Clear Cell Renal Cell Carcinoma With Extensive Osseous Metaplasia: Report of a Rare Case

Primary osteosarcoma of the kidney: A case report

Primary renal osteosarcoma is an exceedingly rare subtype of renal malignancy, noted for its aggressive nature and often fatal outcome. The scarcity and severity of this condition have resulted in a dearth of reliable methods for early diagnosis and effective treatment. The present article contributes to the existing body of knowledge by presenting a comprehensive clinical case of a 46-year-old male patient with primary renal osteosarcoma. The detailed analysis of the clinical features, imaging characteristics, treatment approaches and prognosis of the patient in the present case aimed to enhance the understanding of renal osteosarcoma and inform clinical decision-making. The patient initially presented with painless hematuria, and further diagnostic work-up, including imaging and pathology, confirmed the diagnosis of primary renal osteosarcoma.

A very rare case of bone metaplasia of renal cyst: A case report

INTRODUCTION

Renal Osseous Metaplasia (OM) is a rare condition in which mature bone forms within the renal parenchyma, typically as focal cortical lesions. Although it is usually considered a spontaneous and less pathologically significant lesion, it has been observed in damaged renal allografts and other urinary tract sites. The case we present involves a native kidney with a simple renal cyst, where histopathological examination post-tumor enucleation revealed OM, emphasizing its noteworthy presence in clinical settings.

CASE PRESENTATION

A 37-year-old female with a history of cesarean delivery and recent emergency surgery presented with abdominal and left flank pain. Initial ultrasound revealed a 4.2 cm anechoic cyst in the lower pole of the left kidney, which was confirmed by abdominal computed tomography (CT-scan as a well-defined fluid density cyst with a thick calcified wall. Surgical enucleoresection identified a Stoney hard mass with a unilocular cyst, histopathologically diagnosed as a simple renal cyst with metaplastic bone and hematopoietic elements. The patient had an uneventful postoperative course and remained well during the follow-up.

DISCUSSION

Osseous metaplasia (OM) involves extraskeletal bone formation and is associated with factors such as chronic ischemia and inflammation. While rare in renal pathology, it occurs in native kidneys, damaged renal allografts, and the urinary tract, posing radiological challenges in differentiating it from calcification. Accurate diagnosis requires histopathological examination because of the difficulties in distinguishing OM from calcification on imaging studies.

CONCLUSION

This case revealed Osseous Metaplasia in a simple cyst of the native kidney, urging vigilance in the diagnosis. While generally benign, its occurrence in damaged renal areas emphasizes its clinical significance, prompting further research. Heightened awareness and thorough examination are crucial for accurate diagnosis and patient management.

RENAL NEOPLASIA FROM A SINGLE POPULATION OF PTEROPODID BATS

Neoplastic diseases have rarely been reported in the family Pteropodidae, and primary malignant renal neoplasms are generally uncommon across animal species. This case series describes four cases of primary renal neoplasia: three renal cell carcinomas and one nephroblastoma in three species of pteropodid bats, specifically large flying foxes (Pteropus vampyrus, n = 2), straw-colored fruit bat (Eidolon helvum, n = 1), and a little golden-mantled flying fox (Pteropus pumilus, n = 1). Two of the cases were diagnosed antemortem using ultrasonography, computed tomography, and cytology; and one of these bats with a renal cell carcinoma was treated successfully with a unilateral nephrectomy. The remaining two cases were diagnosed at necropsy.

Clinicopathologic analysis of renal cell carcinoma containing Intratumoral fat with and without osseous metaplasia

BACKGROUND

There is minimal information regarding the prevalence of intratumoral adipose in renal cell carcinoma (RCC), and no study has assessed the impact of intratumoral adipose on the preoperative imaging diagnosis. The aim of this study was to investigate the prevalence and histopathologic characteristics of entrapped adipose with or without osseous metaplasia in RCC nephrectomy specimens and to determine if this finding impacted the preoperative imaging interpretation.

METHODS

704 RCC specimens were prospectively evaluated for entrapped adipose and osseous metaplasia (423 partial nephrectomies, 281 total nephrectomies; 327 pT1a, 377 ≥ pT1b; 510 clear cell, 119 papillary, 30 chromophobe, 22 clear cell papillary, 23 other). Imaging reports were obtained, and the presence of intratumoral fat or calcification and the radiologic diagnostic impression were recorded.

RESULTS

3% (n = 21) contained microscopically identified intratumoral adipose, with a similar frequency in the main histologic subtypes (p = 0.76). Mean metaplastic deposit size was 0.4 cm, mean deposit to capsule distance 0.2 cm, and 29% involved the tumor capsule. Histologically identified adipose was infrequently noted via imaging (13%), and only 1 case with histologically identified metaplasia had a radiologic diagnostic differential of angiomyolipoma (1/704, 0.1%).

CONCLUSION

While intratumoral adipose and/or osseous metaplasia can be observed within RCC, it is extremely rare for the radiologic diagnostic impression to have been confounded by histologically identified entrapped adipose. Awareness that metaplastic deposits are usually near the tumor capsule and may be minute could help prevent errors in diagnosis or staging.