Case presentation: Pain in Left Knee

The patient is a very pleasant woman who is an active tennis player and 50 years of age. She has had aching pain in the left knee and a radiograph revealed a bone lesion in the proximal tibia. The patient is seen at the request of her orthopedic surgeon.

The patient is generally healthy. She is currently taking no medicines. There is no family history of bone lesions or bone tumors.

On detailed examination, the patient is in no acute distress, and is oriented to time, place, and person. Examination of the right knee shows normal appearance. There is no effusion. There is no erythema or swelling, no ecchymosis or bruising noted. The alignment of the knee is normal. The range of motion is full.

In the proximal tibia there is no mass palpable. There is no tenderness over the proximal bone. There is no erythema or sign of inflammation. There is no popliteal adenopathy, no inguinal adenopathy, and no cervical adenopathy. The skin is normal and there is no cafe au lait spots.

Radiographs and MRI are available for review.

There is a well defined lesion in the proximal tibia that has a partially complete sclerotic rim. It reaches up to but does not appear to involve the left knee joint. It has multiple loculations but there is no definite internal calcification. There are no rain or arc patterns of popcorn or cartilage.

The MRI does not add to the diagnostic information. It identifies the lesion and rules out exta- osseous mass. There is irregularity of the posterior cortex as it lays adjacent to the tumor, but there does not appear to be any breach of the cortex nor is there any tumor outside the bone. The borders on the lesion on MRI are less distinct than would be expected given the x-ray appearance alone. There is a fading border that appears to meld imperceptibly with the surrounding bone in many areas.

Diagnosis:

This tumor has been given the names benign fibrous hystiocytoma, fibrous histiocytoma, xanthofibroma, fibroxanthoma of bone, and primary xanthoma of bone. The author of this site prefes the name benign fibrous histiocytoma.

There is disagreement amongst pathologists as to whether this tumor represents a true neoplasm, adevelopmental defect, or a reactive process. A portion of the confusion arises from the lack of agreement between pathologists as to what exactly defines this lesion. Different pathological, clinical and radiographic definitions of this lesion have led to different findings of frequency, age range, location in the skeleton, histological appearance, and tumor behavior. The authors of this site have combined information from a number of sources to create this summary. For additional information please refer to the primary sources listed in the references section.

Clinically, patients report pain from the lesion, often of months or years duration. Pain may be associated with pathological fracture. There may be some local tenderness, but no swelling or mass is seen, and there are no systemic symptoms. There it is normally no impairment of the function of the nearby joint.

In some cases there is a primary underlying disorder of cholesterol metabolism or other lipid abnormalities. In these cases the lytic bone lesions are analogous to those seen in storage diseases such as Gaucher's disease. These multiple lesions are termed "xanthoma disseminatum". One reported case is of a 10 year old boy with lytic lesions in the pelvis, femur, and humerus, as well as yellow and brown papules and plaques on the face and trunk. This patient also had polyuria and polydipsia, and was found to have diabetes insipidus. (Khandpur)

Laboratory studies are not helpful.

Radiographically, the lesion occur commonly in the ribs, pelvis, including the sacrum and ilium, or in the epiphysis or diaphysis of tubular bones. These tumors have been reported in the jaw and associated soft tissues. In another report this tumor occurred commonly around the knee. It has a lytic, loculated appearance with prominent sclerosis of the edges of the lesion. There is no matrix mineralization. The zone of transition of the lesion is narrow. Cortical expansion and soft tissue invasion are rarely seen. The tumor may resemble non-ossifying fibroma, except that the patients are older and have pain, and these lesions have more promenent marginal sclerosis. Some authors have report a periosteal reaction, but others do not. There is prominent marginal sclerosis which may have the appearance of periosteal reaction in lesions that are juxtacortical.

CT scan shows a moderately irregular lytic area with an prominent trabecular pattern and surrounding sclerotic bone.

On MRI scans, there is central low signal intensity with a surrounding rim of high signal on T1, and more uniform but somewhat varigated high signal intensity on T2 sequences, with the surrounding sclerotic bone having low signal intensity.

On bone scan, the lesion has been reported to have no uptake, but the author cannot confirm this.

On gross examination, the tumor tissue consists of a mixture of firm but unmineralized yellow-tan tissue and partially hemorrhagic red-brown tissue. The yellow-tan tissue contains predominantly xanthic material. Histologically , the tumor consists of fibroblasts and mononuclear or multinucleated cells that have the appearance of histiocytes. The tumor may contain large areas of "foam cells", lipid-filled cells with abundant vacuolated cytoplasm, interspersed with small fibrovascular septations, as well as masses of cholesterol. No mitotic activity, cellular atypia, or pleomorphism is present. In one review (Bertoni) giant cells were found in 21 of 21 cases, where as other pathologists believe that there are normally no giant cells or an occasional multinuceated giant cell in these tumors. The cells are negative for S100 and positive for anti-human macrophage marker HAM-56, which indicates hystiocyte lineage.

Treatment consists of careful and complete curettage and filling of the defect with graft material, bone cement, or other suitable bone void filler. The risk of recurrence is variable depending on which series is consulted. In one series, (Clarke) 3 of 8 cases recurred locally, and two required amputation. In the Bertoni series, none of the 21 cases had local recurrence.

If you have been diagnosed with this lesion or have treated a lesion of this type, we are interested in seeing high-quality digital photos of the imaging studies and related material for our study and for addition to our site. Please contact us.

Bertoni at al, Am J Clin pathol., 1988;90 377-384

Clarke et al, Am J Surg Pathol., 1985;9:806-815

Macdonald, Arch Pathol Lab Med. 2002;126:599-601

Khandpur et al, Aus J Dermatol., 2003;44:190

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