Case 113 - Discussion

Uploaded: 2007-09-29, Updated: 2007-11-12

 


ELECTRON MICROSCOPY (WJH)
Ultrastructurally, the neoplasm consists of sheets of neoplastic cells containing round to ovoid nuclei many of which contain macro nucleoli with some chromatin clumping. These appear to be arranged in a vaguely acinar pattern. The cytoplasm of these cells contain dilated vesicles of varying diameter, many of which appear to contain lipid. There is some glycogen present and there is the paucity of other organelles. In other areas, the neoplasm consists of roughly rectangular cells arranged along the basement membrane in a vaguely acinar and papillary configuration. These cells contain large nuclei with prominent nucleoli and have abundant mitochondria and an occasional lipid granule. Some of these cells appear to have short, stubby microvilli and may represent the papillary carcinoma component of this neoplasm.

 

CYTOGENETICS REPORT
Cytogenetic analysis revealed the presence of an abnormal hyperdiploid clone characterized by additional copies of chromosomes 2, 3, 7, 12, 16, 17, 20 , and loss of chromosome 21. These findings are consistent with a clinical diagnosis of renal cell carcinoma.
NOMENCLATURE: 54,XX,+2,+3,+7,+12,+12,+16,+17,+20,+20,-21[20]

 

DIAGNOSIS

Mixed type I and type II papillary renal cell carcinoma.

 

Papillary Renal Cell Carcinoma

The Key Features

  • A fibrous capsule is almost always present;

  • Histology: two types of papillary RCCs and accumulation of lipid-laden macrophages in the stalk;

  • RCC+, CD10+, CK7+, Vimentin +/-;

  • Trisomy of chromosomes 7 and MET gene mutation;

  • Significant better prognosis than clear cell RCC.

CLINICAL FEATURES
 
  • Comprises 10-15% of RCCs.
GROSS FINDINGS
 
  • Well circumscribed mass in the renal cortex with a distinct fibrous capsule in most cases;
  • Cut surfaces: light gray to red-brown to golden yellow;
  • Intratumoral hemorrhage and necrosis are common.
MICROSCOPIC FINDINGS
 
  • Almost always surrounded by a fibrous capsule;
  • A single layer or pseudostratified layers of cells arranged on fibrovascular stalks. Collapse of the papillae and tubules may produce the impression of solid growth.
  • The cells of the papillary type of RCC can be basophilic, acidophilic, or clear.
  • Characteristically, accumulation of lipid-laden macrophages in the stalk that may greatly expand the papillary cores. The papillary cores can be thickened and hyalinized.
  • May see tumor necrosis and cholesterol crystals. Psammomatous calcifications may be abundant. Occasionally see sarcomatoid change and mucin secretion.
SUBTYPES
 
  • Type 1 Papillary RCC: comprise at least two thirds. The tumor is composed of small cells with scanty, pale, usually basophilic cytoplasm. The nuclei are small and ovoid with inconspicuous nucleoli and often prominent nuclear grooves (grades 1 and 2). The cells typically form a single layer on the papillae. Psammoma bodies and foamy macrophages are often abundant.
  • Type 2 Papillary RCC: comprise less than one third. The tumor is composed of large cells with abundant acidophilic cytoplasm. Apical cytoplasmic clearing can be present.  Nuclei are large and spherical with prominent nucleoli (grade 3). There is often focal pseudostratification of cells. The tumor cells may have intracytoplasmic lumens.
  • In those cases having an apparent mixture of the two types, classification is based on the predominant component
DIFFERENTIAL DIAGNOSES
 
  • Renal cortical adenoma: less atypia;
  • Metanephric adenoma: uniformly small epithelial cells forming very small acini. Scant cytoplasm, very basophilic. The tubules and papillae are tightly packed in an acellular stroma. EMA-, WT1+ and CD57+.
IMMUNOHISTOCHEMISTRY AND SPECIAL STAINS
 
  • RCC: >90% cases +;
  • Pancytokeratin and LMW CK: strongly positive, including CK7;
  • Positive for CD9 and CD10;
  • Vimentin: +/-;
  • Many tumors express parvalbumin and beta-defensin-1
  • HMW CK: negative
ELECTRON MICROSCOPIC FINDINGS
 
  • Luminal microvilli in variable size resting on a basal lamina;
  • The cytoplasm contains variable numbers of mitochondria;
  • Rare microvesicles or glycogen
CYTOGENETIC STUDIES
 
  • Sporadic papillary RCC: trisomy of chromosomes 7, 17, 12, 16, and 20; a germline mutation of the c-MET gene; and t(x;1)(p11.2;q 21) that results in a fusion of the TFE3 and PRCC gene;
  • Hereditary papillary RCC: germline mutation of the c-MET gene.
TREATMENT AND PROGNOSIS
 
  • Significantly better prognosis than clear cell RCC.
REFERENCES
 
  • Tumors of the Kidney, Bladder, and Related Urinary Structures. AFIP Atlas of Tumor Pathology - Fourth Series