Solitary plasmacytoma of bone
They are found in the bone marrow of the axial skeleton or long bones of limbs. It is most commonly found in the thoracic vertebrae but can also be seen in following order in other vertebrae - lumbar, sacral, and cervical vertebrae . In approximately 20% of the cases involvement of other bones like rib, sternum, scapula, or clavicle have also been reported .
The signs and symptoms are:
Extramedullary plasmacytomas occur outside the bone marrow and therefore can be found anywhere in the body. Although about 80-90% are usually seen in head and neck with high predisposition for upper respiratory tract and oral cavity.
The signs and symptoms are:
It is important to differentiate SBP and EMP from multiple myeloma. Multiple Myeloma exhibit increased calcium levels, renal insufficiency, anemia and lytic bone lesions-CRAB which are absent in SBP and EMP.
After a thorough history taking and physical examination, the following tests are ordered for further analysis:
Skeletal surveys are helpful in SBP. A solitary bone lesion is diagnostic of SBP which is confirmed by biopsy that shows plasma cell infiltration in bone marrow (in a normal bone marrow <10% of plasma cells are seen) and no systemic involvement .
EMPs are diagnosed on basis of tissue biopsy. Histologically presence of monoclonal plasma cells and plasma cell infiltrates <5% are features of EMP. Absence of lytic bone lesions, systemic involvement, anemia, high calcium levels helps in ruling out multiple myeloma  .
According to the Durie and Salmon staging system, solitary bone plasmacytoma are classified as Stage I myeloma . To classify a SBP as Stage I myeloma it should fulfill all the following features: a hemoglobin less than 10 g/dL, normal serum calcium levels, normal bone structure or solitary plasmacytoma only, and low M-component (IgG < 5 g/dL, IgA < 3 g/dL, urine light chains < 4 g/24 h) .
The gold standard treatment for SBP and EMP is radiotherapy . This therapy focuses only on the tumor and thereby kills only the abnormal cells causing less damage to other normal healthy cells. This is helpful in solitary plasmacytomas since they are localized making radiation as the best and easy approach. Recurrences are still reported and plasmacytomas tend to progress to myeloma. This therapy is continued over several days to reduce side-effects.
In cases of myeloma chemotherapy maybe considered. Depending on the case and risk profile either a combined approach of chemotherapy and radiation or single treatment modality is employed. SBP tend to progress to myeloma. If evidence of skeletal instability is found, surgery is done to reduce the risk of fracture and radiation is delayed though surgery is very rare.
The drugs used in chemotherapy in myleoma are mephalan, cyclophosphamide, doxorubicin. Corticosteroids like prednisolone and dexamethasone are also used. Recently newer drugs have been on the rise-thalidomide, pomalidomide, lenalidomide, bortezomib and carfizomib. Stem cell transplant are kept as last resort.
All patients require life long follow up. A regular PET scan or MRI are advised for initial five years post treatment along with blood and urine tests.
Plasmacytoma has varying prognosis. The prognosis of multiple myeloma is determined by knowing the type of plasmacytoma, the location and the extent of spread, staging of tumor, availability and responsiveness to treatment, patient and disease characteristics. About 65-84% of patients suffering from Solitary bone plasmacytoma have shown to progress to multiple myeloma as opposed to 11-30% of patients suffering from Extramedullary plasmacytoma at the end of 10 years. Cutaneous involvement is considered as poor prognosis. It is highly difficult to predict the prognosis of the disorder as it could either progress rapidly or remain asymptomatic for ages.
So far no specific cause can be pinpointed for the disease but exposure to radiation, industrial and airborne toxins are considered to contribute as risk factors.
Out of all the plasma cell disorders, Solitary plasmacytoma amount to 5% of all cases . It is commonly seen in blacks and is rare amongst Asian and Pacific Islanders. Men are twice more likely to develop the disorder than women. The incidence rate is 0.15 cases/100,000 (450 new cases per year). It is usually seen in the 5th and 6th decade of life.
7% of the patients exhibit extramedullary plasmacytoma at the time of diagnosis of multiple myeloma but not all progress. Only about 6% of the patients suffering from multiple myeloma progress to form extramedullary plasmacytoma after the diagnosis. Extramedullary plasmacytomas are commonly seen in association with people suffering from plasma cell leukaemia.
Plasmacytomas are abnormal cells that can be found at any location. Extramedullary plasmacytomas are seen in mucosal surfaces while solitary bone plasmacytoma is seen in bone marrow . Though they both are plasmacytomas, they differ in their neoplastic characters in terms of the overall survival rate, tumor growth and in location  . Histologically few authors comment that solitary bone plasmacytoma shows marginal cell lymphomas along with extensive plasmacytic differentiation. SBP and EMP may vary in their neoplastic features but share biologic features of other plasma cell disorders.
Genetic studies revealed losses and additions in different chromosomes. Continuous losses were expressed in chromosome 13, chromosome arm 1p, and chromosome arm 14q, while additions were exhibited in chromosome arms 19p, 9q, and 1q . Another important factor involved in progression of plasma cell disorders is Interleukin 6 (IL-6) .
Plasmacytomas are found in two forms:
There are various types of plasmacytomas:
Solitary plasmacytoma are further classified into 2 types depending on the area where they are found:
EMP is a rare plasma cell tumor occurring in soft tissues. EMP is mostly seen in males during their 5th and 6th decades of life and predominantly seen in the upper respiratory tract. It has high affinity to the nasal cavity and parasnasal sinus.
EMP is commonly seen in tissues of throat and sinuses and has better prognosis. It is known to form 1% of heck and neck tumors and 3% of all plasma cell tumors. Histologically they are present in the submucosal layer and are highly destructive with high chances of local recurrence  .
SP is a type of plasmacytoma that shows no systemic involvement and is limited to bone or soft tissue. The cells are neoplastic and monoclonal in origin. It commonly affects the axial skeleton; for e.g. cranium, vertebra  .
Plasmacytomas are a mass of tumor cells that belong to the same cell lineage (monoclonal) that can be found in either the bone or soft tissue (extramedullary). They may present as single or solitary mass. Though it is a rare tumor, it later progresses to systemic disease and is considered as a singular counterpart of multiple myeloma.
There are two types of plasmacytomas: Solitary Bone plasmacytoma (SBP) and Extramedullary plasmacytoma (EMP). SBP are known to arise from the plasma cells in the bone marrow while EMP arise from plasma cells outside the bone marrow i.e from mucosal surfaces. SBP are seen in axial skeleton and long bones while EMP are seen in soft tissues of head and neck, nasal cavity and sinuses.
Pain at the site of tumor is one of the most common symptom of solitary bone plasmacytoma which occurs due to invasion of plasma cell tumor that destructs the bone. Extramedullary plasmacytoma present as nose bleeds, coughing up of blood, headache, difficulty to swallow, breathlessness and difficulty to talk.Though they belong to same group, they differ in their neoplastic features but are similar in their biological characteristics with other plasma disorders.
Multiple myeloma are lytic bone lesions characterized by punched out lesion and are well defined. They are associated with extra-pleural soft-tissue masses. In advanced plasmacytoma, massive erosion and destruction of the bone structure is seen that gives a “soap bubble” appearance.
Early administration of chemotherapy was used in various studies and thought to help in prevention and delay of plasmacytoma but in vain. Studies have discussed the use of adjacent chemotherapy to prevent the progression of myeloma.
It can be diagnosed by tissue or bone marrow biopsy which shows invasion of bone or tissue by monoclonal plasma cells. Various test are done to detect and monitor multiple myeloma. A full blood count to check levels of hemoglobin for anemia, low white blood cell count and low platelets on Complete Blood Count are seen. Lactic dehydrogenase (LDH), calcium, phosphorus, Erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) are all elevated. To check for kidney function, creatinine and urea levels are checked. Serum protein electrophoresis with immunofixation and urinary protein electrophoresis are also carried out. Skeletal bone surveys are done to look for lytic lesions (holes) and osteoporosis (hollow bones).
Radiation has remained the goal standard for treatment of SBP and EMP but in cases of myeloma chemotherapy is considered. If skeletal instability is seen surgical approach is taken to secure any potential risk for fractures but is very rare. PET scans, MRI scans are done every year for initial five years after treatment to keep a watch on any recurrences and progression of the disorder. Tissue biopsy, blood test and urine tests are conducted to rule out myeloma from SBP and EMP.