The detection of hepatic nodules during follow-up of survivors of solid tumors in childhood raises a diagnostic dilemma. Focal nodular hyperplasia (FNH) is an uncommon, benign tumor and must be differentiated from late hepatic metastasis.

We retrospectively analyzed patients, treated for pediatric solid tumors between January 1990 and December 2007, and performed abdominal imaging as part of the follow-up.

Four survivors with FNH were detected, out of 450 who received chemotherapy with/out irradiation including patients who underwent autologous bone marrow transplantation (ABMT). Case 1: A 23 years(y) adolescent, presented at age 10y with acute abdomen due to embryonal sarcoma of liver, she received VACAIEx4, relapsed locally, and underwent ABMT with high-dose carboplatin/melphalan and radiotherapy. Asymptomatic multiple liver lesions were disclosed by US and MRI 5y later, biopsy proved FNH. Case 2: A 21y adolescent who at age 3y had alveolar rhabdomyosarcoma of the calf with positive inguinal nodes. She received VACAIE x6, and VP16/carboplatin x3 with local radiation. She developed ovary disorder and received oral contraceptive (OC) at age 14.5y, routine US 1.5y later disclosed nodular lesions in liver, diagnosed as FNH by CT, pills were stopped. At follow-up some lesions reduced in size and few disappeared. Case 3: A 9y old girl, operated for choroid plexus carcinoma at age 1.5y, received VP16/carboplatin x16 and underwent ABMT preceded by thiotepa/melphalan. Abdominal US at age 5.5y disclosed multiple liver lesions, biopsy proved FNH, that disappeared 2y later. Case 4: An 11y old girl operated at age 8 months for retroperitoneal germ cell tumor, received VIP/BVPx4, routine US at 10y disclosed 2 liver lesions diagnosed by CT as FNH.

We conclude that FNH can be differentiated from late metastasis by imaging; in questionable cases by biopsy, close follow-up is recommended, alkylating agents especially during ABMT, and OC may be risk factors.

Polyethylene wear debris in TKA arises from several sources, including the tibiofemoral articulation and the interface between the backside surface of the tibial insert and the metal tibial tray. In this study we identify a new source of abrasive damage to the polyethylene bearing surface: impingement of resected bony surfaces, osteophytes and overhanging acrylic cement on the tibial bearing surface during joint motion.

One hundred forty-eight tibial components of 24 different designs in a retrieval collection were examined. A digital image of the articular surface of each insert was recorded. The presence, location and projected area of abrasive wear to the non-articulating edges of the insert were assessed using image analysis software.

Significant abrasive wear was observed in 24% of the retrievals with cemented femoral components and 9% from non-cemented components. Of the retrievals exhibiting this abrasive wear mode, 46% experienced multiple site damage. The average damage area for each individual abrasive scar was 78±11mm^2. Within the group of worn inserts, the abrasive scars were seen with a frequency of 69% on the extreme medial edge, 19% on the extreme lateral edge, 38% on the posterior-medial edge and 23% on the posterior-lateral edge. In posterior stabilized components with an open femoral box design, scarring of the superior surface of the tibial post was also observed. This proposed mode of damage was confirmed with several retrieved femoral components containing either fixed cement protruding from the posterior condyles, from the medial and lateral edges or osteophytes embedded in the posterior capsule. The corresponding inserts exhibited significant abrasive scarring at those locations.

We have observed a previously unrecognized source of polyethylene damage resulting in gouging, abrasion and severe localized damage in cemented and uncemented total knee replacement. Clearly, acrylic cement, in bulk or particulate form, often contributes to severe damage of the tibial surface and improvements to instruments and techniques for cementing are needed to prevent this wear mechanism.