Endoscopic Ultrasound Diagnosis of Perianal Rhabdomyosarcoma
A 27-year-old male with no significant past medical history, presented to the emergency room with symptoms of perianal pain. Additionally, the patient complained of cramps
in his legs and buttocks for approximately one month. The cramps were initially minor but
progressively worsened and then became constant. His vitals and physical examination were
normal except for his digital rectal examination, which was painful and tender. However, no
obvious mass was felt in the rectum. His initial blood tests were unremarkable which included
hemoglobin-14 g/dl (Nv-13.5-16.5), white cell count-8.9 (Nv-4.5-11), platelets-324 (Nv-150-
400), blood urea nitrogen-12 (Nv-7-25), creatinine 1.2 (Nv-0.4-1.24), sodium-140 (Nv-137-
145) and potassium of 3.7 (Nv-3.5-5.1). Pelvic Computed Tomography (CT) (Figure 1) showed
a mass in the perianal region measuring 12 cm with metastasis to the left iliac and obturator
lymph nodes. In view of the CT findings, other lab tests like Carcinoembryonic antigen (CEA)-
0.5 (Nv-<3 ng/ml), CA 19-9-10 (Nv-<35 u/ml), Human Immunodeficiency Virus (HIV), Human papillomavirus (HPV) and Chlamydia were checked and were all within normal range.
The patient then underwent lower EUS, which showed a 5 cm hypoechoic mass (Figure 2) just
outside the anal canal. An FNA was obtained which showed neoplastic cells (Figure 3A). The
cells were largely mononuclear, with a few binucleate and multinucleate cells. These cells had a
high nuclear cytoplasmic ratio with a relatively round nucleus. Immunohistochemical stain was
positive for muscle (desmin) and more precisely for striated muscle (myogenin, Figure 3B),
supporting the diagnosis of Rhabdomyosarcoma. Subsequent Fluorescent in situ hybridization
(FISH) performed using DNA probe specific for the FOXO1 (FKHR) gene on 13q14 showed
a signal pattern suggestive of rearrangement of FOXO1 gene. Rearrangement of FOXO1 is
associated with a diagnosis of Alveolar Rhabdomyosarcoma.
Gastro Open J. 2015; 1(3): 71-73. doi: 10.17140/GOJ-1-112
