A 30-year-old male patient presented to our clinic with a history of tender swelling on the dorsum of middle phalanx of left index finger. The patient noted the mass since 12 months, which gradually became larger. The mass was 13 mm in diameter [Figure 1], with mild tenderness and firm in palpation, slightly mobile and, without marked movement on interphalyngeal motion, and no obvious adhesion to adjacent skin. The sensation of the finger was normal. Flexor and extensor tendons were intact; however, finger motion was slightly limited.
There was no history of major trauma, sharp injury, infection, or constitutional symptoms such as malaise, fever, or weight loss. Laboratory tests (CBC diff, ESR, CRP, Ca, P, Alk-P) were within normal limit. Tests for tuberculosis, brucella and syphilis were negative. Chest roentgenogram was normal.
Other imaging investigations included simple x-ray and CT-scan of the index finger. Conventional posteroanterior and lateral radiography revealed a paraosteal sclerotic lesion just abutting middle phalanx with bone density similar to adjacent bone and slight periosteal reaction [Figure 2], and further evaluation with CT-scan noted that the lesion has a patchy irregular border without cortical destruction or sauccerization and there is no typical zonal pattern in the lesion [Figure 3].
An excisional biopsy with dorsolateral incision was performed. The lesion was 1 x 1 x 1.5 cm in size, white-grayish in color, with hard consistency, and no adhesion to adjacent tendons or soft tissues. Histopathologic examination revealed proliferation of fibroblasts that are loosely arranged, a prominent myxoid matrix, and deposits of osteoid rimmed by uniform osteoblasts. Multinucleated giant cells were also existed [Figure 4].