Hormone receptor expression, clinical and histopathological analysis in feline injection site sarcomas.

Feline injection site sarcomas (FISS) are aggressive, with high recurrence and rarely metastasising. The objective of this study was to evaluate, by immunohistochemistry, the expression of oestrogen (ER) and progesterone (PR) receptors in FISS and correlate them with clinical and histopathological aspects. This was a retrospective study with 51 cases of FISS. Immunohistochemistry was performed to detect vimentin, ER, PR and Ki67 expression. Clinical, histopathological and immunohistochemical characteristics were predictor variables and the expression of ER and PR were the dependent ones. Twenty-eight (55%) of the 51 FISS cases were female and 23 (45%) male with 10.7 ± 4.2 years and median tumour size of 3 cm (2.0-5.4). The trunk was the most affected site, with 38 cases (84%). Histological grade III was observed in 57% of the cases, considering differentiation score, necrosis and mitotic index. ER expression, positive in 64% of cases, was associated with the mitotic index (P = .05) and degree of pleomorphism (P = .04). PR was not associated with the variables and 63% of cases were negative for this receptor. Thus, ER expression can affect tumour growth. The knowledge on the FISS hormonal expression is important to clarify the pathophysiological mechanisms. Further studies are needed to predict the value of ER expression in the prognosis of FISS.