Differential diagnosis

Differential diagnosis

Mycetoma should be distinguished from Kaposi’s sarcoma, malignant melanoma, fibroma and foreign body (thorn) gran uloma. A radiograph that demonstrates the presence of bone destruction in the absence of sinuses is suggestive of tuberculo sis. The radiological features of advanced my cetoma are simi lar to those of primary osteogenic sarcoma. Primary osseous mycetoma is to be di ff erentiated from chronic osteomyelitis, osteoclastoma, bone cysts and syphilitic osteitis. In endemic areas the dictum should be ‘any subcutaneous swelling must be considered a m ycetoma until proven otherwise’. Moritz Kaposi , 1837–1902, Hungarian-born Professor of Dermatology viral cause was discovered in 1994. Ernest Codman , 1869–1940, American surgeon. Codman’s triangle can be seen in osteosarcoma, Ewing’s sarcoma, subperiosteal abscess and haematoma. Several imaging techniques are available to confirm the diag - nosis: plain radiography , ultrasonography , CT and magnetic resonance imaging (MRI). Plain radiograph In the early stages, soft-tissue shadows (often multiple) with calcification and obliteration of the fascial planes may be seen. As the disease progresses, the cortex may be compressed from the outside by the granuloma, leading to bone scalloping. Peri - osteal reaction with new bone spicules may create a sun-ray appearance and Codman’s triangle, not unlike an osteogenic sarcoma ( Figure 6.28 ). Late in the disease, ther e may be multi - ple punched-out cavities throughout the bone. Ultrasonography This can di ff erentiate between eumycetoma and actinomy - cetoma as well as between mycetoma and other conditions. In eumycetoma, the grains produce numerous sharp bright hyper-reflective echoes. There are m ultiple thick-walled cavi - ties with absent acoustic enhancement. In actinomycetoma, the findings are similar but the grains are less distinct. The size and e xtent of the lesion can be accurately determined ultrasonically , a finding useful in planning surgical treatment. - - - - - , University of Vienna, Austria, described pigmented sarcoma of the skin in 1872. The

Figure 6.28 Plain radiograph of the knee showing multiple large cavi

ties involving the lower femur, upper tibia and /f_i bula, with well-de /f_i ned margins and periosteal reaction typical of eumycetoma.

(b) Magnetic resonance imaging This helps to assess bone destruction, periosteal reaction and particularly soft-tissue involvement ( Figure 6.29 ) . MRI usually shows multiple 2- to 5-mm lesions of high signal intensity , which indicates the granuloma, interspersed within a low-intensity matrix denoting the fibrous tissue. The ‘dot-in-circle’ sign, which indicates the presence of grains, is highly characteristic. Computed tomography CT findings in mycetoma are not specific but are helpful to detect early bone involvement.

Granuloma Dot-in-circle sign Figure 6.29 (a) Magnetic resonance imaging (MRI) of the foot showing multiple lesions of high signal intensity, which indicates granuloma, interspersed within a low-intensity matrix, which is the /f_i brous tissue and the ‘dot-in-circle’ sign, which indicates the presence of grains. (b) MRI showing massive upper thigh and lower abdominal actinomycetoma.

Differential diagnosis

Mycetoma should be distinguished from Kaposi’s sarcoma, malignant melanoma, fibroma and foreign body (thorn) gran uloma. A radiograph that demonstrates the presence of bone destruction in the absence of sinuses is suggestive of tuberculo sis. The radiological features of advanced my cetoma are simi lar to those of primary osteogenic sarcoma. Primary osseous mycetoma is to be di ff erentiated from chronic osteomyelitis, osteoclastoma, bone cysts and syphilitic osteitis. In endemic areas the dictum should be ‘any subcutaneous swelling must be considered a m ycetoma until proven otherwise’. Moritz Kaposi , 1837–1902, Hungarian-born Professor of Dermatology viral cause was discovered in 1994. Ernest Codman , 1869–1940, American surgeon. Codman’s triangle can be seen in osteosarcoma, Ewing’s sarcoma, subperiosteal abscess and haematoma. Several imaging techniques are available to confirm the diag - nosis: plain radiography , ultrasonography , CT and magnetic resonance imaging (MRI). Plain radiograph In the early stages, soft-tissue shadows (often multiple) with calcification and obliteration of the fascial planes may be seen. As the disease progresses, the cortex may be compressed from the outside by the granuloma, leading to bone scalloping. Peri - osteal reaction with new bone spicules may create a sun-ray appearance and Codman’s triangle, not unlike an osteogenic sarcoma ( Figure 6.28 ). Late in the disease, ther e may be multi - ple punched-out cavities throughout the bone. Ultrasonography This can di ff erentiate between eumycetoma and actinomy - cetoma as well as between mycetoma and other conditions. In eumycetoma, the grains produce numerous sharp bright hyper-reflective echoes. There are m ultiple thick-walled cavi - ties with absent acoustic enhancement. In actinomycetoma, the findings are similar but the grains are less distinct. The size and e xtent of the lesion can be accurately determined ultrasonically , a finding useful in planning surgical treatment. - - - - - , University of Vienna, Austria, described pigmented sarcoma of the skin in 1872. The

Figure 6.28 Plain radiograph of the knee showing multiple large cavi

ties involving the lower femur, upper tibia and /f_i bula, with well-de /f_i ned margins and periosteal reaction typical of eumycetoma.

(b) Magnetic resonance imaging This helps to assess bone destruction, periosteal reaction and particularly soft-tissue involvement ( Figure 6.29 ) . MRI usually shows multiple 2- to 5-mm lesions of high signal intensity , which indicates the granuloma, interspersed within a low-intensity matrix denoting the fibrous tissue. The ‘dot-in-circle’ sign, which indicates the presence of grains, is highly characteristic. Computed tomography CT findings in mycetoma are not specific but are helpful to detect early bone involvement.

Granuloma Dot-in-circle sign Figure 6.29 (a) Magnetic resonance imaging (MRI) of the foot showing multiple lesions of high signal intensity, which indicates granuloma, interspersed within a low-intensity matrix, which is the /f_i brous tissue and the ‘dot-in-circle’ sign, which indicates the presence of grains. (b) MRI showing massive upper thigh and lower abdominal actinomycetoma.

Differential diagnosis

Mycetoma should be distinguished from Kaposi’s sarcoma, malignant melanoma, fibroma and foreign body (thorn) gran uloma. A radiograph that demonstrates the presence of bone destruction in the absence of sinuses is suggestive of tuberculo sis. The radiological features of advanced my cetoma are simi lar to those of primary osteogenic sarcoma. Primary osseous mycetoma is to be di ff erentiated from chronic osteomyelitis, osteoclastoma, bone cysts and syphilitic osteitis. In endemic areas the dictum should be ‘any subcutaneous swelling must be considered a m ycetoma until proven otherwise’. Moritz Kaposi , 1837–1902, Hungarian-born Professor of Dermatology viral cause was discovered in 1994. Ernest Codman , 1869–1940, American surgeon. Codman’s triangle can be seen in osteosarcoma, Ewing’s sarcoma, subperiosteal abscess and haematoma. Several imaging techniques are available to confirm the diag - nosis: plain radiography , ultrasonography , CT and magnetic resonance imaging (MRI). Plain radiograph In the early stages, soft-tissue shadows (often multiple) with calcification and obliteration of the fascial planes may be seen. As the disease progresses, the cortex may be compressed from the outside by the granuloma, leading to bone scalloping. Peri - osteal reaction with new bone spicules may create a sun-ray appearance and Codman’s triangle, not unlike an osteogenic sarcoma ( Figure 6.28 ). Late in the disease, ther e may be multi - ple punched-out cavities throughout the bone. Ultrasonography This can di ff erentiate between eumycetoma and actinomy - cetoma as well as between mycetoma and other conditions. In eumycetoma, the grains produce numerous sharp bright hyper-reflective echoes. There are m ultiple thick-walled cavi - ties with absent acoustic enhancement. In actinomycetoma, the findings are similar but the grains are less distinct. The size and e xtent of the lesion can be accurately determined ultrasonically , a finding useful in planning surgical treatment. - - - - - , University of Vienna, Austria, described pigmented sarcoma of the skin in 1872. The

Figure 6.28 Plain radiograph of the knee showing multiple large cavi

ties involving the lower femur, upper tibia and /f_i bula, with well-de /f_i ned margins and periosteal reaction typical of eumycetoma.

(b) Magnetic resonance imaging This helps to assess bone destruction, periosteal reaction and particularly soft-tissue involvement ( Figure 6.29 ) . MRI usually shows multiple 2- to 5-mm lesions of high signal intensity , which indicates the granuloma, interspersed within a low-intensity matrix denoting the fibrous tissue. The ‘dot-in-circle’ sign, which indicates the presence of grains, is highly characteristic. Computed tomography CT findings in mycetoma are not specific but are helpful to detect early bone involvement.

Granuloma Dot-in-circle sign Figure 6.29 (a) Magnetic resonance imaging (MRI) of the foot showing multiple lesions of high signal intensity, which indicates granuloma, interspersed within a low-intensity matrix, which is the /f_i brous tissue and the ‘dot-in-circle’ sign, which indicates the presence of grains. (b) MRI showing massive upper thigh and lower abdominal actinomycetoma.