Focal Hematopoietic Hyperplasia of Rib: A Rare Pseudotumor and Review of Literature

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Primary tumors of the rib are uncommon, comprising 5%– 10% of all bony tumors. Benign tumors constitute 63% of this group. 1 Common benign entities include osteochondroma, en-chondroma, and fibrous dysplasia, while common malignant tumors of the ribs include plasmacytoma, chondrosarcoma, os-teosarcoma, and Ewing's sarcoma. 1 Focal hematopoietic hyper-plasia (FHH) is an unusual benign lesion characterized by an expansive osteolytic mass involving the rib in all reported cases. 2-4 Most cases were detected incidentally on routine chest radiography performed for unrelated reasons. The lesion is typically composed of hypercellular marrow containing all three lineages of hematopoietic cells with interspersed fatty marrow; no hematopoietic dyspoiesis or malignancy is seen. Though clinical signs and radiological features of the lesion often simulate a true neoplasm, in reality it is a pseudotumor. Follow-up investigation has failed to show any recurrence or neoplastic transformation after resection of the lesion. 2 To the best of our knowledge, to date only four cases have been reported in the English literature. 2-4 We report a case of FHH in the right second rib in a 26-year-old female who underwent surgery after radiological diagnosis of osteochondroma. A 26-year-old female patient presented with upper backache and pain in the right side of the neck for 2 months in duration. There was no history of trauma, tuberculosis, hypertension or diabetes. Physical examination, and hematological and biochemical investigation did not reveal any abnormalities. Routine chest radiography showed a well-defined, expansile sclerot-ic mass in the right second rib (Fig. 1A). Subsequent computed tomography revealed a 5.0×4.5-cm mass in the body of the rib with internal linear calcification. There was cortical bulging and thinning of the inner surface without cortical destruction (Fig. 1B, C). The patient underwent surgery with a radiological diagnosis of osteochondroma. The mass was completely excised, fixed in 10% buffered formalin and processed for paraffin embedding after decalcification in 5% nitric acid. Microscopic examination revealed an inner shell with essentially normal tra-beculae and a focal haphazard arrangement (Fig. 2A). Hypercel-lular marrow containing normal hematopoietic cells of all three lineages intermixed with fatty marrow in the inter-trabecular spaces was observed (Fig. 2B, C). No dyspoiesis or hematologi-cal malignancy was seen, nor was there any fibrosis. …