K.E.M.
Radiology
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Department of Radiology
Seth G.S. Medical College and K.E.M. Hospital, Mumbai , India
Case of the Month
Solitary plasmacytoma of the ilium
Contributed by: Chandrasekhar Khot
Clinical Profile:
A 55-year-old woman presented with pain in the left hip, inability to walk, tingling and numbness in the left lower limb since two months following a trivial trauma at home.
Radiological findings:
The radiograph of the pelvis with both hips shows an ill-defined, expansile lytic lesion in the left iliac bone involving the left acetabular roof. It shows few areas of tiny calcifications. (Fig. 1)
Fig. 1 : Radiograph of the pelvis with both hips shows an ill-defined expansile, lytic lesion in the left iliac bone involving the left acetabular roof.
Ultrasonogram of the left iliac fossa and pelvis (Fig 2a) shows a well-defined heterogeneously iso to hypoechoic lesion with few calcific foci. THe lesion measures 10 x 9cm. It shows vascularity with a PSV of 20 cm/s. There is bone erosion in the underlying left iliac bone(Fig 2b).
Fig. 2 : Ultrasonogram of the left iliac fossa and pelvis shows a well-defined , heterogeneously iso to hypoechoic lesion with vascularity (2a). There is lytic bone erosion in the underlying left iliac bone (2b).
CECT of the abdomen and pelvis (Fig 3) shows a large, permeative lytic lesion involving the left iliac blade, acetabulum, left sacral ala . There is a large heterogeneously enhancing soft tissue measuring 11x8x12 cm . There are multiple areas of cortical breach in the involved bones. Spiculated periosteal reaction is seen in the lateral aspect of the left iliac blade.
Fig, 3 : Axial, coronal and sagittal sections of CECT Abdomen and pelvis (3a to 3c-plain,3d to 3f-contrast, shows an extensive permeative lytic lesion involving left iliac blade, acetabulum, left sacral ala with surrounding large heterogeneously enhancing soft tissue. There are multiple areas of cortical breach in the involved bones with spiculated periosteal reaction.
MRI Pelvis with both hips (Fig 4) shows a well defined lobulated heterogeneously STIR hyperintense (Fig 4a), T1 hypo to isointense (Fig 4b) and PD hyperintense (Fig 4c and 4d) soft tissue lesion centered around the medial aspect of the left iliac blade. It shows heterogeneous enhancement on post contrast sequences. Inferiorly. it extends into the acetabular roof of the left hip joint causing irregularity of acetabular articular surface. Posteriorly , it reaches upto gluteus maximus muscle. Medially, the lesion obliterates the left sacroiliac joint and involves the adjacent sacral ala. The iliac vessels are correspondingly displaced.
Fig, 4 :Axial and coronal sections of MRI Pelvis with both hips shows a well defined lobulated heterogeneously STIR hyperintense (Fig 4a), T1 hypo to isointense (Fig 4b) and PD hyperintense (Fig 4c and 4d) soft tissue lesion epicentered around the medial aspect of the left iliac blade. It shows heterogenous enhancement on post contrast sequences(4e).
Whole Body FDG PET shows metabolically active, lytic bone lesion involving left pelvic bone and sacrum. Metabolically active lung changes are seen, likely of infective etiology.
Fig, 5 : Whole Body FDG PET shows metabolically active lytic bone lesion involving left pelvic bone and sacrum. Metabolically active lung changes are seen, likely of infective etiology.
Radiologiclal dignosis:
Based on imaging features, the differentials considered were:
• Plasmacytoma
• Malignant fibrous histiocytosis
• Metastases
• Ewings sarcoma
Pathological Dagnosis:
Sonography guided biopsy of the soft tissue lesion around iliac bone was done. Histopathological examination(Fig 6) shows a malignant tumour with plasmacytoid morphology. There is marked proliferation of sheets of small round lymphocytes with little cytoplasm, variable numbers of plasmacytoid lymphocytes, and well-developed plasma cells. On immunohistochemistry, the tumour cells express CD138 and MUM1; are weakly positive for CD20 and AE1/AE3. These features are suggestive of Plasmacytoma.
Bone marrow biopsy: shows normocellular bone marrow with 2% plasma cells.
Final Diagnosis:
Solitary bone plasmacytoma
Treatment:
The patient is currently planned to be initiated on chemotherapy and radiotherapy.
Fig. 6 : Histopathological examination shows malignant tumour with plasmacytoid morphology.
Timeline :
Discussion:
Solitary plasmacytoma (SP) is characterized by a localized accumulation of neoplastic monoclonal plasma cells without evidence of a systemic plasma cell proliferative disorder (1). They account for 3-6% of all plasma cell neoplasia. There is minimal or no systemic bone marrow involvement in contradistinction to multiple myeloma (2).
Types of solitary plasmacytomas have been described (3).
- Solitary bone plasmacytoma (approximately 70%)
- Extramedullary plasmacytoma (approximately 30%)