Classification of Adult Renal Tumors: An Update

Myopericytoma/myofibroma as a stromal component of mixed epithelial and stromal tumor of the kidney: A case report

Mixed epithelial and stromal tumors (MESTs) of the kidney are rare renal neoplasms, primarily affecting middle-aged women. These tumors are characterized by a mix of epithelial and stromal components. While generally benign, MESTs require accurate diagnosis and appropriate management due to the potential for malignant transformation. The present study reports the case of a 75-year-old male patient who underwent a partial nephrectomy following the incidental discovery of a kidney tumor. Histopathological examination revealed a partially cystic tumor with solid areas, measuring 26 mm in diameter. The tumor had cysts lined with cuboidal cells and an ovarian-like stroma. The solid component consisted of elongated cells with eosinophilic cytoplasm and oval nuclei, showing angiocentric growth around small blood vessels without nuclear atypia or mitoses. Since the morphology of the solid component could not reveal the differentiation of those cells, immunohistochemical staining was performed and a myopericytoma/myofibroma component was established, mostly based on the positivity of smooth muscle actin, muscle-specific actin, h-caldesmon, estrogen receptor, progesterone receptor, solute carrier family 2 facilitated glucose transporter member 1 and collagen IV, along with a lack of staining for desmin, CD34, CD31 and CD99. Thus, to the best of our knowledge, for the first time in the literature, MEST with myopericytoma/myofibroma stromal component in a male patient was reported.

A first case report of primary epithelial myoepithelial carcinoma-like renal tumor showing a perivascular pseudorosette-like pattern: Description of morphologic, immunohistochemical, and genetic features

RATIONALE

Over the past decade, although several new entities of renal tumors have emerged, a form of renal cell carcinoma (RCC) that morphologically resembles epithelial-myoepithelial carcinoma has not been reported thus far. Herein, we describe a case of an unusual renal tumor that remained unclassified under a current RCC subtype, and briefly present its morphologic, immunophenotypic, and genetic features.

PATIENT CONCERNS

The patient was an 85-year-old man who presented with hematuria and flank pain. Imaging studies revealed a left renal mass without enlarged lymph nodes. There were no abnormal masses or nodules in other organs.

DIAGNOSES

The patient underwent no other treatment except the left radical nephrectomy under a clinical diagnosis of invasive urothelial carcinoma and was discharged on the thirteenth day. Histologically, the renal tumor showed biphasic proliferation of epithelial (strongly cytokeratin-positive; P63, P40, and vimentin-negative) and myoepithelial (strongly vimentin-positive; focal P63 and P40-positive; and weakly cytokeratin-positive) cells arranged in a perivascular pseudorosette-like pattern. No mutations were detected in multiple gene tests. According to the pathological structure, the patient was diagnosed as primary epithelial myoepithelial carcinoma-like renal tumor.

INTERVENTIONS

To the best of our knowledge, the present tumor has not been previously described, and thus, this variant has not been integrated into a known form of PCC. Therefore, we cannot diagnose this type of tumor with other types of kidney tumors.

OUTCOMES

Three years after primary diagnosis, the patient died of multiple organ failure result from multiple distant metastases.

LESSONS

We present the first case of carcinoma of the kidney with EMC-like features and a perivascular pseudorosette-like growth pattern. Clinicians should be aware of the features of this uncommon variant of RCC to avoid diagnostic delays or misdiagnosis and prevent unnecessary or inappropriate treatment.