Juxtacortical chondromyxoid fibroma in the small bones: two cases with unusual location and a literature review

Abstract

Chondromyxoid fibroma (CMF) is a rare, benign neoplasm of the bones, mostly affecting people in the second or third decade of life, with a slight male predominance. Long bones, especially the proximal tibia, are the most frequently affected sites, followed by the distal femur, pelvis, and small bones of acral sites [1,2]. The typical CMF eccentrically arises in the medulla of the metaphysis, with sharply circumscribed margins. Infrequent cases of juxtacortical subtypes have been documented in long bones, but only three of the short tubular bones have been reported in the English literature (Table 1). Here we present two new cases of juxtacortical CMF in the hand and foot, respectively. CASE REPORTCase 1A 43-year-old man presented with a swelling on the dorsum of the right foot for more than one year. He complained of intermittent pain for a few months. Plain films demonstrated a wellmarginated osteolytic lesion on the second metatarsal bone of the right foot (Fig. 1A). Magnetic resonance imaging (MRI) showed a 2 × 1.7 cm intracortical mass with expansile growth (Fig. 1B). Medullary bone was partially involved. T1-weighted images revealed an intermediate signal, while T2-weighted images showed a heterogeneous signal with some areas of high intensity. Preoperative diagnosis was a benign bone tumor such as simple bone cyst, and curettage with bone graft was performed.Histological examination of the lesion showed a lobular architecture on the low-power view (Fig. 2A). Lobules demonstrated hypocellular centers with hypercellular peripheries. Center of the lobules consisted of stellate or spindle-shaped cells with eosinophilic cytoplasmic processes in a myxoid background (Fig. 2B). Cellular areas in the periphery contained round cells with enlarged, hyperchromatic, and pleomorphic nuclei (Fig. 2C). Vacuolization was observed. The nucleocytoplasmic ratio of these cells, however, was low, and no mitosis was found, which implied degeneration rather than malignancy. Overall histologic features rendered a diagnosis of chondromyxoid fibroma. There has been no recurrence for seven months after the surgery.