Case 292 -- A Mass in the Right Ischial Rectal Fossa

Contributed by Regina Schmidt, MD, Uma Rao, MD, Sam Yousem, MD.
Published on line in January 2002


This 30-year-old male presents with a four-month history of worsening symptoms of urinary frequency, urgency and hesitancy and change in stool caliber. He also complained of pain radiating to his right hip and thigh. Radiographic studies revealed a 10 x 9.2 x 6.6 cm mass in the right ischial rectal fossa extending through the sciatic notch and encompassing the right sciatic nerve. There is no evidence of metastasis or lymphadenopathy. Based on FNA and core biopsy, the patient received two rounds of chemotherapy prior to excision of the mass.

The FNA showed a spindle cell population with an elevated N:C ratio, nuclear hyperchromasia and moderate pleomorphism. Immunohistochemical staining was positive for vimentin, AE1/3, with patchy weak positivity for actin. Stains were negative for CD34 and CD31.


The specimen consists of an 8.5 x 6.0 x 5.0 cm, 100 gram, rounded portion of moderately firm, red-tan tissue. The cut surface is solid and fleshy with a pale tan-white uniform appearance with areas of focal hemorrhage.



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