaline cell-rich tumors. In all cases, there were either blood or lymphatic vessels containing small intraluminal collections of neoplastic cells, which had the appearances of hyaline cells and immunohistochemically expressed cytokeratins and were partly immunoreactive for S-100 protein and calponin, thus indicating the myoepithelial phenotype. The intravascular location of the neoplastic cells was confirmed by CD31 staining. The nature of the vessels (lymphatics vs. blood vessels) was supported by staining for alpha smooth muscle actin, which stained pericytes in blood vessels. Lymphatic vessels were also stained for D2-40. No eccrine mixed tumor manifested intravascular tumor deposits. Follow-up of the patients revealed no recurrences or metastasis (range: 2-21 years). It is concluded that occurrence of intravascular involvement in benign apocrine mixed tumor of the skin is rare (approximately 1%-2%). This feature is discrete and is easy to overlook. At present, its significance is not completely clear. Until proved otherwise in future, we suggest to consider intravascular deposits in cutaneous apocrine mixed tumors as an innocuous phenomenon.

Imprint cytologic features of chromophobe renal cell carcinoma morphologically resembling renal oncocytoma: is this an oncocytic variant of chromophobe renal cell carcinoma?

In this article, we report a case of 76-year-old woman with a rare variant of chromophobe renal cell carcinoma (CRCC). Cytologically, renal tumor cells obtained from imprint cytology were isolated or arranged in small or monotonous population cells with abundant granular cytoplasm. Neoplastic cells showed regular and uniformly shaped small round to oval nuclei with smooth margin. Binucleation was occasionally seen. Immunocytochemically, the cytoplasm of almost all tumor cells was diffusely positive for vimentin and CK 7. Histologically, the cytoplasm was abundant granular eosinophilic and composed of solid cell sheets or pseudoacinar structures. Additionally, tumor cells showed infiltration into some small renal veins covered by a single layer of endothelial cells. These cytological and histological features entirely resembled those of renal oncocytoma. We performed the analysis of von Hippel-Lindau (VHL) gene mutation, 3p loss of heterozygosity (LOH), and fluorescence in situ hybridization (FISH) on chromosomes 7, 10, 13, 17, and 21. As a result, we confirmed monosomy of chromosomes 7, 10, 13, and 17, and these findings corresponded to the diagnosis of CRCC. Finally, we present a case of renal tumor morphologically resembling renal oncocytoma but genetically showing CRCC. We suggest that oncocytic variant of CRCC may actually exist.