Renal Medullary Carcinoma

Definition

High grade renal adenocarcinoma arising in medulla of the kidney, associated with sickle cell trait

In the past, some were included in collecting duct carcinoma
- Distinction may be largely clinical (see Differential Diagnosis at left)

Essentially every case associated with sickle cell trait or sickle cell disease
- Sickled cells may be seen in adjacent vessels
- Nearly all of African ancestry
Firm mass centered on the renal medulla
- Frequently extends into renal cortex and/or pelvis
Infiltrating sheets or cords of cells
- Frequent reticular/microcystic pattern
  - Spaces of varying size
  - Reminiscent of yolk sac tumor
  - May also have tubular and papillary patterns
- Dark eosinophilic granular cytoplasm
- Intralumenal mucin frequent
- Extra-renal and vascular invasion frequent
Rhabdoid pattern may be seen
- INI1 negative (all patterns)
Prominent stromal desmoplasia
- May be collagenous or myxoid
High grade nuclear atypia
- Pleomorphic vesicular nuclei with large nucleoli
- Frequent mitotic figures
- Frequent necrosis and hemorrhage
  - May form microabscesses
Renal medullary carcinoma is considered a separate entity from collecting duct carcinoma
- Considered by some reports to be a variant of collecting duct carcinoma
- Overlaps histopathologically with collecting duct carcinoma but is separated based on the following features
  - Occurrence in young patients
  - Association with sickle cell trait
  - Lack of INI1 expression (Cheng 2008) vs retention in 85% of collecting duct carcinoma (Elwood 2011)

John P Higgins MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates: 1/24/11, 6/17/12, 12/29/12