Canine melanoma diagnosis: RACK1 as a potential biological marker

Area of Science:

• Veterinary Pathology
• Canine Oncology
• Molecular Diagnostics

Background:

• Canine melanoma diagnosis is complex due to varied histological presentations.
• Identifying reliable malignancy markers is crucial for accurate classification.
• Receptor for activated C-kinase 1 (RACK1) has shown potential in characterizing melanomas in other species.

Purpose of the Study:

• To evaluate the utility of RACK1 detection for classifying canine melanocytic neoplasms.
• To differentiate between benign melanocytomas and malignant melanomas in dogs.
• To correlate RACK1 expression patterns with tumor morphology and malignancy indicators.

Main Methods:

• Immunofluorescence and immunohistochemistry were used to detect RACK1 and microphthalmia-associated transcription factor (MITF) in canine skin and tumor samples.
• Tumors were classified as melanocytomas or melanomas based on morphology, mitotic index, and Ki-67.
• RACK1 staining patterns (homogeneous vs. heterogeneous) were analyzed and correlated with malignancy features.

Main Results:

• MITF was confirmed as a marker for canine melanocytic cells (100% positivity).
• RACK1 was detected in all melanocytic lesions (100%) but not in healthy skin.
• Homogeneous RACK1 cytoplasmic staining was characteristic of melanomas (13/13), while heterogeneous staining indicated melanocytomas (11/11).
• RACK1 labeling correlated with increased cell and nuclear size, indicators of malignancy.

Conclusions:

• RACK1 serves as a potential diagnostic marker for distinguishing canine melanomas from melanocytomas.
• Fluorescent RACK1-MITF labeling offers a reliable method for classifying these tumors, especially in pigmented samples.
• RACK1 expression patterns provide valuable insights into the malignancy of canine melanocytic neoplasms.