PA27.8-17 | Renal Pathology II: Tubulointerstitial, Vascular & Neoplastic — Case Study

CLINICAL SCENARIO

A structured case-based assignment exploring the clinico-pathological workup of a patient presenting with painless haematuria and an incidental renal mass. You will work through the clinical presentation, imaging findings, urinary abnormalities, gross and microscopic pathology, diagnosis, staging, complications, and paraneoplastic manifestations — applying the core concepts of renal cell carcinoma (clear cell type, VHL pathway) covered in PA27.8–27.17.

Section 1 — Clinical Presentation and Differential Diagnosis

Analyse the presenting features of Mr. Kumar's case. What is the classic triad of renal cell carcinoma (RCC), and how many elements of this triad does this patient display? List three other diagnoses you must exclude when a patient presents with painless haematuria, and explain the clinical or investigative features that make each less likely here.

Guidance: Address: (a) classic triad definition and its frequency in modern presentations; (b) why painless haematuria in an older smoker must be considered malignant until proven otherwise; (c) differential diagnoses (e.g., transitional cell carcinoma of renal pelvis, renal angiomyolipoma, metastasis to kidney) with brief distinguishing features. Approximately 150–200 words.

Section 2 — Imaging and Urinary Findings

Interpret the imaging and laboratory findings in this case. What CT features favour a malignant renal mass over a benign cyst? Explain the significance of the renal vein filling defect seen on contrast CT. What additional urine investigation would you request to characterise the haematuria further, and what is its expected result?

Guidance: Cover: (a) Bosniak classification principles and CT hallmarks of RCC (hypervascularity, central necrosis, irregular margins); (b) tumour thrombus in the renal vein and IVC — its pathological mechanism (direct venous invasion), its impact on surgical planning, and its TNM staging implication; (c) urine cytology / urine for malignant cells — expected negative for low-grade lesions. Approximately 150–200 words.

Section 3 — Gross and Microscopic Pathology

Describe the expected gross and microscopic pathological findings of a clear-cell renal cell carcinoma (ccRCC) arising in the upper pole of the left kidney, as would be reported by the pathologist following radical nephrectomy. Include: gross appearance, histological appearance, immunohistochemical profile, and the molecular/genetic basis of ccRCC.

Guidance: Address: (a) gross — golden-yellow variegated cut surface, pseudocapsule, haemorrhage and necrosis, interface with renal sinus; (b) micro — sheets/nests of cells with clear cytoplasm (glycogen/lipid dissolved in processing), delicate sinusoidal vascular network, Fuhrman/WHO-ISUP nuclear grade; (c) IHC — CD10+, vimentin+, RCC Ag+, CK7−; (d) molecular — VHL gene (chromosome 3p25) biallelic inactivation → HIF-1α stabilisation → VEGF/PDGF upregulation → angiogenesis; relevance to targeted therapy. Approximately 200–250 words.

Section 4 — Diagnosis and TNM Staging

State the final pathological diagnosis for Mr. Kumar using the WHO classification. Apply the TNM (8th edition) staging criteria to this case, clearly identifying the T, N, and M categories. What is the overall stage, and what is its prognostic implication?

Guidance: Use: T3b (tumour thrombus in main renal vein or IVC below the diaphragm), N0 (no regional lymph node metastasis), M0 (no distant metastasis) → Stage III. Discuss: 5-year survival for Stage III (~53–60%); contrast with Stage I (<4 cm, organ-confined, ~81%); note that radical nephrectomy with thrombectomy is the standard treatment for T3b N0 M0. Approximately 100–150 words.

Section 5 — Paraneoplastic Manifestations and Complications

Mr. Kumar's serum calcium is 11.4 mg/dL and haemoglobin is 16.8 g/dL. Explain the pathophysiological mechanism underlying each of these paraneoplastic findings in the context of RCC. Name two additional paraneoplastic syndromes associated with RCC that are NOT seen in this case.

Guidance: Cover: (a) hypercalcaemia — PTHrP secretion by tumour cells (humoral hypercalcaemia of malignancy); distinguish from bony metastasis; (b) polycythaemia (erythrocytosis) — ectopic erythropoietin production by tumour cells → excess RBC production; note this is secondary (inappropriate) erythrocytosis; (c) two additional paraneoplastics — Stauffer syndrome (non-metastatic hepatic dysfunction) and hypertension (ectopic renin); mechanism of each. Approximately 150–200 words.

Section 6 — Disease Progression and Systemic Spread

If Mr. Kumar were to develop metastatic disease after nephrectomy, describe: (a) the two most common sites of RCC metastasis and the pathological mechanism of vascular spread; (b) the histological hallmark that distinguishes metastatic ccRCC at a secondary site; and (c) how the VHL–HIF–VEGF pathway underpins the rationale for targeted therapy with sunitinib or bevacizumab in metastatic RCC.

Guidance: Address: (a) lung (cannon-ball metastases) and bone (osteolytic, axial skeleton) — haematogenous spread via renal vein thrombus as conduit; (b) clear cells with delicate vascular network on histology — same as primary; (c) VHL loss → constitutive HIF-1α → VEGF overproduction → tumour angiogenesis → VEGFR TKIs (sunitinib) or anti-VEGF antibody (bevacizumab) block this pathway; also note mTOR inhibitors (everolimus) as second-line. Approximately 150–200 words.

PEER REVIEW

You will review two peers' submissions using the rubric provided. For each criterion: (1) assign a score from the rating descriptors; (2) write 2–3 sentences of specific, constructive feedback citing what the student did well and what could be improved (e.g., 'Your description of the VHL pathway was accurate, but the link to VEGF and angiogenesis was not explained — adding this would strengthen Section 3'). Avoid vague praise ('good work') or purely critical comments without guidance. Complete your reviews within 48 hours of submission. Your peer review quality will be assessed by the faculty tutor.