Angiomyolipoma with epithelial cysts (AMLEC): a rare but distinct variant of angiomyolipoma

TSC1 splicing mutation in renal angiomyolipoma with epithelial cysts without fat: A very rare case report and literature review

Renal angiomyolipoma is a benign mesenchymal tumor that can be divided into classical and other subtypes. Angiomyolipoma with epithelial cysts (AMLEC) is an extremely rare non classical subtype. AMLEC without fat component is even rarer. We report a case of AMLEC without fat in a 29-year-old man who was provisionally diagnosed with cystic renal carcinoma by ultrasonography, abdominal enhanced CT and MRI. He had no complaints, or personal or family history of TSC, or other malignancies. Based on imaging findings, robot-assisted laparoscopic nephron-sparing partial nephrectomy through a retroperitoneal approach was performed for the purpose of both diagnosis and treatment. We diagnosed AMLEC after considering the differential diagnosis of other cystic renal neoplasms, such as cystic renal carcinoma, multilocular cystic renal cell neoplasm of low malignant potential, adult cystic nephroma and mixed epithelium and stromal tumor. Meanwhile, the whole-exon sequencing (WES) results showed insert-splicing mutation in the 21st exon and 20th exon of the TSC1 gene. No treatments were performed after the operation and no evidence of recurrence or metastasis at regular follow-up.

Immunophenotypic analysis of angiomyolipoma with epithelial cysts, comparison to mixed epithelial and stromal tumors and epithelial and stromal elements of normal kidney and ovaries

Angiomyolipoma with epithelial cysts (AMLEC) is a rare variant of renal angiomyolipoma (AML). It is characterized by a conventional AML component admixed with epithelial cysts within an "ovarian-like" stroma. Mixed epithelial and stromal tumor (MEST) is another renal neoplasm featuring epithelial cysts and "ovarian-like" stroma. While there is consensus that in MEST the epithelial and stromal components are neoplastic, in AMLEC it has been hypothesized that the epithelial component may represent renal tubular entrapment or ovarian-like transdifferentiation of tumor cells. The aim of this study was to compare the immunophenotypes of the epithelial-stromal components of AMLEC and MEST, with normal kidney and ovary to provide additional insights into the pathogenesis and relationships of these entities. In this study, we analyzed eight cases of AMLEC and 14 cases of MEST from 2003 to 2023. We used tissue microarrays, full sections, or unstained slides with an immunohistochemical panel including renal and ovarian markers: SF1, ER, PR, AR, PAX8, WT1, GATA3, CA-IX, p16, inhibin A, and BCL2. We compared these cases with ten non-neoplastic ovary and kidney samples. Our findings indicate that the epithelial component of AMLEC and MEST resembles hormone receptor positive renal tubular epithelium (AR + /ER - /PR -). AMLEC's stromal component resembled hormone receptor positive renal stroma, while MEST's resembled ovarian stroma, supporting mullerian transdifferentiation. Our study showed that the epithelial and stromal components of AMLEC and MEST are immunophenotypically different and also differ from normal tissues. Our findings suggest that in AMLEC, the epithelial-stromal component represents a hormonally driven proliferation of non-neoplastic renal elements within a dysregulated tumor microenvironment.

Stealthy Encroachment: Unraveling an Encounter With Renal Myelolipoma

Myelolipoma of the kidney is an exceedingly unusual benign tumor of hematological components mixed with mature adipose tissue. We present a case of a 59-year-old male who presented with left flank pain and was found to have an atrophic left kidney on imaging studies. A computed tomography (CT) scan revealed a small and shrunken left kidney with an extrarenal pelvis. A diethylenetriamine pentaacetate (DTPA) scan results showed a total glomerular filtration rate (GFR) of 45.6 ml/min with a non-functional left kidney. The patient underwent a left nephrectomy, and a histopathological examination confirmed the diagnosis and highlighted the distinctive morphological features of this rare entity. Postoperatively, the patient experienced a complete resolution of symptoms. This case underscores the importance of considering myelolipoma in the differential diagnosis of renal masses and highlights the successful management of symptomatic cases through surgical intervention. Awareness of this rare tumor is crucial for accurate diagnosis and appropriate management. Further studies are needed to elucidate the natural history and optimal treatment strategies for renal myelolipomas.

TSC2 nonsense mutation in angiomyolipoma with epithelial cysts: a case report and literature review

Background

Angiomyolipoma with epithelial cysts (AMLEC) is an extremely rare subtype of kidney angiomyolipoma that contains epithelial-lined cysts. The most distinctive immunohistochemical feature of AMLEC is its immunoreactivity with melanocytic markers. AMLEC also has a distinct histological structure, which aids in its pathological diagnosis. To date 27 cases of AMLEC have been reported in 11 case series. However, the molecular biology underlying the pathogenesis of AMLEC remains unexplored.

Case report

A 30-year-old female was diagnosed with AMLEC and underwent partial nephrectomy. Histologically, the cross-section of cystic tissue revealed a multilocular appearance, with some cysts containing thrombus-like material, and the wall thickness was approximately 0.2 ~ 0.3 cm. Additionally, the compact subepithelial cellular stroma showed strong and diffuse nuclear labeling for estrogen receptor, progesterone receptor, and CD10, as well as HMB45 and Melan A, which are markers of melanocytic differentiation. Furthermore, using a DNA targeted sequencing panel with next-generation sequencing, we identified a nonsense mutation in TSC Complex Subunit 2 (TSC2) gene, resulting in the formation of a premature termination codon. Moreover, the mutated genes found to be enriched in the PI3K-AKT pathway. The patient in this case had a favorable postoperative follow-up at 3 months.

Conclusion

To the best of our knowledge, this study represents the first analysis of genotype mutations in AMLEC, providing valuable insights for future clinical practice. These findings have significant potential in guiding the understanding and management of AMLEC, paving the way for further research and advancements in the field.

Pathology of hereditary renal cell carcinoma syndromes: Tuberous sclerosis complex (TSC)

Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disease characterized by hamartomatous tumors involving multiple organs such as the brain, skin, heart, lung and kidney. TSC is caused by inactivating mutations in TSC1/TSC2, which encodes hamartin and tuberin, respectively, and forms a complex that regulates mechanistic target of rapamycin complex 1 (mTORC1), resulting in cell overgrowth and oncogenesis. Since a leading cause of morbidity and mortality in TSC relates to chronic kidney disease and the ability to preserve renal function, this review describes the important pathologic findings in TSC-associated renal neoplasms and their correlating sporadic counterparts. The most common renal tumor in TSC patients are AMLs, followed by a heterogeneous spectrum of renal epithelial tumors, which may provide clues to establishing a diagnosis of TSC.

Angiomyolipoma With Epithelial Cysts: A Rare but Distinct Variant of Angiomyolipoma

Renal angiomyolipomas, common benign tumors, can exhibit slow growth in sporadic cases or have aggressive tendencies when linked to genetic conditions like tuberous sclerosis. This case report focuses on the exceptionally rare angiomyolipoma with epithelial cysts (AMLEC) variant, particularly challenging to diagnose due to its scarcity. Describing a 41-year-old woman's case, initially suspected to be renal cell carcinoma during an infertility evaluation, subsequent partial nephrectomy revealed a tumor comprising smooth muscle, blood vessels, and fat, with cystic regions featuring cuboidal linings and a layer devoid of abnormal cell activity. Immunohistochemistry confirmed specific markers within different tumor components, highlighting the diagnostic complexities of AMLEC and emphasizing the crucial role of histopathological examinations in accurate characterizations.

Angiomyolipoma with epithelial cysts, an unexpected discovery in a gunshot abdomen: a single case report

Background

Angiomyolipoma with epithelial cysts is a rare variant of an angiomyolipoma that typically occurs sporadically. Patients with pre-existing kidney lesion or disease have significantly increased risk of morbidity and mortality associated with trauma. Abnormal and diseased kidneys are frequently injured by low or insignificant velocity impacts. The vulnerability of these kidneys is related to the type of pathology. However, cystic or hydronephrotic kidneys are more susceptible to trauma. Recent studies have shown an association of this rare entity with tuberous sclerosis complex. Despite the rarity of genetic association of Angiomyolipoma with epithelial cysts and tuberous sclerosis, the emerging findings raise the necessity of genetic testing of these lesions to confirm a remote possibility of tuberous sclerosis complex.

Case presentation

We report a case of a 38-year-old male patient who sustained a right renal injury as a result of a gunshot to the abdomen and underwent an emergency nephrectomy due to hemodynamic instability. A grossly looking shattered kidney was surgically removed. The morphology in conjunction with immunohistochemistry of the specimen favoured a diagnosis of Angiomyolipoma with epithelial cysts.

Conclusion

This is the first reported case of angiomyolipoma with epithelial cysts diagnosed on a nephrectomy specimen from renal trauma. We aim to highlight an approach to renal trauma on a kidney with pre-existing AMLEC as well as an approach to adult cystic renal neoplasms and to propose the importance of genetic testing for Tuberous Sclerosis.

Angiomyolipoma of the kidney-Clinicopathological analysis of 52 cases

The renal angiomyolipoma (AML) is a benign tumor characteristically composed of fat, smooth muscle tissue, and vessels. We collected AMLs from our nephrectomy database, reclassified them according to their histological appearance, recorded the demographic, clinical, and pathological parameters, and compared them with oncocytoma (RO) and renal cell carcinoma (RCC). Immunohistochemistry was ordered in 41 cases. In 2224 nephrectomies, we found 52 AMLs with a 53 mm median size. The mean age was 52.76. Forty-eight tumors were sporadic, while four were hereditary. The revision resulted in 31 classic, 13 leiomyoma-like, five lipoma-like, two epithelioid, and one AML with epithelial cysts. SMA was diffusely positive, except for the epithelioid type, while MelanA harbored stronger expression than HMB45. AML was more frequent in females and appeared ten and 7 years earlier than RO and RCC, respectively. The follow-up time was 7.42 years, and neither tumor-related death nor relapse occurred. AML is rare in nephrectomies and develops primarily in females in their 50s with an average size of 50-60 mm at the surgery. The histological appearance in order of frequency is classic, leiomyoma-like, lipoma-like, epithelioid, and cystic. The MelanA, HMB45, and SMA immunohistochemistry can support the light-microscopic findings.

Mixed Epithelial and Stromal Tumor: A Rare Renal Neoplasm-Case Report with Clinicopathologic Features and Review of the Literature

Mixed epithelial and stromal tumor (MEST) is a rare benign renal neoplasm composed of epithelial and stromal components. Here, we report a 61-year-old woman presenting with a left complex cystic renal mass. The lesion was found incidentally on ultrasound for abdominal discomfort. CT scan and MRI showed a 7.4 cm complex cystic lesion in the left kidney. The differential diagnoses included complex renal cyst and cystic renal cell carcinoma. Laparoscopic nephrectomy showed a large 7.5 cm multicystic tumor with thick and thin septae and smooth walled-cysts containing clear watery fluid. Histologic examination showed variable sized cysts lined by flattened, cuboidal to columnar epithelium with focal hobnailing. No significant cytologic atypia or mitoses were noted. The cyst lining epithelium was positive for CK7 and high molecular weight cytokeratin (34Be12). The stroma was positive for alpha smooth muscle actin, CD10, estrogen receptor, and progesterone receptor. This report contributes an additional case to our collective knowledge of these lesions and summarizes the literature around these rare neoplasms.

Spectrum of Presentations and Management Strategies in Renal Angiomyolipoma

Renal angiomyolipoma (rAML) occurs rarely sporadically but is commonly encountered in patients with tuberous sclerosis complex and lymphangioleiomyomatosis. rAML is a rare entity, not seen regularly in daily practice; however, is commonly encountered and diagnosed by clinicians who approach and treat kidney masses. Basic knowledge of this entity is necessary to recognize that despite being benign, these tumors can rarely cause deadly complications such as hemorrhage or severe renal dysfunction or may have malignant components associated with them.

Renal angiomyolipoma with epithelial cyst

Angiomyolipoma with epithelial cysts (AMLEC) is a recently described entity and is an uncommon subtype of kidney angiomyolipomas. AMLEC is a benign entity but usually masquerades a renal cell carcinoma on imaging examination. AMLEC has a distinct histological and immunohistochemical staining pattern, which helps in the pathological diagnosis. We present a rare case of AMLEC in a 26-year-old female, which was provisionally diagnosed as renal cell carcinoma on radiology. We also summarize the differential diagnosis of this rare variant, its characteristic features, and a review of the literature.

Myelolipoma of Kidney: A Rare Extra-Adrenal Tumor in an Unusual Site

Myelolipoma of the kidney is a very rare benign disease which is composed of mature adipose tissue admixed with mature hematopoietic elements in varying proportions. The most common location of myelolipoma is in the adrenal glands, but extra-adrenal myelolipomas in other locations such as the retroperitoneum, presacral region, pelvis, and mediastinum has also been reported. In this case report, we present a case of huge extra-adrenal myelolipoma in renal parenchyma which is rare site for its origin. We report a case of extra-adrenal myelolipoma occurring in the left kidney of a 46-year-old Indian man. We describe the radiological and clinicopathologic features of this unusual tumor with a review of the literature. This case is noteworthy because the tumor was very enlarged and its site was unusual. It is generally impossible to distinguish extra-adrenal myelolipoma from other retroperitoneal tumors by radiological imaging given the rarity of tumor more cases need to be reported to elucidate its biological behavior.

Radiologic features of mixed epithelial and stromal tumors of the kidney: Hyperattenuating on unenhanced computed tomography and T2-hypointensity on magnetic resonance imaging

In the 2016 World Health Organization renal tumor classification, the mixed epithelial and stromal tumor family was introduced as a new entity. This family encompasses a spectrum of tumors, ranging from predominantly cystic tumors (adult cystic nephromas) to tumors that are variably solid (mixed epithelial and stromal tumors). The majority of previous studies incorporating “mixed epithelial and stromal tumor” in the titles were actually reports of imaging findings of adult cystic nephroma. Thus, the solid component of mixed epithelial and stromal tumors has not been well evaluated. In this study, we present 2 cases of mixed epithelial and stromal tumors, as defined by the 2016 World Health Organization classification, showing a predominantly solid component. The characteristic findings of the solid component of these tumors were T2-hypointensity on magnetic resonance imaging and hyperattenuation on unenhanced computed tomography. Angiomyolipoma with epithelial cysts and epithelioid angiomyolipoma should be considered in the differential diagnosis of mixed epithelial and stromal tumors.

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.

Angiomyolipoma with Epithelial Cysts Masquerading as a Cystic Renal Cell Carcinoma

Angiomyolipoma with epithelial cysts (AMLEC) is a very uncommon renal tumor. AMLEC has a characteristic histological appearance and immunohistochemical staining pattern, knowledge of which should preclude misdiagnosis by pathologists. We present a rare case of an AMLEC which was suspected to be a cystic renal cell carcinoma radiologically. We describe the characteristic immunological staining pattern and ultrastructural features of this lesion and discuss the potential differential diagnoses.

Angiomyolipoma With Epithelial Cysts

Angiomyolipoma with epithelial cysts is a rare mesenchymal tumor of the kidney that enters in the differential diagnosis of adult cystic renal neoplasms. These tumors demonstrate a slight female predominance and can present either incidentally or with symptoms, commonly flank pain and hematuria. Unlike conventional angiomyolipoma, this variant is characterized grossly by both solid and cystic areas, and histologically by the presence of single or multiple cysts lined by epithelial cells, a subepithelial "cambium-like" layer of small stromal cells with a prominent capillary vasculature, and a thick exterior wall composed of poorly formed fascicles of smooth muscle and thick-walled dysplastic blood vessels. Tumors show a distinct immunohistochemical profile and are often reactive for melanocytic markers (HMB-45 and Melan-A), as well as estrogen receptor and progesterone receptor. These tumors have an indolent clinical course, with no reports of progression or metastasis in reported cases thus far.

Cysts in angiomyolipoma with epithelial cysts may be consisted of entrapped and dilated renal tubules: report of a case with additional immunohistochemical evidence to the pre-existing literature

Angiomyolipoma with epithelial cysts (AMLEC) is a distinctive variant of angiomyolipoma characterized by grossly apparent epithelial cysts and a cellular, müllerian-like subepithelial stroma. Some authors suspect that the epithelial cysts mainly represent dilated entrapped native renal collecting duct epithelium, while other authors think that they represented true epithelial differentiation of the AML. Recently, it has been reported that obvious immunolabeling of melanocytic markers such as Melan A and HMB45, which are often immunolabeled in classical angiomyolipoma, are present in epithelial cysts in cases of AMLEC. Here, we report the case of a 43-year-old Japanese woman with AMLEC, and attempt to elucidate the significance of melanocytic marker immunolabeling in the cyst's epithelium. In the present case, Melan A was labeled in the cyst's epithelium, and was thought to reflect its labeling in renal tubules existing in the renal parenchyma outside the tumor. This finding may indicate that the cyst epithelium is derived from entrapped renal tubules inside the AML. Non-immunolabeling of the estrogen and progesterone receptors in the cyst epithelium may also suggest that the cyst epithelium is not neoplastic, in contrast to their labeling in neoplastic cells existing in cyst wall. Further examination, such as molecular analysis, is needed to determine whether these epithelial cysts is neoplastic or non-neoplastic.

Renal angiomyolipoma with epithelial cysts: a rare entity and review of literature

Renal angiomyolipoma (AML) with epithelial cysts (AMLEC) is a comparatively rare benign renal tumor that is recently recognized as a distinct entity and there are relatively few reported cases in the English-language literature. To date 19 cases of AMLEC have been reported in 2 case series and a few case reports. AMLEC has been described as a cystic variant of AML. Herein we reported an AMLEC in a 25-year-old female patient, and to the best of our knowledge this is the first case report of AMLEC in Chinese. She was incidentally found to have a kidney-occupying lesion during a routine medical examination for 1 month. CT examination demonstrated a multilocular cystic lesions arising from right-kidney lower pole. The patient underwent the partial nephrectomy. Histological examination of the tumor was composed of epithelial cysts, compact subepithelial mullerian-like stroma and muscle-predominant AML. Immunohistochemically, epithelial cysts were positive for CK but negative for ER, PR, CD10 and HMB-45; the subepithelial stroma and muscle-predominant AML were positive for ER, PR and HMB-45; the subepithelial stroma was negative for SMA, but muscle-predominant AML was positive for SMA. The final histopathological diagnosis was AMLEC.

Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management

Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior. The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component. We review recent developments and provide a radiological classification of angiomyolipomas that helps physicians understand the various types and learn how to both diagnose and manage them.

Ten uncommon and unusual variants of renal angiomyolipoma (AML): radiologic-pathologic correlation

Classic (triphasic) renal angiomyolipoma (AML) is currently classified as a neoplasm of perivascular epithelioid cells. For diagnosis of AML, the use of thin-section non-contrast enhanced CT (NECT) improves diagnostic accuracy; however, identifying gross fat within a very small AML is challenging and often better performed with chemical-shift MRI. Although the presence of gross intra-tumoural fat is essentially diagnostic of AML; co-existing intra-tumoural fat and calcification may represent renal cell carcinoma (RCC). Differentiating AML from retroperitoneal sarcoma can be difficult when AML is large; the feeding vessel and claw signs are suggestive imaging findings. AML can haemorrhage, with intra-tumoural aneurysm size >5 mm a more specific predictor of future haemorrhage than tumor size >4 cm. Diagnosis of AML in the setting of acute haemorrhage is complex; comparison studies or follow-up imaging may be required. Not all AML contain gross fat and imaging features of AML without visible fat overlap with RCC; however, homogeneity, hyperdensity at NECT, low T2-weighted signal intensity and, microscopic fat are suggestive features. Patients with tuberous sclerosis often demonstrate a combination of classic and minimal fat AML, but are also at a slightly increased risk for RCC and should be imaged cautiously. Several rare pathological variants of AML exist including AML with epithelial cysts and epithelioid AML, which have distinct imaging characteristics. Classic AML, although benign, can be locally invasive and the rare epithelioid AML can be frankly malignant. The purpose of this review is to highlight the imaging manifestations of 10 uncommon and unusual variants of AML using pathological correlation.

Hepatic epithelioid angiomyolipoma with an unusual pathologic appearance: expanding the morphologic spectrum

Hepatic epithelioid angiomyolipoma (AML) is a rare lesion that is characteristically composed of a predominant or exclusive population of epithelioid cells coexpressing melanocytic and myogenic markers. The cystic variant of epithelioid AML is exceedingly uncommon. In this study, we present the clinicopathological features of a case of hepatic epithelioid AML with remarkable cystic degeneration in a 34-year-old female as well as with a literature review. A magnetic resonance imaging scan revealed a well-defined 30 cm × 25 cm hepatic mass. Sectioning of the well-defined mass revealed a non-encapsulated tumor that was multiloculated with amorphous necrotic tissue and hemorrhagic fluid. The inner cystic wall was rough and brownish-black in color. Microscopically, the tumor largely consisted of epithelioid cells that comprised approximately 95% of the total neoplastic components but also contained some spindle myoid cells, mature fat, and a thick-walled vasculature. Both intracellular and extracellular hyaline globules were frequently identified. Necrosis and invasive growth patterns were also present. By immunohistochemistry, spindle-epithelioid neoplastic cells were variably positive for Melan-A, HMB45, and SMA but were uniformly negative for epithelial and hepatocytic markers. This is the third report of a cystic AML in liver. The patient was followed for 71 months without any evidence of metastasis or recurrence.

Renal angiomyolipoma: a radiological classification and update on recent developments in diagnosis and management

Angiomyolipoma is the most common benign solid renal neoplasm observed in clinical practice. Once thought to be a hamartoma and almost always diagnosed by the imaged-based detection of fat, angiomyolipomas are now known to consist of a heterogeneous group of neoplasms. Although all are considered perivascular epithelioid cell tumors, many display different pathology, imaging features, and clinical behavior. The importance of understanding this group of neoplasms is emphasized by the fact that many types of angiomyolipoma contain little to no fat, and despite being benign, sometimes escape a pre-operative diagnosis. These types of angiomyolipomas can all be considered when encountering a renal mass that is both hyperattenuating relative to renal parenchyma on unenhanced CT and T2-hypointense, features that reflect their predominant smooth muscle component. We review recent developments and provide a radiological classification of angiomyolipomas that helps physicians understand the various types and learn how to both diagnose and manage them.

Renal myelolipoma: a rare extra-adrenal tumor in a rare site: a case report and review of the literature

Introduction

Myelolipomas are uncommon, benign tumors composed of mature adipose tissue and hematopoietic elements. They mostly occur in the adrenal glands, but extra-adrenal myelolipomas have also been reported in other locations such as the presacral region, retroperitoneum, pelvis and mediastinum. Here, we present a case of an extra-adrenal myelolipoma in a rare site: the renal parenchyma. To the best of our knowledge, it is only the third case reported in this unusual location.

Case presentation

We report a case of primary myelolipoma occurring in the kidney of a 55-year-old Moroccan man. We describe the radiological and clinicopathologic features of this unusual tumor with a review of the literature, and we discuss differential diagnosis of retroperitoneal myelolipomas.

Conclusion

This case is noteworthy because the tumor site was unusual. Although renal myelolipoma is rare, it should be considered in the differential diagnosis of lesions in this site.

Parapharyngeal liposarcoma: a case report

Background

Parapharyngeal liposarcoma is a very rare malignant tumor that often causes nonspecific clinical symptoms, such as progressive dysphagia, globus sensation and/or respiratory disturbances. The combination of radiological imaging techniques and histopathological analysis provides information for diagnosis; however, the pathogenesis is still uncertain.

Case presentation

A 30-year-old male patient presented with a pharyngeal cavity mass, which had been present for 2 years. The clinical syndrome included obstructive sleep apnea symptoms (i.e., respiratory disturbances, excessive daytime somnolence, and headache) and difficulty swallowing. The radiological examination (CT) demonstrated that there was a low-density irregular solid lesion on the posterior wall of the oropharynx and laryngopharynx, which descended to the superior mediastinum and extended to the left parapharyngeal space and sternocleidomastoid muscle. The boundaries of the lesion were clear, and the lesion’s density was nonuniform. Several septations inside the lesion were observed. The CT values of the lesion at the epiglottis and the vocal folds were 11 HU and minus 30 HU, respectively. After enhanced scanning, there was no apparent enhancement of the lesion: the surrounding tissue and blood vessels were squeezed and shifted, but the neighboring sclerotin of the cervical vertebrae was not invaded. The mass was removed via a transcervical approach, resulting in a complete amelioration of the patient’s symptoms. Interestingly, immunohistochemistry showed that the tumor cells expressed members of the B7 superfamily, including B7-H1, B7-DC and B7-H3. In addition, the expression of TIM-containing molecules, including TIM-3 and TIM-4, was observed.

Conclusions

CT and MRI demonstrated that the mass was a parapharyngeal liposarcoma. Furthermore, carcinoma-associated B7 and TIM-containing molecules were observed in the tissue, indicating that these molecules are most likely active in the pathogenesis of this disease.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1907794973876202

Cathepsin K expression in the spectrum of perivascular epithelioid cell (PEC) lesions of the kidney

The perivascular epithelioid cell (PEC) is a unique cell type coexpressing contractile proteins (mainly α-smooth muscle actin), melanocytic markers, including microphthalmia-associated transcription factor (MITF), and estrogen and progesterone receptors. It is constantly present in a group of tumors called PEComas. Renal PEComas include the common angiomyolipoma as well as less common lesions such as microscopic angiomyolipoma, intraglomerular lesions, angiomyolipoma with epithelial cysts, epithelioid angiomyolipoma, oncocytoma-like angiomyolipoma and lymphangioleiomyomatosis of the renal sinus. It has been demonstrated that most of these lesions are determined by mutations affecting genes of the tuberous sclerosis complex, tuberous sclerosis 1 (TSC1) and tuberous sclerosis 2 (TSC2), with eventual deregulation of the RHEB/MTOR/RPS6KB2 pathway, and it has been observed that some PEComas regressed during sirolimus therapy, an MTOR inhibitor. Recently, overexpression of MITF has been related to the expression of the papain-like cysteine protease cathepsin K in osteoclasts where it has inhibited MTOR. The aim of this study is to evaluate cathepsin K immunohistochemically in the entire spectrum of PEComa lesions in the kidney. The study population consisted of 84 renal PEComa lesions, including 5 composed predominantly of fat (lipoma-like angiomyolipoma), 15 almost exclusively composed of spindle-shaped smooth muscle cells (leiomyoma-like angiomyolipoma) and 31 common angiomyolipomas composed of a mixture of fat, spindle and epithelioid smooth muscle cells, and abnormal thick-walled blood vessels, 15 microscopic angiomyolipomas, 5 intraglomerular lesions, 2 oncocytoma-like angiomyolipomas, 8 epithelioid angiomyolipomas, 2 angiomyolipomas with epithelial cysts and 1 example of lymphangioleiomyomatosis of the renal sinus. In all of the renal PEComas, cathepsin K was found to be constantly and strongly expressed and seems to be a more powerful marker than other commonly used markers for their identification, especially to confirm the diagnosis on needle biopsies.

Renal angiomyolipoma: clinicopathologic study of 194 cases with emphasis on the epithelioid histology and tuberous sclerosis association

The majority of renal angiomyolipoma (AML) is sporadic and occasionally it occurs as part of tuberous sclerosis complex (TSC). Epithelioid AML (EAML), an uncommon variant, is considered potentially malignant based on anecdotal case reports. The prognostic significance of epithelioid component in an otherwise typical AML is uncertain. We studied 194 AMLs for the clinicopathologic features of epithelioid and TSC-associated AMLs. Epithelioid component was present in 15 cases (7.7%) with an average amount of 51% (range: 10% to 100%). Histologically, the epithelioid tumor cells were categorized into small, intermediate, and large cell type based on the cell size. Worrisome histologic features were seen in many EAMLs, including coagulative tumor necrosis in 27% (4/15), nuclear atypia in 93% (14/15), mitosis in 47% (7/15), and atypical mitosis in 1 case. All 15 EAML patients had a mean follow-up time of 5.1 years and none had local recurrence or distant metastasis. Sixteen (8.2%) AMLs occurred in patients with definitive TSC. Three histologic features, namely microscopic AML foci, epithelioid component, and epithelial cysts, were present in 10 (62.5%), 4 (25%), and 44% (7/16), respectively, of TSC-associated AMLs, compared with 11 (6.2%), 11 (6.2%), and 6 (3.4%), respectively, in non-TSC-associated AMLs (P value all <0.01). In summary, all 15 cases of EAMLs in our study had benign clinical outcomes despite adverse pathologic features. Epithelioid component, epithelial cysts, and microscopic AML foci are strongly associated with TSC and the presence of all 3 features should raise strong suspicion for TSC.

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.