Incomplete histological margins following planned narrow excision of canine appendicular soft tissue sarcomas and mast cell tumors, using the residual tumor classification scheme

Abstract

Objective To describe the frequency of incomplete histological margins following planned narrow excision (PNE) of mast cell tumors (MCTs) and soft tissue sarcomas (STSs), and to assess the residual tumor classification (R) scheme for reporting histological margins in clinical cases. Study design Retrospective clinical study. Sample population Forty‐four client‐owned dogs with 47 masses. Methods Medical records of dogs undergoing planned narrow excision of STSs and MCTs were reviewed (2016‐2019). Histologic specimens were reviewed by a single pathologist and assigned R scoring (histologically incomplete/R1 margins defined as “tumor on ink”). Results Six out of 23 (26%) MCT PNEs and 10/42 (42%) of STS PNEs resulted in R1 margins. R1 margins were more likely when performing PNE with 6‐10 mm lateral measured surgical margins (LMSMs) versus 0‐5 mm LMSM for MCTs (1/14 vs 5/9), but not STSs (3/7 vs 7/17) (P = .049). The R scheme resulted in higher retrospective percentage agreement in histological reporting than defining incomplete histological margin as tumor cells within ≤1 mm of the margin (83% vs 68% agreement). Complications occurred in 12/47 surgeries, with none requiring additional surgery. Tumors recurred in 3/18 (17%) STSs and 2/18 (11%) MCTs. Conclusion Fewer R1 margins were obtained when PNE with LMSM of 6‐10 mm was performed for mast cell tumors. The use of the R scheme increased agreement in histopathological margin assessment. Clinical significance Planned narrow excision is a viable technique for histopathological diagnosis of appendicular soft tissue sarcomas and mast cell tumors for limb salvage.

Pre‐operative neoadjuvant vinblastine‐prednisolone in canine mast cell tumours: A single‐centre retrospective cohort study

“…This is especially important given the lack of standardised assessment of histological margins, definition of complete margins and minimal recommended histological-free margin in canine MCT. 3,31,55,69 The residual tumour classification scheme 31,70 was considered the most appropriate to use knowing the limitation of this study. Additionally, the MC was analysed both as a continuous and categorical variable with the aim to limit bias due to interpathologist variation.…”

Preliminary Assessment of Tumor-Associated Tissue Eosinophilia (TATE) in Canine Mast Cell Tumors: Prevalence and Prognostic Relevance and Its Association with Neoangiogenesis

“…A total of 87 archived formalin-fixed, paraffin-embedded (FFPE) cases of canine cutaneous MCTs were retrieved from the Tumor Registry of the Department of Veterinary Sciences of the University of Pisa. All samples came from solitary nonulcerated MCTs fully excised with clear margins [25], belonged to dogs without any other treatments (e.g., chemotherapy, radiotherapy), and were submitted for histopathology evaluations from 2009 to 2015. For each case, breed, age, sex, and anatomic location of the tumors were recorded, follow-up data on subsequent local and distant tumor recurrence were collected from referring veterinarians.…”

“…For each MCT, histological grading was assessed according to both the Patnaik et al (1984) [26] and Kiupel et al [27] classifications. Histological safety margins were assessed following the latest guidelines proposed by Haine et al [25], which defined incomplete histological margins as the presence of neoplastic cells within ≤1 mm from the margins. Additionally, TATE was obtained by counting the mean number of eosinophils in 10 consecutive high-power fields (HPF, 2.37 mm 2 ), in the hotspot, avoiding necrotic and hemorrhagic areas.…”