Ocular histiocytic sarcoma in a cat

A Scoping Review on Tyrosine Kinase Inhibitors in Cats: Current Evidence and Future Directions

Tyrosine kinase inhibitors (TKIs) have become invaluable in the treatment of human and canine malignancies, but their role in feline oncology is less defined. While toceranib phosphate and masitinib mesylate are licensed for use in dogs, no TKI is yet approved for cats. This review systematically maps the research conducted on the expression of tyrosine kinases in neoplastic and non-neoplastic domestic feline tissues, as well as the in vitro/in vivo use of TKIs in domestic cats. We identify and discuss knowledge gaps and speculate on the further research and potential indications for TKI use in cats. A comprehensive search of three electronic databases and relevant paper reference lists identified 139 studies meeting the inclusion criteria. The most commonly identified tumors were mast cell tumors (MCTs), mammary and squamous cell carcinomas and injection-site sarcomas. Based on the current literature, toceranib phosphate appears to be the most efficacious TKI in cats, especially against MCTs. Exploring the clinical use of TKIs in mammary carcinomas holds promise. Despite the progress, currently, the evidence falls short, underscoring the need for further research to discover new indications in feline oncology and to bridge the knowledge gaps between human and feline medicine.

Bilateral renal histiocytic sarcoma with disseminated lung involvement in a Siberian Forest Cat

Case summary

A 5-year-old female neutered Siberian Forest Cat presented with a 7-day history of lethargy, hyporexia and weight loss. Abdominal ultrasonography revealed bilateral renal changes suggestive of neoplasia. Thoracic radiography documented diffuse pulmonary nodules. The cat was euthanased during diagnostic investigations. Histopathological assessment and immunohistochemical staining of post-mortem renal biopsies were consistent with a histiocytic lesion, most likely histiocytic sarcoma (HS). The lung lesions were suspected of representing disseminated disease.

Relevance and novel information

HS is considered a rare neoplastic process in cats. This report describes a case of feline bilateral renal HS with suspected concomitant pulmonary involvement. A primary renal origin was suspected, with the lung lesions being a result of disseminated disease. Renal HS should be included as a differential diagnosis when renal ultrasonography reveals changes suggestive of neoplasia.

Oral histiocytic sarcoma in a cat with mandibular invasion and regional lymph node metastasis

Case summary

An 11-year-old female spayed domestic medium-hair cat presented for dental prophylaxis, at which time no oral mass was appreciated. Fifteen days after a dental cleaning, a mass expanding the oral mucosa of the rostral mandible was identified. An incisional biopsy revealed that the oral mucosa was infiltrated by neoplastic round-to-spindloid mesenchymal cells arranged in streams and small, dense aggregates consistent with an undifferentiated sarcoma. The patient was managed medically for approximately 6 months following the diagnosis, but, owing to declining health, euthanasia was elected and a post-mortem examination was performed. On post-mortem examination, the previously described neoplastic cells were infiltrating the rostral mandible and had metastasized to the right submandibular lymph node. Immunohistochemistry performed during the postmortem examination found that neoplastic cells were positive for Iba-1, CD18 and CD204, and negative for MUM-1, S100, Melan-A and E-cadherin, favoring a diagnosis of oral histiocytic sarcoma. Although recently recognized in cats, feline oral histiocytic sarcoma is rare, the tumor’s immunohistochemical profile is unstandardized, and the tumor’s behavior and prognosis are unclear. The diagnosis is challenging if small incisional biopsies are submitted and the neoplasm is poorly differentiated. This case report discusses the clinical, macroscopic, microscopic and immunohistochemical features of oral histiocytic sarcoma in a cat with mandibular invasion and submandibular lymph node metastasis.

Relevance and novel information

Feline primary oral histiocytic sarcoma is rare and tumor behavior and prognosis are unclear. This report broadens the immunohistochemical features of the tumor and recognizes mandibular invasion and submandibular lymph node metastasis.

Periarticular histiocytic sarcoma with heart metastasis in a cat

A 4-year-old intact female domestic short-haired cat was referred for recommendations about adjuvant medical treatment 1 month after left forelimb amputation due to periarticular histiocytic sarcoma (HS). At presentation, physical abnormalities were limited to enlarged ipsilateral superficial cervical and axillary lymph nodes. Routine blood analysis, abdominal ultrasound, and thoracic radiology were unremarkable. The cat initially received lomustine without any adverse events. Four weeks later, the cat developed severe acute respiratory distress. Results of thoracic radiographs and transthoracic echocardiographic analysis were suggestive of pulmonary and heart metastasis. Due to the cat's poor clinical condition and prognosis, the owner elected euthanasia, and a necropsy was performed. Based on gross pathology, histopathology, and immunohistochemistry, an HS with nodal, renal, pulmonary, and heart (right auricular and right ventricular) metastases was diagnosed. This case represents the first description of HS with a heart metastasis in a cat, providing further insight into the clinical course and metastatic behavior of this rare malignant neoplasm. Clinicians should be aware of this site of metastasis and consider HS in the list of differential diagnoses for secondary heart tumors in cats.

Primary histiocytic sarcoma in the brain with renal metastasis causing internal ophthalmoparesis and external ophthalmoplegia in a Maine Coon cat

Case summary

An 11-year-old neutered male Maine Coon cat was presented for investigation of anisocoria and depression. Neurological examination was consistent with a lesion at the level of the middle cranial fossa, and biochemistry was indicative of moderate renal functional impairment. MRI of the brain identified an extra-axial mass lesion at the level of the middle cranial fossa, T2-weighted hyperintense and strongly homogeneously contrast enhancing with dural tail. The cat was euthanased after 6 weeks of palliative treatment with corticosteroids. Histopathology and immunohistochemistry of the brain, the intra-cranial mass and the renal masses found on necropsy were consistent with histiocytic sarcoma.

Relevance and novel information

Central nervous system histiocytic sarcoma is a rare finding in cats. This original case report describes the neurological presentation, novel MRI characteristics and pathological findings of suspected primary histiocytic sarcoma affecting the brain with renal metastasis in a cat.

Oral histiocytic sarcoma in a cat

Case summary

A 15-year-old neutered male domestic shorthair cat presented with a 4-week history of dysphonia and reluctance to chew hard food. Oral examination revealed a mass lesion on the caudal soft palate. Biopsy was performed and histopathology with immunohistochemistry was most consistent with histiocytic sarcoma. CT of the head identified a discrete, left-sided, soft tissue mass lesion cranial to the tonsil with bilaterally symmetrical regional lymph nodes. CT of the thorax was unremarkable. Surgical removal achieved cytoreduction but not complete removal. Adjuvant chemotherapy with lomustine 10 mg (30 mg/m²) was initiated. The patient developed suspected pancreatitis 2–3 weeks postoperatively, so further chemotherapy treatment was discontinued, but supportive treatment with pain relief and appetite stimulants was provided. Three months postoperatively, the patient developed recurrent dysphonia, and oral examination revealed a suspicion of local recurrence. Confirmation of diagnosis (cytopathology or histopathology) was not obtained. Supportive treatment to maintain a good quality of life was continued and the patient was euthanased 6 months after diagnosis owing to progressive disease.

Relevance and novel information

Only a few reports have been published describing histiocytic diseases of cats. To our knowledge, this is the first report of a feline histiocytic sarcoma of the oral cavity. Therefore, histiocytic sarcoma should be considered as a differential diagnosis in feline patients with an oral mass, especially if histopathology suggests a pleomorphic and poorly differentiated sarcoma. Immunohistochemistry for the confirmation of cell line origin would be strongly recommended.

Immunophenotyping of Nonneoplastic and Neoplastic Histiocytes in Cats and Characterization of a Novel Cell Line Derived From Feline Progressive Histiocytosis

Histiocytic proliferative diseases are rare in cats, and their pathogenesis is poorly understood. In the present study, 25 cases of histiocytic sarcoma (HS) and 6 of feline progressive histiocytosis (FPH) were examined, and survival times were recorded in 19 cases. The immunophenotypes of tumor cells in these cases as well as of nonneoplastic feline histiocytes were characterized using formalin-fixed, paraffin-embedded tissues. An FPH cell line (AS-FPH01) and xenotransplant mouse model of FPH were also established. The median survival time of HS (150 days) was significantly shorter than that of FPH (470 days). Immunohistochemically, nonneoplastic histiocytes were immunopositive for various combinations of Iba-1, HLA-DR, E-cadherin, CD204, CD163, CD208, and MAC387. By immunohistochemistry, dermal interstitial dendritic cells (iDCs) and macrophages were CD204+/E-cadherin-, while epidermal Langerhans cells (LCs) were CD204-/E-cadherin+. Neoplastic cells of 4 FPH and 18 HS were CD204+/E-cadherin- (iDC/macrophage immunophenotype), while 2 FPH and 2 HS were CD204-/E-cadherin+ (LC immunophenotype), and 5 HS were CD204+/E-cadherin+ (LC-like cell immunophenotype). Furthermore, immunohistochemical and western blot analyses of AS-FPH01 cells derived from E-cadherin-negative FPH revealed that cultured cells were immunopositive for both CD204 and E-cadherin in vitro and in vivo. These results indicate that the neoplastic cells of feline HS and FPH were variably positive for iDC/macrophage and LC markers, and their immunophenotype changed in different microenvironments. The novel cell line established in the present study may serve as an experimental model of FPH that will enable further molecular and therapeutic studies on this disease.

Ophthalmopathologic characterization of multicentric or metastatic neoplasms with an extraocular origin in dogs and cats

OBJECTIVE

To characterize the frequency and distribution of secondary ocular neoplasms in dogs and cats identified during necropsy.

METHODS

A retrospective analysis of necropsy records of dogs and cats was conducted, and cases with metastatic/multicentric neoplasms with an extraocular origin, involving the eyes, were selected.

RESULTS

From January 2015 to January 2019, we identified a total of 233 dogs and 100 cats with metastatic disease. Of these, 11.6% (27/233) of the dogs and 13% (13/100) of the cats had ocular metastases. Lymphoma was the most common multicentric neoplasm involving the eyes of both species. In dogs, these neoplasms occurred bilaterally, predominantly in the anterior uvea, and were diffuse large B-cell, T-lymphoblastic, peripheral T-cell not otherwise specified, and lymphocytic B-cell lymphomas. In cats, feline leukemia virus (FeLV)-associated T-cell lymphoma was the most common. Mammary carcinoma was the second most common ocular metastatic neoplasm in bitches, with a predominantly unilateral involvement of the uveal tract. In cats, following lymphoma, pulmonary and squamous cell carcinomas were the most common multicentric/metastatic neoplasms of the eyes. Individual cases of cholangiocarcinoma, hemangiosarcoma, and chemodectoma in dogs, as well as mammary gland cribriform carcinoma, salivary gland carcinoma, and histiocytic sarcoma in cats were detected.

CONCLUSIONS

The eyes of dogs were mostly affected by lymphoma or mammary gland carcinoma, while those of cats mostly had lymphoma, pulmonary carcinoma, or squamous cell carcinoma as the main metastatic/multicentric neoplasm. To the best of our knowledge, this is the first study to identify intraocular metastatic cholangiocarcinoma and chemodectoma in dogs, aside from identifying salivary gland carcinoma in cats.

Feline progressive histiocytosis: a retrospective investigation of 26 cases and preliminary study of Ki67 as a prognostic marker

Feline progressive histiocytosis (FPH) is an uncommon and infrequently reported cutaneous histiocytic proliferative disorder, whose clinical presentation is solitary or multiple cutaneous nodules and papules, with late-course internal metastasis. We describe herein the clinical, epidemiologic, histologic, and immunohistochemical features of this entity, and document the outcome of FPH based on a retrospective study of 26 cases. Female and male cats were affected equally. Lesions were evident either as solitary (16 of 26 cases) or multiple (10 of 26 cases) nonpruritic and alopecic nodules or plaques, preferentially located on the legs and extremities (73%). Follow-up was complete for 19 cats, and ranged from 41 to 1,449 d. Nine died of FPH with a median overall survival of 96 d (range: 41-238 d). The disease recurred in 14 cats after surgical excision of the nodules, and the median disease-free survival was 175 d (range: 21-1,449 d). Five of the 26 cats were alive at the end of the study, and 4 had no progression of the disease. Histologically, lesions were characterized by poorly circumscribed, unencapsulated histiocytic infiltration of dermis and subcutis. Epitheliotropism was observed in 11 (42%) cats. Atypical histiocytes diffusely and consistently expressed MHC II, CD18, and Iba1. Statistically significant higher E-cadherin expression was observed in epitheliotropic cases compared to non-epitheliotropic cases. A negative correlation between overall survival and proliferation index was evident, thus suggesting Ki67 as a promising prognostic marker.

Establishment and characterization of a cell line from a feline histiocytic sarcoma

Feline histiocytic sarcoma (HS) is an aggressive and uncommon tumor originating from dendritic cells/macrophages. Here, a feline HS cell line, FHS-1, was established from a case of feline HS and characterized. Immunohistochemically, FHS-1 cells were positive for vimentin and Iba-1, and negative for MHC class II and CD163. FHS-1 cells were positive for α-naphthyl butyrate esterase staining, which was clearly inhibited by sodium fluoride. FHS-1 cells had phagocytic and antigen uptake/processing activities. Moreover, FHS-1 cells were tested for susceptibility to feline infectious peritonitis virus (FIPV) strain 79-1146; however, this cell line was not susceptible to this viral strain. Although FHS-1 cells lost the expression of MHC class II and CD163, our findings indicate that FHS-1 is a feline HS cell line that retains functional properties of dendritic cells/macrophages in terms of phagocytic and antigen uptake/processing activities. While FHS-1 cells are not suitable for in vitro study of FIP using strain 79-1146, they may be applicable for studies aimed at developing new diagnostic and therapeutic strategies for feline HS.

Clinical outcome, PDGFRβ and KIT expression in feline histiocytic disorders: a multicentre study

Information about histiocytic disease in cats is limited. The aim of this study was to document clinical findings and outcome in feline histiocytic disorders, and characterize the expression of PDGFRβ and KIT in order to identify potential treatment targets. Morphologically diagnosed feline histiocytic tumours were reviewed and characterized by immunohistochemistry (IHC). Five cases of feline progressive histiocytosis (FPH), eight histiocytic sarcomas (HS) and two haemophagocytic histiocytic sarcomas (HaeHS) were confirmed. PDGFRβ was variably positive in most histiocytic cases, while KIT was negative in all. Clinical presentation, treatment and outcome were also evaluated. Partial responses were recorded in measurable disease with tyrosine kinase inhibitors and lomustine, and radiotherapy achieved long-term control in some cases. Survival times were shortest in HaeHS and disseminated disease. PDGFRβ, but not KIT, may represent a therapeutic target in feline histiocytic disorders but more studies are needed to investigate other potential treatment targets.