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Published on: March 29, 2020
Cytologic and immunocytochemical characterization of feline progressive histiocytosis
Nazaré Pinto da Cunha1, Gabriele Ghisleni, Fabia Scarampella
1Department of Veterinary Sciences and Public Health, University of Milan, Milan, Italy.
Insights
Feline Progressive Histiocytosis (FPH) is a skin cancer in cats. Diagnosis is improved by combining cytology and immunocytochemistry, specifically using CD1 markers to identify dendritic cell origin.
Area of Science:
- Veterinary Pathology
- Dermatology
- Cytopathology
Background:
- Feline Progressive Histiocytosis (FPH) is a rare cutaneous dendritic cell neoplasm.
- FPH is often misdiagnosed as inflammatory conditions.
- Cytologic diagnostic criteria for FPH are not well-established.
Purpose of the Study:
- To define the cytologic features of FPH.
- To evaluate immunocytochemical markers for diagnosing FPH.
- To improve the diagnostic accuracy of FPH.
Main Methods:
- Fine-needle aspiration cytology from 5 FPH cases.
- Immunocytochemistry for CD1a, CD1c, CD3, CD11b, CD18, CD21, MHCII.
- E-cadherin assessment and transmission electron microscopy (TEM) in select cases.
Main Results:
- Cytology showed large, round to polygonal cells with abundant cytoplasm and atypical nuclei.
- Neoplastic cells expressed CD1a, CD1c, CD11b, CD18, and MHCII.
- Reactive T cells (CD3+) and variable E-cadherin expression were noted.
Conclusions:
- FPH is a distinct neoplastic lesion of nonphagocytizing histiocytes.
- Immunocytochemistry for CD1 is crucial for confirming dendritic cell origin.
- Combined cytomorphology and immunocytochemistry enable rapid, specific FPH diagnosis.
Background:
Feline Progressive Histiocytosis (FPH) is a cutaneous dendritic cell neoplasm characterized by slow progression and spread to internal organs in the terminal stage. FPH is often misdiagnosed as an inflammatory reaction and has not been fully characterized from a cytologic diagnostic perspective.
Objectives:
The purpose of the study was to characterize the cytologic and immunocytochemical aspects useful for FPH diagnosis.
Methods:
Fine-needle aspiration cytologic samples of 5 cases of FPH confirmed by skin biopsy and necropsy were evaluated. Immunocytochemistry with antibodies recognizing CD1a, CD1c, CD3, CD11b, CD18, CD21, and MHCII was performed on air-dried, acetone-fixed smears. E-cadherin expression was assessed on paraffin-embedded skin biopsies. Transmission electron microscopy (TEM) was performed in one case.
Results:
Main cytologic findings on variably cellular samples were characterized by single to cohesive large, round to polygonal cells with intermediate to low N/C ratio, abundant clear homogeneous cytoplasm, and round to oval nuclei with rare bi- to multinucleated atypical cells, associated with low numbers of small lymphocytes and/or neutrophils. Neoplastic cells expressed CD1a, CD1c, CD11b, CD18, and MHCII. Anti-CD3 antibodies identified reactive T cells admixed with the neoplastic cells. E-cadherin expression was observed in all but one case. TEM failed to identify Birbeck granules in one case.
Conclusions:
FPH is a distinctive neoplastic lesion composed of nonphagocytizing histiocytes variably admixed with neutrophils and small mature lymphocytes. Immunocytochemical analysis with CD1 is mandatory to confirm a dendritic cell origin. Immunocytochemistry and cytomorphology allowed the specific and rapid diagnosis of FPH on cytologic samples.
