[427] Osteoblastic Osteosarcoma: Cytomorphologic Characteristics and Differential Diagnosis on Fine Needle Aspiration

Srividya Sathiyamoorthy, Syed Z Ali. Johns Hopkins Hospital, Baltimore, MD

Background: Osteoblastic osteosarcoma (OOS) is a uniformly fatal bone malignancy, if not diagnosed and treated appropriately in a timely manner. Fine needle aspiration (FNA) of osseous lesions is routinely performed in major medical centers. Appropriate characterization of the tumor will significantly influence the management and outcome.
Design: A retrospective search of the cytopathology archives of a large tertiary care center for a 22-year period (1989-2011) revealed 22 cases of OOS in 19 patients (primary-15, recurrent-5, metastatic-2). Material was obtained by FNA performed with radiologic assistance, except for one case for which the FNA was performed by the cytopathologist. Smears were stained with Diff Quik and Papanicolaou stains. Clinical outcome and histopathologic follow-up was reviewed and correlated.
Results: There were 11 males and 9 females (M:F, 4:3), ranging in age from 5-48 years (mean age 17.1 yrs). The anatomic locations were: distal femur (7), proximal humerus (2), proximal tibia (3), distal tibia (1), proximal fibula (1), iliac crest (2), pubis (1), sacrum (1), mandible (1) and soft tissue of thigh (3). All cases, except two, presented with progressively worsening localized pain, with or without swelling. The size of the lesions ranged between 1.8 cm to 34 cm (mean=8.9 cm). The initial FNA diagnoses were high grade malignant neoplasm (3), osteosarcoma, NOS (14) and OOS (5). Cytomorphologic characteristics were: variable cellularity, predominantly discohesive/single cells and small tissue fragments, focal osteoid, spindle to round plasmacytoid cells with moderate basophilic finely vacuolated cytoplasm, often with multiple cytoplasmic processes, round to oval nuclei with macronucleoli. 15/22 cases showed bi-nucleated and multi-nucleated osteoclast-like giant cells. Cases with high-grade histology displayed significant pleomorphism and abundant mitoses. Clinical outcome showed that eight patients had succumbed to the disease and 12 patients were alive at the time of this study.
Conclusions: An accurate FNA interpretation of OOS is significant, because immediate treatment is critical and the prognosis is better than other subtypes of osteosarcoma.
The differential diagnosis often includes reactive bone lesions and osteoblastoma.
The relative lack of significant pleomorphism and a larger population of plasmacytoid cells with fine cytoplasmic vacuolization are helpful distinguishing features.
A definitive diagnosis can often be made on FNA with clinical and radiological correlation.
Category: Cytopathology

Tuesday, March 20, 2012 11:00 AM

Platform Session: Section F, Tuesday Morning


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