Contributed by Rosemary Recavarren, MD and Roy A. Frye, MD, PhD
The patient is a 41 year old gentleman who presented with a 2 week history of right sided "sharp and stabbing" rib pain without history of trauma or injury. The patient stated he felt a "snap" with a burst of pain in the right costal area, followed by inability to walk and could not breathe secondary to pain. His weight and appetite were stable prior to the incident. A chest CT scan revealed expansion of the cortex and medullary cavity of the right posterior 6th rib and a fracture with associated lytic focus in the posterior right 9th rib. The CT scan was interpreted as "hyperplasia/dysplasia" of the right 6th posterior rib and a pathologic fracture of the 9th posterior rib.
The patient's past medical history is significant for non-alcoholic steatohepatitis diagnosed 5 years ago by percutaneous liver biopsy. Family history is significant for systemic lupus erythematosus and type 2 diabetes in his mother and colorectal cancer in his father.
A CT guided biopsy was attempted, but was non-diagnostic. A diagnostic open biopsy was performed.
The specimen consisted of two curved segments of rib bone of 9.5 cm and 7.5 cm in length, corresponding respectively to the 6th and 9th ribs. There was a central bulging deformed region of 4.5 cm in the 6th rib and 3.5 cm in the 9th rib. In these areas the medullary bone was replaced with a very irregular tumor that revealed heterogeneous mixture of pale gray tan tissue.
Histologic features of the 9th rib biopsy are shown in the pictures below. The medullary cavity of the bone is replaced by clusters of intermediate size epithelioid cells with indistinct cytoplasmic borders and moderately abundant eosinophilic to clear cytoplasm. The nuclei of these cells are round to oval, and demonstrate irregular contours with numerous nuclear grooves. The clusters of epithelioid cells are admixed with large aggregates of eosinophils forming pseudoabscesses, as well as lymphocytes and plasma cells. The mitotic rate is 2/10 HPF.
Immunohistochemical stains demonstrate strong positivity for S100 protein and CD1a. The tumor cells fail to express pankeratin, leukocyte common antigen (LCA) and myeloperoxidase (MPO).
The 6th rib did not demonstrated presence of tumor cells on routine H&E original and recut sections or immunomarkers.