Lymphoma masquerading as infection.

During surgical training, medical students and residents constantly are reminded to culture every suspected tumor and send tissue for pathologic evaluation for every suspected abscess. A diagnosis of cancer can be missed easily if this procedure is not followed, delaying the diagnosis and possibly adversely affecting the patient's prognosis. The confusion also may be compounded by a sterile abscess, positive culture results or a negative biopsy specimen.

Giant cell tumors: inquiry into immunohistochemical expression of CD117 (c-Kit), microphthalmia transcription factor, tartrate-resistant acid phosphatase, and HAM-56.

Context: Osteoclast-like giant cells (GCs) in giant cell tumors (GCTs) are thought to derive from a monocyte-macrophage lineage. Microphthalmia transcription factor (MITF) is necessary for osteoclast gene expression and tartrate-resistant acid phosphatase (TRAP) activation; c-Kit plays a role in regulation of MITF.

Objective: To gain insight into the differentiation of GCTs of bone (GCTBs) and GCTs tendon sheath (GCTTSs) by investigating immunohistochemical staining for c-Kit, MITF, TRAP, and HAM-56 in the GCs and stroma.