[693] Where the Living Meets the Dead: Rinds of Bizarre Stromal Cells with Atypical Mitoses in Pseudosarcomatous Gastrointestinal (GI) Tract Lesions

Oliver G McDonald, Elizabeth A Montgomery. Johns Hopkins Medical Institutions, Baltimore, MD

Background: Pseudosarcomatous stromal lesions with bizarre cells are well-known in GI ulcers and polyps. They are benign, usually showing scant mitotic activity without atypical mitoses. We describe 8 additional cases with features distinct from those previously reported.
Design: Cases were retrieved from file; most (7/8) were consultation cases with an impression or diagnosis of malignancy. Follow-up (FU) was obtained. When possible, lesions were stained with p53 and Ki-67 as were TMA slides from high-grade pleomorphic sarcomas.
Results: Lesions involved the GI tract (7/8, 5 colorectal, 1 ileal) and a suprapubic ulcer. Patient ages ranged from 40-78 (median, 71) years. Available past medical history (4 cases) gave evidence of ischemia (septic shock, vasculitis, angioplasty and thrombosis, anemia), 2 patients had a history of radiation, and 1 had Crohn Disease. Lesions were inflammatory polyps (4), granulation tissue-predominant inflammatory polyps (3), or granulation tissue polyps (1). All cases showed bizarre pleomorphic fibroblasts (A-E), surface ulceration, and mitotic figures. Most (7/8) had atypical mitoses (A). All 8 cases had a thick well-organized, zonal “rind” of bizarre stromal cells between the ulcerated non-viable surface and deep granulation tissue (C-E). This architectural feature was diagnostic of a benign process. Tested pseudosarcomas were strongly, diffusely p53 reactive (B) (2/2, 100%), with low K-i67 indices (5-10%, 4 cases). Control pleomorphic sarcomas (14) had variable p53/Ki-67 patterns. On FU (6 patients; 7-59 months; median 15 months), no lesion recurred or resulted in death of the patient.

Conclusions: Here we present a distinct series of ulcerated lesions with bizarre pseudosarcomatous stromal atypia. These lesions closely mimic sarcomas, including nuclear features that appear overtly malignant, mitotic activity, and atypical mitoses. Immunohistochemical staining for p53 and Ki-67 does not appear to discriminate these benign lesions from sarcomas. The diagnosis is made by low-power examination of H&E sections; a zonal “rind” of bizarre stromal cells can be seen within the (presumably) hypoxic zone located between granulation tissue and the ulcerated surface, i.e. “where the living meets the dead”.
Category: Gastrointestinal

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 120, Tuesday Afternoon


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