World Health Organization Classification of Tumours Pathology and ...

cystic change may be seen. Solid, cordlikepatterns and sarcomatoid featuresmay be encountered. The sarcomatoidchange is a pattern of dedifferentiationsimilar to that seen in other types of renalcarcinoma {153}. The cells of collectingduct carcinoma usually display highgrade (Fuhrman 3 and 4) nuclear features.The cells may have a hobnail patternof growth and the cytoplasm is generallyeosinophilic. Glycogen is usuallyinconspicuous in collecting duct carcinoma.Both intraluminal and intracytoplasmicmucin may be seen.Some tumours with other morphologieshave been proposed as collecting ductcarcinomas. The most frequent oneshave a predominantly papillary growthpattern but they differ from usual papillarycarcinoma by a lack of circumscription,broad stalks containing inflamedfibrous stroma, desmoplasia, highnuclear grade and sometimes an associationwith more typical tubular patterns ofcollecting duct carcinoma elsewhere{2470}. The central location and associatedtubular epithelial dysplasia (atypia)are helpful in supporting a diagnosis,although dysplasia may be seen in collectingducts adjacent to other types ofrenal carcinoma.ImmunoprofileTumour cells usually display positivity forlow molecular weight and broad spectrumkeratins. High molecular weight keratins(34βE12, CK19) are commonlypresent and co-expression of vimentinmay be seen {2470}. There is variableimmunostaining for CD15 and epithelialmembrane antigen. The CD10 and villinstains are negative. Lectin histochemistry,usual Ulex europaeus agglutinin-1and peanut lectin are commonly positive.Table 1.05Diagnostic criteria for collecting duct carcinoma.Major Criteria- Location in a medullary pyramid (smalltumours)- Typical histology with irregular tubulararchitecture and high nuclear grade- Inflammatory desmoplastic stroma withnumerous granulocytes- Reactive with antibodies to high molecularweight cytokeratin- Reactive with Ulex europaeus agglutininlectin- Absence of urothelial carcinomaMinor Criteria- Central location (large tumours)- Papillary architecture with wide, fibrousstalks and desmoplastic stroma- Extensive renal, extrarenal, and lymphaticand venous infiltration- Intra tubular epithelial atypia adjacent tothe tumourDifferential diagnosisThe main differential diagnoses of collectingduct carcinoma include papillaryrenal cell carcinoma, adenocarcinoma orurothelial carcinoma with glandular differentiationarising in renal pelvis andmetastatic adenocarcinoma {2470}.ASomatic geneticsMolecular events that contribute to thedevelopment of collecting duct carcinomas(CDCs) are poorly understoodbecause only few cases have been analyzed.LOH was identified on multiplechromosomal arms in CDC, including 1q,6p, 8p, 13q, and 21q {2094}. Loss ofchromosomal arm 3p can be found inCDC {674,990}. High density mapping ofthe entire long arm of chromosome 1showed that the region of minimal deletionis located at 1q32.1-32.2 {2501}.One study suggested that 8p LOH mightbe associated with high tumour stageand poor patient prognosis {2335}. Incontrast to clear cell RCC, HER2/neuamplifications have been described inCDCs {2357}.Prognosis and predictive factorsThe typical collecting duct carcinomashave a poor prognosis with many beingmetastatic at presentation. About twothirdsof patients die of their diseasewithin two years of diagnosis {2470}.BFig. 1.41 Carcinoma of the collecting ducts of Bellini. A Tubulopapillary type of growth. B,C Note high gradecytological atypia.C34Tumours of the kidney