Asian Cardiovasc Thorac Ann 2002;10:282-284
© 2002 Asia Publishing EXchange Pte Ltd
Plasmacytoma of the Rib in Young Male
Sara M George, MD,
Kamaraju S Ratnakar, MD,
Durjoy K Shome, MD,
Rajasekharan Nair, MCh1,
Abdulla Al Ajmi, FRCPA2
Department of Pathology
1 Department of Thoracic Surgery
2 Department of Haematology Salmaniya Medical Centre Bahrain
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For reprint information contact: Kamaraju S Ratnakar, MD Tel: 973 27 9517 Fax: 973 27 9649 Department of Pathology, Salmaniya Medical Centre, P.O. Box 12, Bahrain.
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ABSTRACT
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Solitary plasmacytoma of the 11th rib with soft tissue extension was seen in a 29-year-old male. Hematological and biochemical profiles did not reveal any systemic involvement. The 12-cm fusiform expansile lesion was excised and subjected to histopathological examination. The sections revealed sheets of plasma cells with focal cortical discontinuity and adjacent soft tissue invasion. This case is unique in view of the age of occurrence and the site of the lesion.
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INTRODUCTION
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Plasmacytomas are uncommon tumors of skeletal and soft tissues.1 Mass lesions composed of monoclonal plasma cells, without marrow involvement and with or without dysproteinemia, are considered determinants for the diagnosis of solitary plasmacytoma. Intraosseous plasmacytoma is often encountered affecting membranous bones, such as the vertebra, skull, and ilium, with the rib being a distinctly rare site.2 In view of its rarity and uniqueness in presentation, we report here a plasmacytoma of the rib in a young male.
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CASE REPORT
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A 29-year-old Bahraini male was admitted with a soft tissue mass in the region of the 11th rib with involvement of adjacent soft tissues towards the 10th rib region. Laboratory investigations included complete hemogram, routine blood chemistry, immunoglobulin profile, and urine analysis for cytology and proteins. The results are given in Table 1
. A trephine biopsy of the bone marrow along with aspiration revealed no abnormalities. The laboratory results were all within reference ranges, and no deviation from normalcy was noted on immuno-electrophoresis. Chest radiography revealed a cystic lesion in the right 11th rib with soft tissue extension up to the 10th rib. The 10th rib was free from any involvement. Skeletal survey revealed no other lesions nor osteopenia. Bone scan did not show any systemic disease.
The lesion in the 11th rib was excised and sent for histopathological examination. The 12-cm-long fusiform lesion (Figure 1) was subjected to several tests, including routine hematoxylin and eosin staining and immuno-histochemistry for 
and 
chains and immunoglobulins. On sectioning, the central 3-cm fusiform area was composed of an extremely soft gray tan lesion with thin cortical bone appreciable all around the lesion with focal points of discontinuity. The adjacent bone marrow showed normal spongy bone with red marrow and 2-mm-thick cortical bone. The central mass and adjoining normal marrow were studied. The lesion was highly cellular, composed of uniform round cells with scant stroma. The cells had large nuclei with chromatin clumping predominantly seen towards the nuclear membrane and abundant basophilic cytoplasm features characteristic of plasma cells (Figure 2). The nuclei in many cells were eccentric. There were many binuclear forms with scattered mitoses (2–5/10 high power field), as well as perinuclear clearing (a hof) in many cells. Immunohistochemistry revealed immunoglobulin G (IgG) with monoclonal chains. The morphological features were considered diagnostic of plasmacytoma of the rib.
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Figure 2. Photomicrograph showing uniform plasma cells with nuclear variations and binuclear forms (hematoxylin and eosin stain, original magnification x400).
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DISCUSSION
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Monoclonal proliferation of plasma cells may be encountered in both localized and disseminated forms.3 A systemic disease, multiple myeloma affects predominantly elderly males, with the highest incidence in the 7th decade.4 Multiple osteolytic lesions with or without generalized osteopenia, M-protein in the serum, and hypercalcemia constitute the constellation of clinical findings that characterize multiple myelomas.5 Marrow studies reveal diffuse or focal aggregates of immature plasma cells with immunologically demonstrable monoclonality of immunoglobulins and the light chains. While thoracic cage involvement either in the form of punched-out lesions or diffuse osteopenia is encountered in multiple myeloma, a mass lesion affecting an isolated rib is extremely uncommon. Hirai and associates6 reported solitary plasmacytoma of the 5th rib in a 72-year-old woman. They reviewed 17 cases of solitary plasmacytoma, all occurring in elderly individuals. The present case involving the 11th rib occurred in a 29-year-old male. Both solitary plasmacytoma and multiple myeloma rarely occur in individuals under 30 years of age. The highest incidence of solitary plasmacytoma is around the 6th decade, which is slightly earlier than multiple myeloma. Ishida and Dorfman7 documented 2 cases of plasma cell myeloma affecting the skull and ribs in a 23-year-old woman and the tibia in a 21-year-old male. In both cases, monoclonal immunoglobulins were found in the nonsecretory plasmacytoma, as in the present case. Meyer and Schulz2 in a review of 12 cases of solitary myeloma of bone recorded the involvement of the vertebrae, skull, and iliac bones but not the ribs.
Compared to the disseminated disease, the plasma cells in plasmacytoma are less mature with frequent binuclear and mitotic forms, as seen in this case. Immunocytochemical markers are undoubtedly diagnostic, showing light chain restriction with the predominance of immunoglobulin heavy chains, often IgG.8 In our case, demonstration of IgG along with chains assisted in the final diagnosis. Compared to multiple myeloma, solitary plasmacytomas have normal hemoglobin and calcium levels.4
A close follow-up is indicated in all cases of solitary plasmacytomas as nearly 35% of cases eventually will evolve into multiple myelomas. However, rib lesions are resectable, and the prognosis is good.
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REFERENCES
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ABSTRACT
INTRODUCTION
