PMC8592917_01
The swelling near the right wrist with the inability to move the right little and ring figures are shown. The abdominal distension (massive hepatosplenomegaly), the BCG site and a subcutaneous nodule are also evident.
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F1
At 31/2 months of age, he developed a tender swelling in the right lower forearm (Figure 1). The skin examination was remarkable for a prominent BCG scar (Figure 1), and skin-colored soft nodules such as the one in the lateral chest cage (Figure 1).
Radiographic images taken at about 31/2 months of age. (A): Radiograph of the right forearm showing abnormal texture in the distal ulnar, with areas of bone destruction and resorption surrounded by soft tissue swelling. (B,C): MRI of the right forearm (with and without contrast) showing destructive bone lesion involving the ulnar with a large, enhancing soft tissue mass extending into the interosseous space, measuring 2.5 x 2.5 x 4.5 cm. The mass involves the diaphysis and distal metaphysis. There is periosteal reaction and edema in the surrounding soft tissue and subcutaneous fat. There is also abnormal signal and enhancement of the distal ulnar growth plate with displacement. (D,E): Chest radiograph and chest CT scan showing nodular lesions in both lungs. (F,G): Abdominal CT scan and ultrasound showing the right hepatic lobe exceeding the costal margin, measuring 8.6 cm craniocaudally. The spleen measures 7.0 cm in length and shows two focal hypodense lesions, the largest measuring 1.01 x 0.86 cm (arrowed).
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F2
Radiograph and magnetic resonance imaging (MRI) of the right forearm showed areas of bone destruction (resorption) in the distal ulnar, surrounded by a soft tissue mass (Figure 2). Chest radiograph and chest CT showed nodular lesions in the lungs (Figure 2). Ultrasound and computed tomography (CT) scan of the abdomen showed organomegaly with two focal hypodense splenic lesions (Figure 2).
Sections of routine stain from the soft tissue mass right distal ulna. (A) shows sheet of mononuclear cells of lymphocytes and histiocytes. (B) shows predominate lymphocytic infiltrate bone and skeletal muscle. (C) shows higher magnification of the right ulnar lesion routine stain section shows mononuclear cells predominantly of lymphocytes with scattered mitosis infiltrating skeletal muscle (skeletal muscle appears as eosinophilic striated tissue with peripheral nuclei at left side of the image). Most of the lymphocytes are B cell with CD20 positive immunohistochemical stain (D), mixed with few scattered T lymphocytes highlighted with CD3 immunohistochemical stain (E). Skin biopsy shows dermal inflammatory cells infiltrate, mainly of histiocytes with granulomatous inflammation (F).
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F3
Morphologically, the specimens showed infiltrating lymphohistiocytic proliferations by small-to-medium size mature/activated B cells [PD1 (programmed cell death protein 1) positive] of non-germinal center origin intermixed with normal histiocytes (Figures 3A-E).