Different types of kidney cancer grow at different rates, have different prognoses and react differently to treatment. BHD-related kidney cancer can be chromophobe, papillary or clear cell. Most of the tumours associated with BHD syndrome are either solely benign oncocytomas or oncocytomas mixed with a type of cancerous kidney tumour.
Chromophobe
Chromophobe kidney cancer is often slow-growing, and does not appear to metastasise in people with BHD syndrome. About 23% of BHD-related kidney tumours are chromophobe.
Papillary
There is not much research regarding BHD-associated papillary renal cancer. It is one of the two kidney cancer types that has been associated with the 5 known fatalities involving BHD syndrome (the other being clear cell, which is described below).
Clear cell
Although clear cell is one of the most common types of renal cell carcinoma, it is not common in families with BHD syndrome. Of the very small number of fatalities that have been associated with BHD, some were clear cell cases.
Oncocytomas
Oncocytomas are considered to be benign kidney tumours which can grow inside the kidney or on the surface. While benign, oncocytomas can damage the kidneys as they may grow in places that might affect kidney blood flow. Again, it is essential that a knowledgeable doctor is monitoring your kidneys.
It is not possible to know if a tumour is an oncocytoma until it is analysed by a pathology lab. The accepted practice is to remove all kidney tumours because they could be malignant. Only after a tumour is removed would you know that it is oncocytic.
This type of tumour does not metastasise, or spread, to other parts of the body. About 3% of BHD-related kidney tumours are classified as oncocytic.
Mixed or Hybrid Oncocytic tumours
Hybrid tumours are a mixture of two types, oncocytic and another type, and are common among BHD-related tumours. 67% of BHD kidney tumours are hybrid.
Kidney cancer classification, state and grade
If your kidney cancer is examined by a pathologist, you will be told the Stage and Grade, as well as its state.
- There are four stages, namely I, II, III, and IV.
In Stages I and II, the cancer is confined to the kidney; it has not spread to other organs or parts of the body. Most BHD-related tumours are Stage I or II. Stage I tumours are smaller than 7 centimetres (2.75 inches), while Stage II tumours are larger
Stages III and IV are used to designate cases where the cancer has metastasised (spread). Stage III cancers have spread to local organs; Stage IV cancers have spread to distant organs and tissues. Metastasis is rare in BHD syndrome.
- Grades are assigned a number from 1-4 and correspond to the growth rate of the cancer. Grade 1 tumours are the slowest-growing, while Grade 4 cancers are the most aggressive. A lower grade usually corresponds to a better prognosis. Research seems to indicate that BHD-associated renal tumours are slow growing.
There is also the classification of primary vs. metastatic.
-Primary tumours have grown from their cell of origin.
-Metastatic tumours originate from cancerous cells which have travelled to another part of the body.
The prognosis for BHD-related kidney cancer is, on the whole, positive. BHD-related cancers do not normally metastasise and so offer a good target for effective treatment.
