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

Abstract

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.

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

“…In FPH cases, multiple lesions developed in the limb, trunk, and/or the head of middle-aged to elderly cats, which is consistent with previous findings. 1,5,34 Regarding feline HS, there have only been a few case reports. 17,33,35,36,46 The present study is the first to describe the clinical and pathological features of feline HS in a series of cases.…”

“…In previous studies on FPH, 3/25, 4/5, and 24/26 cases were immunohistochemically positive for E-cadherin; however, CD204 was not examined. 1,5,34 Moreover, the epitheliotropism of neoplastic cells was reported in some E-cadherin-positive cases. Therefore, LC has been suggested as the origin of FPH.…”

“…Therefore, LC has been suggested as the origin of FPH. 5 In the present study, the E-cadherin expression of FPH was further examined in vitro and in vivo using a novel cell line (AS-FPH01) and its xenotransplant mouse model of FPH. AS-FPH01 was established from an E-cadherin-negative FPH tissue (case 2).…”

Multifocal cutaneous non-epitheliotropic B-cell lymphoma in a cat

“…The differential diagnosis for this pathology may indicate Sézary syndrome, a rare end-stage leukaemic variant of cutaneous T-cell lymphoma and cutaneous lymphoid hyperplasia; 40 , 41 disseminated cutaneous mast-cell tumours; 8 feline skin fragility syndrome; 42 cutaneous lymphosarcoma that could present in association with paraneoplastic syndromes; 37 cutaneous lymphocytosis, a rare benign form characterised by proliferation of T and/or B lymphocytes in the dermis and could be fatal when presenting with visceral involvement; 43 , 44 and, finally, feline progressive histiocytosis. 45 …”

“…4 The differential diagnosis for this pathology may indicate Sézary syndrome, a rare end-stage leukaemic variant of cutaneous T-cell lymphoma and cutaneous lymphoid hyperplasia; 40,41 disseminated cutaneous mastcell tumours; 8 feline skin fragility syndrome; 42 cutaneous lymphosarcoma that could present in association with paraneoplastic syndromes; 37 cutaneous lymphocytosis, a rare benign form characterised by proliferation of T and/ or B lymphocytes in the dermis and could be fatal when presenting with visceral involvement; 43,44 and, finally, feline progressive histiocytosis. 45 Non-epitheliotropic lymphomas affecting the skin are poorly responsive to chemotherapy or radiation therapy. 11 Treatments described for feline cutaneous lymphoma include the use of corticosteroids alone, chemotherapy (CHOP protocol; vincristine and cyclophosphamide), placental lysate, and intravenous and local administration of fibronectin.…”