Characterization of poorly differentiated neoplasms can be a challenging task for the surgical pathologist. It is essential that the entire spectrum of immunomorphologic findings of various tumors be recognized to avoid improper characterization of a given neoplasm, which may in turn adversely affect patient management. Tumor characterization is complicated by the immunomorphologic transformations that malignant cells may undergo by virtue of which they may depart from expression of expected features and acquire new, unexpected characteristics. Traditionally, amelanotic melanomas have been difficult to characterize because of the diversity of their light microscopic morphology (epithelioid, spindle, and combined varieties). As a result, several other neoplasms are usually considered in the differential diagnosis. This report describes a primarily spindle-cell amelanotic melanoma that created a diagnostic dilemma, which could only be resolved by combining the information obtained from extensive evaluation by means of several diagnostic techniques. This case also stresses the phenotypic heterogeneity of the cytoskeleton of malignant melanomas and therefore their varied immunomorphologic characteristics.
This case report shows the importance of frozen section and/or permanent section pathology for diagnosis of tumorous conditions in patients with chronic osteomyelitis. According to published reports, a coincidence of malignant fibrous histiocytoma of bone and post-fracture osteomyelitis has occurred in only four patients. Our report details the treatment of 51-year-old man with a fracture 15 years previously and subsequent chronic osteomyelitis of the left distal femur. The original treatment was open reduction and casting. Fifteen years after the injury, the patient presented to the emergency room with increasing pain, erythema, swelling, and increased purulent discharge from the distal femur. Irrigation and debridement was done, but no frozen section or permanent pathology specimens were obtained. The left distal femur was radically resected for treatment of osteomyelitis. Histologic samples of the specimen revealed malignant fibrous histiocytoma of bone. A metastatic workup was negative. Subsequently, the left hip was disarticulated for wide resection of the tumor. One of two inguinal lymph nodes removed at that time was positive for malignant fibrous histiocytoma. The patient had additional chemotherapy. He was still alive 27 months after the operation.
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