Soft tissue plasmacytoma

I was diagnosed with myeloma stage III IgG Kappa in 2001.
Link to Summary June 2001 to January 2009.
Last year May 2009 my IgG levels rose and I developed 2 soft tissue plasmacytoma in the skin on my skull. No pain, tenderness, headaches or discomfort just 2 lumps. A fine needle biopsy confirmed what they were.
Treatment was 4 months of cyclophosphamide and dexamethasone. This reduced the IgG back into the normal range and the two soft tissue plasmacytoma disappeared.
Unfortunately in November 2009 the two soft tissue plasmacytoma reappeared and a decision was made to treat them with radiation. IgG has risen slightly but staying within the normal range.
There will be 5 days of radiation started on Monday, a shallow blast allowing my brain cells to remain undisturbed. I will likely loose my hair permanently where the radiation is applied. Unlike chemotherapy where the hair grows back radiation kills the hair follicles.
Last week I had my two soft tissue plasmacytoma measured to create a template for a lead cover with a hole in it to be placed over my skull during radiation.
One soft tissue plasmacytoma is at the front of my skull, slightly to the left but still within the hairline measuring 5cm (2 inches) diameter by 2cm (3/4 inch) high.
The second is at the rear of my crown on the right hand side measuring 7cm by 5 cm (2-3/4 inches by 2 inches) and 1cm (3/8 inch) high.
There are two worrying aspects of my soft tissue plasmacytoma.
First is cosmetic. I am a 62 year old male with a reasonable crop of hair, receding a little and minor thinning on top. To suddenly have two large bald spots in 2 random places is a blow to my pride. Time for a deep breath, short hair cut, find new headwear other than a cap and move on.
Second is why is this suddenly happening to me and why on my skull? Is this a reaction to the accumulative effect of my treatment over the years? Will there be any more after these have been destroyed? Questions for my haematologist.

It has been difficult to find information on soft tissue plasmacytoma in the skull skin on the internet, the best I have found is here: Link to plasmacytoma overview.
Some notes from that link are:
Solitary plasmactomas can be divided into 2 groups according to location.
Plasmacytoma of the skeletal system (SBP) i.e. in the bones.
Extramedullary plasmacytoma (EMP) i.e. in the tissues outside of the bones.
Although extramedullary plasmacytoma (EMP) can occur in any site, 80-90% of tumours develop in the head and neck area, especially in the aero digestive tract.
Three fourths of extramedullary plasmacytoma (EMP) cases involve males.
Based on the documented radiation sensitivity of plasma cell tumours, the accepted treatment is radiotherapy.