Agreement Between Cytology and Histopathology for Regional Lymph Node Metastasis in Dogs With Melanocytic Neoplasms

Abstract

Melanocytic neoplasms are common in dogs and frequently occur within the oral cavity or in haired skin. The behavior of melanocytic neoplasms is variable and depends on tumor location, size, and histopathologic features. This study compared cytopathology and histopathology of 32 lymph nodes from 27 dogs diagnosed with melanocytic neoplasms. Agreement between the original cytology report, cytology slide review, original histopathology report, and histopathology slide review was determined for each lymph node. A subset of lymph nodes was subjected to immunohistochemistry (Melan-A) and additional histochemical stains/techniques (Prussian blue, bleach) to assist in differentiation of melanocytes and melanophages. Agreement ranged from slight to fair for each of the variables evaluated with weighted kappa (κ) or kappa (κ) analysis (original cytology vs cytology review κ = 0.24; original cytology vs original histopathology κ = 0.007; original cytology vs histopathology review κ = 0.23; cytology review vs original histopathology κ = 0.008; cytology review vs histopathology review κ = 0.006; and original histopathology vs histopathology review κ = 0.18). The diagnoses (metastatic, equivocal, or negative for metastasis) of the original report and slide review for both cytology and histopathology were not significantly correlated with survival in this population of patients. Overall, agreement between cytology and histopathology was poor even with a single clinical or anatomic pathologist performing slide review. Consensus between routine cytology and histopathology for staging of lymph nodes in patients with melanocytic neoplasms is poor and does not correlate with survival.

A combination of electrochemotherapy, gene electrotransfer of plasmid encoding canine IL-12 and cytoreductive surgery in the treatment of canine oral malignant melanoma

“…The second limitation is that fine-needle aspiration biopsies were not performed in all of the patients but rather just in those with enlarged lymph nodes, while it has been described that lymph node size is not always a predictive factor for metastasis (Williams and Packer, 2003). However, the correlation between cytology and histopathology for staging of lymph nodes in dogs with oral melanocytic neoplasms was recently found to be poor (Grimes et al, 2017). The third limitation is the unavailability of advanced diagnostic techniques (i.e., CT, MRI scanning, etc.)…”

Investigation of the utility of lymph node fine‐needle aspiration cytology for the staging of malignant solid tumors in dogs

“…Although this topic has not been as clearly researched in canine oncology, routine histopathologic examination alone is likely to be a suboptimal gold standard for canine melanoma nodal metastasis assessment. This was highlighted in a recent study, in which the diagnosis of LN melanoma metastasis was changed in 46.9% of dogs after a second opinion was reviewed . This might also explain, in part, why several studies failed to find the prognostic value of using LN FNAC to identify metastatic disease in dogs, while LN metastatic status is of important prognostic value in human melanoma .…”

“…This was highlighted in a recent study, in which the diagnosis of LN melanoma metastasis was changed in 46.9% of dogs after a second opinion was reviewed. 33 This might also explain, in part, why several studies failed to find the prognostic value of using LN FNAC to identify metastatic disease in dogs, 29,34,35 while LN metastatic status is of important prognostic value in human melanoma. 36 The robustness of assessment of the diagnostic utility of FNAC for the detection of melanoma nodal metastases would be enhanced by an optimal gold standard, based on the results of a future comparison of histopathology, IHC, PCR, and combinations thereof, and incorporating follow-up visits.…”

Identification of occult micrometastases and isolated tumour cells within regional lymph nodes of previously diagnosed non‐metastatic (stage 0) canine carcinomas

“…Given the growing awareness of the prognostic and therapeutic implications of micrometastases and ITC, surgical removal of normal‐sized draining lymph nodes for histologic staging is being recommended with increasing frequency . Studies assessing the presence and prognostication of micrometastases, ITC and occult metastases within sentinel and regional lymph nodes of the canine population are lacking, although adoption of this methodology has begun to surface, predominantly within mammary carcinomas, as well as canine mast cell tumours .…”