Epidemiology and Survival of Dogs Diagnosed with Splenic Lymphoid Hyperplasia, Complex Hyperplasia, Stromal Sarcoma and Histiocytic Sarcoma

Abstract

Canine splenic fibrohistiocytic nodules traditionally encompassed benign lymphoid hyperplasia, complex hyperplasia, and malignant fibrous histiocytoma. The latter has been recently re-classified into histiocytic sarcoma and stromal sarcoma. Reliable indicators of post-splenectomy survival and demographic factors predisposing to the four types of nodules are not completely understood. This study aims to estimate frequency, survival times, and identify risk factors of splenectomized dogs diagnosed with lymphoid hyperplasia, complex hyperplasia, histiocytic sarcoma, and stromal sarcoma using medical records containing histopathological diagnosis from the VetCompass Australia database (1989–2018), which collects demographic, and clinical information from veterinary clinics. Out of 693 dogs, 315 were diagnosed with fibrohistiocytic nodules, mostly lymphoid hyperplasia (169/693, 24.4%), followed by stromal sarcoma (59/693, 8.5%), complex hyperplasia (55/693, 7.9%), and histiocytic sarcoma (32/693, 4.6%). Dogs aged 8–10 years were more likely to be diagnosed with histiocytic or stromal sarcoma than lymphoid hyperplasia. Dogs diagnosed with lymphoid hyperplasia had a longer survival time than those with other diagnoses (median > 2 years). Dogs diagnosed with histiocytic sarcoma had longer survival times (median 349 days) than stromal sarcoma (median 166 days). Results suggest that knowledge of the type of splenic fibrohistiocytic nodule, patients’ age, and sex can be used to increase prognostic accuracy.

Splenic stromal sarcomas in dogs: Outcome and clinicopathological prognostic factors in 32 cases

“…The findings of this study align with the existing literature, which indicates that SSS are relatively rare in dogs. [12][13][14] Over a period of 13 years, this study collected only 32 cases from multiple institutions, highlighting the uncommon nature of this tumour in the canine population.…”

“…1,[5][6][7][8] The limited availability of clinical information and the wide range of median survival times, spanning from 60 to 599 days, can be attributed to the relatively low frequency of splenic sarcomas in dogs, the lack of comprehensive medical records, and the inclusion of heterogeneous entities in most studies. 6,[8][9][10][11][12][13][14] Noteworthy, histiocytic sarcomas were originally included along with SNANLSTSs, but are currently considered as a different entity due to their myeloid (non-stromal) origin and their specific behaviour and treatment. 7,[13][14][15] With regard to their embryologic origin, tumours arising from the splenic stroma are now classified under the term 'Splenic Stromal Sarcomas' (SSS), replacing the previous term of SNANLSTSs.…”

“…6,[8][9][10][11][12][13][14] Noteworthy, histiocytic sarcomas were originally included along with SNANLSTSs, but are currently considered as a different entity due to their myeloid (non-stromal) origin and their specific behaviour and treatment. 7,[13][14][15] With regard to their embryologic origin, tumours arising from the splenic stroma are now classified under the term 'Splenic Stromal Sarcomas' (SSS), replacing the previous term of SNANLSTSs. 11,15 This classification includes various histotypes such as fibrosarcoma, myxosarcoma, leiomyosarcoma, liposarcoma, and undifferentiated stromal sarcoma (whether arising from complex nodular hyperplasia (CNH) or not).…”

“…This approach is expected to enhance our understanding of their biology, improve clinical management, and address the challenges associated with comparing different study results. 7,13,14 Considering the low frequency observed in daily clinical practice, the limited number of cases described in the literature, and the evolving diagnostic techniques and terminology in recent years, only little information is available on prognostic factors. Mitotic count has been identified as the variable most strongly associated with the biological behaviour of SSS.…”

Clinicopathologic features and biologic behavior of canine splenic nodules with stromal, histiocytic and lymphoid components

“…Additionally, the median survival time of dogs that died of disease-related causes (234 days with no adjuvant medical treatment) is quite divergent from the survival times usually reported for canine HS, a highly aggressive disease requiring specific chemotherapeutic treatment. Recently, a localized form of splenic HS with longer survival (median, 349-427 days) has been reported; possibly the inclusion of these mixed lesions might have contributed to increase the survival times of dogs in those studies (7,8).…”