Contributed by Jason Chiang, MD, PhD and Sarangarajan Ranganathan, MD
The patient was 7-month-old male with a 4.5 cm deep left inner thigh lesion for four months. The lesion was initially swollen, tender and erythematous. It gradually improved, changed to a darker color, and then stabilized. No fluctuance or drainage was noted. The area showed deep induration and was not warm to touch. Range of motion was somewhat limited. He had some fevers during the past few months and was treated with multiple antibiotics. X-rays were taken by the PCP and were negative.
He was well nourished and developed with no acute distress and no fever at presentation. Physical examination was otherwise normal, with normal muscle bulk and no obvious deformities. No abdominal masses or hepatosplenomegaly was noted. Family history was non-contributory. Laboratory studies showed hematocrit 31.8% (normal 33 - 39%), 11% monocytes (normal 3 - 9%), 6% eosinophils (normal 0 - 3%), platelet count 249,000/ul (normal 156,000 - 369,000/ul), and normal PT/PTT. Fibrinogen level was 308 mg/dL (normal 205 - 508 mg/dL) and D-dimer was 2.13 ug/mL (normal < 0.5 ug/mL). He was initially referred to Dermatology with the impression of a resolved abscess or infection with post-inflammatory changes. Imaging studies were scheduled for possible deep lesions.
RADIOLOGIC AND IMAGING FINDINGS
Ultrasound studies showed an irregular, infiltrating, ill-defined and hypoechoic area between muscle bundles. Color and pulse Doppler evaluation showed markedly increased blood flow throughout the area. Classic ultrasound findings of a hemangioma, which is usually sharply demarcated and not infiltrating, were not present.
MRI showed an ill-defined lesion with bright T2 signal, infiltrative borders and focal areas consistent with adipose tissue (Figs. 1 and 2). The lesion located in the intermuscular plane and extended into subcutaneous tissue.
MR angiography showed increased number of vessels with a branching pattern. Draining vessels is present inferior to the lesion (Fig. 3).
Tissue diagnosis was recommended to ascertain the nature of the lesion. Biopsy was performed.
The specimen consists of three cores of pink-tan and soft tissue, measuring 0.6 - 1.9 cm and 0.1 cm in diameter.
Histologic sections show a cellular spindle cell lesion with indistinct borders and a somewhat diffuse, infiltrative growth pattern in a fibrous stroma. The lesional cells form interconnecting vascular channels. Fibrin/platelet thrombi can be seen in some channels. The cells show a moderate amount of eosinophilic cytoplasm, indistinct cell borders, somewhat pleomorphic nuclei and indistinct nucleoli. No atypical mitosis or necrosis is present (Figs. 4, 5, 6, 7, and 8).
Some neoplastic cells are positive for D2-40 (Fig. 9). Tumor cells are negative for GLUT-1 (Fig. 10). Ki-67 proliferation index is variable, focally up to 15-20% and in average 8-10%. Controls are appropriate.