A 30-year-old woman with history of developmental delay, cognitive disability, seizure disorder, and multiple renal masses, status post right partial nephrectomy for neoplasm, was evaluated for a newly found renal mass. CT showed a 2.2 cm enhancing mass in the left kidney. Fine needle aspiration and core biopsy of the new left kidney lesion were performed and the findings are shown on Figure 1.
The correct answer is ...
Figure 1 shows cytology specimen (A, B) and biopsy (H&E, C, D) of a renal cell carcinoma with fibromyomatous stroma (previously known as Tuberous sclerosis-associated papillary RCC ). Histologically, this entity is characterized by elongated branching tubules or papillary structures composed of cells with distinct cell membrane, abundant clear cytoplasm, and prominent smooth muscle and fibromatous stroma (1). Immunohistochemical profile is characterized by reactivity to PAX8, CD10, CK7, CAIX (Fig.1 E,F), and molecular analysis revealed TSC/MTOR mutations but lack of VHL or chromosome 3p alterations. This neoplasm has indolent behavior.
Tuberous sclerosis complex (TSC) results from germline loss-of-function mutation in either TSC1 (9q24) or TSC2 (16p13). The majority of new cases are due to de novo mutations in TSC genes. It is inherited as autosomal dominant disease. Patients are at risk for renal cell neoplasms, which occur with female predominance and at younger age (2). Angiomyolipomas are one of the major features of TSC (3) and often occur as bilateral multifocal lesions (4,5). The most common types of renal cell carcinoma seen in patients with TSC include eosinophilic solid cystic renal cell carcinoma, renal cell carcinoma with fibromyomatous stroma, and hybrid oncocytic/chromophobe tumor (1).
Clear cell renal cell carcinoma is incorrect: Clear cell renal cell carcinoma is associated with von Hippel–Lindau disease.
Metanephric adenoma is incorrect: Metanephric adenoma consists of small, basophilic tubular epithelium arranged in tubules, glomeruloid structures, papillae, or exhibit solid growth pattern. It is positive for WT1 and CD57, and molecular studies reveal BRAF V600E mutation in up to 90% of the cases. These are often associated with polycythemia vera (6).
Congenital mesoblastic nephroma is incorrect: Congenital mesoblastic nephroma is the most common renal neoplasm diagnosed in infancy. Genetically it is characterized by trisomy 11 and t(12;15) leading to fusion of ETV6 and NTRK3 (7).
Krasimira Rozenova, M.D., Ph.D.
Resident, Anatomic and Clinical Pathology
Diva Salomao, M.D.
Consultant, Anatomic and Clinical Pathology
Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science