Histopathological parameters of recurrence and malignant transformation in sinonasal inverted papilloma

A combination of parameters may be useful in predicting the clinical course of squamous cell carcinoma in inverted papilloma (IP). In particular, the parameters hyperkeratosis, squamous epithelial hyperplasia and high mitotic index were negative prognostic indicators.

To define histopathological parameters which could predict the recurrence and development of squamous cell carcinoma in IP.

We analyzed the histopathological characteristics of 39 cases of IP using the following parameters: site of origin of tumor; presence of bone invasion; presence of inflammatory polyp; ratio of endophytic to exophytic lesions; ratio of neoplastic epithelium to stroma; presence of hyperkeratosis; presence of squamous epithelial hyperplasia; mitotic index; number of mucin globules; and number of eosinophils.

Malignancy was related to the presence of bone invasion (p=0.039), the absence of inflammatory polyp (p=0.033), increase in the ratio neoplastic epithelium:stroma (p=0.037), increase in hyperkeratosis (p=0.030), the presence of squamous epithelial hyperplasia (p=0.044), increase in the mitotic index (p=0.029) and a decrease in the number of eosinophils (p=0.037). Multiple recurrences (without malignancy) were related to frontal sinus origin (p=0.042), increase in hyperkeratosis (p=0.041), the presence of squamous epithelial hyperplasia (p=0.044) and increase in the mitotic index (p=0.031). Clinically benign behavior was related to the presence of inflammatory polyp (p=0.010) and the absence of hyperkeratosis (p=0.008).