Keywords

1 Definition

  • Fibro-osseous pseudotumor of digits (FPD) is a rare, benign, localized, self-limited fibro-ossifying process that occurs in the proximal phalanges of digits.

2 Synonyms

  • Florid reactive periostitis of the tubular bones of hands and feet

  • Parosteal fasciitis

3 Epidemiology

  • Predominant in females.

  • Adolescents or young adults.

4 Sites of Involvement

  • Proximal phalanges.

  • Metacarpal and metatarsal regions.

5 Clinical Symptoms and Signs

  • Pain.

  • Localized and fusiform swelling in hands and (less frequently) in feet.

6 Imaging Features

6.1 Radiographic and CT Features

  • Ill-defined and calcified soft-tissue mass without the zoning pattern of myositis ossificans (Fig. 65.1)

  • May present a radiolucent line between the calcified mass and the bone cortex.

  • Mature lesions are similar to myositis ossificans, becoming smaller and attached to the cortex.

Fig. 65.1
figure 1

(a) Roentgenograph of the proximal phalanx of the hand showing a dense soft-tissue mass with a periosteal reaction. (b) Sagittal MRI evidences the soft-tissue swelling and the periosteal reactive reaction of the phalanx

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6.2 MRI Features

  • Low or isointense signal mass in all sequences over the bone cortex and extensive peripheral edema.

6.3 Bone Scan Features

  • Hot spot

7 Imaging Differential Diagnosis

7.1 Parosteal Osteosarcoma

  • Densely ossified, juxtacortical, round or oval mass attached to the underlying cortex.

  • Rare in hands and feet.

8 Pathology

8.1 Gross Features

  • Less than 5 cm in diameter.

  • Stony consistency (mature lesion).

8.2 Histological Features

  • The lesion resembles myositis ossificans.

  • Lacks zoning phenomenon or zoning effect.

  • Loosely arranged fibroblasts on a myxoid matrix with abundant deposits of osteoid surrounded by active osteoblasts and multinucleated giant cells (Figs. 65.2, 65.3, and 65.4).

Fig. 65.2
figure 2

Microphotograph showing woven osteoid bone trabeculae rimmed by active osteoblasts. The bone marrow stroma is hypercellular, and some cells have a bizarre aspect

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Fig. 65.3
figure 3

Microphotograph showing a histology similar to the former image with the presence of multinucleated giant cells, osteoclastic type

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Fig. 65.4
figure 4figure 4

(a, b) Hypothenar eminence swelling with a red area in the skin. Note the small punctate scar lesion due to core needle biopsy, which was useful to make an accurate diagnosis. (c) Anteroposterior X-ray evidences a calcified mass in soft tissues close to the periosteal surface of the fifth metacarpal bone. (d) Evolution of the lesion 6 months later

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9 Pathologic Differential Diagnosis

9.1 Extraskeletal Osteosarcoma

  • More common in elderly patients, fifth and sixth decades.

  • Usually a high-grade tumor.

  • “Lacelike” osteoid.

9.2 Parosteal Osteosarcoma

  • Low-grade malignant tumor.

  • Extensive bone trabeculae formation with a tendency to parallel arrangement.

  • Fibrous stroma presents numerous spindle cells of low-grade sarcoma; similar to a low-grade fibrosarcoma.

  • Rare in the hands and feet.

10 Prognosis

  • FDP has an excellent prognosis.

  • Recurrence may be observed in cases treated in an early stage.

11 Treatment

  • Depends on the evolution stage of the lesion.

  • Excision of mature lesions is curative.