A cystic nephroma, also known as multilocular cystic nephroma, mixed epithelial stromal tumour (MEST) and renal epithelial stromal tumour (REST), is a type of rare benign

Benign

A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...

 kidney tumour

Kidney tumour

Kidney tumours , also known as renal tumours, are tumours, or growths, on or in the kidney. These growths can be benign or malignant . They may be discovered on medical imaging incidentally Kidney tumours (or kidney tumors), also known as renal tumours, are tumours, or growths, on or in the kidney....

.

Symptoms

Cystic nephromas are often asymptomatic. They are typically discovered on medical imaging

Medical imaging

Medical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...

 incidentally (i.e. an incidentaloma

Incidentaloma

In medicine, an incidentaloma is a tumor found by coincidence without clinical symptoms or suspicion. It is a common problem: up to 7% of all patients over 60 may harbor a benign growth, often of the adrenal gland, which is detected when diagnostic imaging is used for the analysis of unrelated...

).

Diagnosis

Cystic nephromas are diagnosed by biopsy

Biopsy

A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...

 or excision. It is important to correctly diagnose them as, radiologically, they may mimic the appearance of a renal cell carcinoma

Renal cell carcinoma

Renal cell carcinoma is a kidney cancer that originates in the lining of the proximal convoluted tubule, the very small tubes in the kidney that filter the blood and remove waste products. RCC is the most common type of kidney cancer in adults, responsible for approximately 80% of cases...

 that is cystic.

Pathologic diagnosis

The characteristics of cystic nephromas are:

• Cyst
  Cyst
  A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :* Acne...
  
  s lined by a simple epithelium with a hobnail morphology, i.e. the nuclei of the cyst lining epithelium bulges into the lumen of the cysts,
• Ovarian
  Ovary
  The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...
  
  -like stroma
  Stroma
  Stroma may refer to:*Stroma , the connective, functionally supportive framework of a biological cell, tissue, or organ**Stroma of ovary, a soft tissue, well supplied with blood, consisting of spindle-shaped cells with a small amount of connective tissue**Stroma of iris, fibres and cells in the...
  
   that has a:
  • Spindle cell morphology, and has a
  • Basophilic cytoplasm
    Cytoplasm
    The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
    
    .

Cystic nephromas have an immunostaining pattern like ovarian stroma; they are positive for:

• Estrogen receptor (ER)
  Estrogen receptor
  Estrogen receptor refers to a group of receptors that are activated by the hormone 17β-estradiol . Two types of estrogen receptor exist: ER, which is a member of the nuclear hormone family of intracellular receptors, and the estrogen G protein-coupled receptor GPR30 , which is a G protein-coupled...
  
  ,
• Progesterone receptor (PR)
  Progesterone receptor
  The progesterone receptor also known as NR3C3 , is an intracellular steroid receptor that specifically binds progesterone...
  
   and
• CD10.