Not the most catchy of titles. The only reason for including this one at the moment is that it was an added complication to Matt’s particular cancer. The image is of ‘ordinary’ epithelial cells. [1]

Matt’s first pathology result included the following: -
“Microscopic Report
Viable tumour cells are seen which in places form pseudo-rosettes around vessels and are characterised by an anaplastic rhabdoid morphology with abundant refractile intracytoplasmic globules. Many of the cells show multinucleation and many also show very prominent amphophillic nucleoli. Small numbers of mature lymphocytes are scattered throughout the tumour, although this does not necessarily imply an origin from a lymph node …
… Vimentin is generally negative …
… These appearances are those of an undifferentiated malignant tumour with a rhabdoid phenotype …”

This was referred on for a second opinion which included the following: -
“Microscopic Description
A poorly differentiated round cell lesion composed by round polymorphic cells arranged in a solid pattern with geographic-type necrosis and numerous mitoses. The cells have a vesicular nuclei with large easinophilic nucleoli and a rhabdoid cytoplasm. The neoplastic cells strongly and diffusely express CD99, broad spectrum cytokeratins (MNF116) and low-molecular weight cytokeratins Cam 5.2 with a membranous and cytoplasmic stain. The other antibodies tested (CD34, vimentin, actin, desmin, Myf4, S100 protein and lymphoma markers) are negative.

Histopathological Opinion
A metastatic high-grade poorly differentiated round cell tumour with rhabdoid features expressing pan-cytokeratins. …”

Malignant Rhabdoid Tumours

Malignant Rhabdoid Tumours were first described as rare tumours of the kidney occuring in children of less than two years of age. The term ‘rhabdoid’ refers to the similarity in appearance under the microscope with cells found in Rhabdomyosarcoma. Subsequently, similar appearing tumours, were found in areas other than the kidney such as the central nervous system so the term ‘extrarenal’ was added.

Composite Extrarenal Rhabdoid Tumours

Later still cells with a rhabdoid appearance were found admixed with other cancer cells in a range of cancers in people of all ages. The ‘extrarenal’ tag is really superfluous and could be dropped. [2]

An unscientific search through the first 5 pages of results returned by Google with the phrase ‘Extrarenal Rhaboid Tumour’ found: -

So there is the strange situation where a whole variety of different tumours including some of unknown origin morph into cells with an appearance similar to those from a cancer occuring almost exclusively in childhood. They are also noted for being aggressive tumours.

Treatment

Having gone through all of the above, there is no real impact on the treatment where the recommendations when given are the same as for the primary tumour. In the case of unknown primary, the treatment would be as for unknown primary.

References

[1] Wikipedia Cell Culture
[2]INI1 expression and Composite Rhabdoid Tumours