High rates of histopathologic discordance in sarcoma with implications for clinical care.

Abstract

10065 Background: Histology-specific therapy for sarcoma patients (pts) at dedicated sarcoma centers is routinely guided by re-review of histopathology (HP) from referring institutions. We evaluated the rate of discordance between HP diagnoses rendered by the referring institution and our institution and the impact on treatment. Methods: This retrospective study included all pts with a new diagnosis of primary/metastatic sarcoma with available HP slides and reports referred to our sarcoma center January-December 2010. Rates of discordance and impact on treatment and prognosis were assessed. Univariate analyses were performed to evaluate the association of discordance with HP characteristics. Results: Of 795 unique pts referred to our sarcoma center, 335 (42%) met inclusion criteria; ineligible pts included 195 (25%) with recurrence, 92 (12%) without a biopsy, and 36 (5%) from our institution. HP discordance was noted in 79 cases (24%), of which 52 (16%) were deemed clinically significant, altering treatment recommendations (systemic therapy regimen, extent of surgery, use of radiation) and/or prognosis. Using the referring institution’s HP diagnosis as the reference, low discordance rates were noted for GIST (2/49, 4%), angiosarcoma (0/25, 0%), and Ewing sarcoma (1/9, 11%). In contrast, discordance rates were higher for liposarcoma (all subtypes, 5/23, 22%), leiomyosarcoma (7/34, 21%), and rhabdomyosarcoma (5/6, 83%). Ten cases (13%) were diagnosed as “sarcomas” at referring institutions and as non-sarcoma lesions (e.g., lymphoma, melanoma, T11 fracture callus) at our institution. HP materials on 102 pts (30%) were sent for second opinion review prior to referral to our center; 2 cases were discordant. On univariate analysis, referring institution diagnoses of fibroblastic tumors (p=0.04) or tumors with skeletal muscle differentiation (p<0.0001) were significantly more likely to be discordant. Conclusions: Rates of HP discordance in sarcoma can be high and may impact therapeutic decisions in a substantial subset of pts. This may in part reflect the bias of challenging cases referred to a sarcoma center. Nonetheless, pts with the more frequently discordant sarcoma subtypes may benefit from second opinion review.