Inverted Papilloma of the Ureter with Malignant Transformation: A Case Report and Review of the Literature

Abstract

Inverted papilloma of the ureter is a rare tumor generally considered to be a benign lesion. We present a case of ureteral inverted papilloma with malignant transformation and review the literature. Ten cases of ureteral inverted papillary tumors in Japan and 13 cases of inverted papillary tumors associated with malignancy in the urinary tract in the world literature have been analyzed to define their features. Inverted papillary tumors of the ureter have distinct clinicopathological features, but most are discovered retrospectively after nephroureterectomy. From the standpoint of clinicopathological features, inverted papillary tumor of the ureter should be distinguished from its exophytic counterpart with respect to the treatment. If the tumor can be diagnosed macro- and microscopically during surgery as inverted papilloma or malignant inverted papillary tumor without invasion, partial ureterectomy including the lesion may be recommended. Furthermore, we propose the hypothesis that inverted papillary tumor could be a neoplasm of basal cell origin in the transitional epithelium, termed ‘basal cell urothelioma’.

Inverted urothelial papilloma: A review of diagnostic pitfalls and clinical management

“…3,5,7,11,16,18,19 The location within the urinary tract may also contribute to malignant potential, as ureteral IUP has a threefold greater rate of subsequent development of UC than IUP of the bladder. 7,19 However, given that 6% of IUPs are synchronously found with UC and the small size of ureteral biopsies, it is possible that the reported high rate of development of UC in the ureter is a reflection of sampling bias and under-diagnosis of UC with inverted growth. 9,12 Studies have shown rates of IUP recurrence from 1-7%, which occur 5-30 months following resection.…”

Atypia in inverted urothelial papillomas: Pathology and prognostic significance

“…Similarly, on reviewing the histological images provided in the case reports of Stower et al 7 and Uyama and Moriwaki, 8 we found that these images demonstrate what we believe are best regarded as inverted papillomas with atypia, rather than inverted papillomas with malignant changes. As in the case of Kimura et al, 6 in these 2 cases no known recurrence of these tumors was reported.…”

“…3,4 Although classically inverted papillomas have been described as having no cytological atypia, there have been scattered reports in the literature of inverted papillomas with atypical features. Kimura et al, 6 Stower et al, 7 and Uyama and Moriwaki 8 described cases of inverted papillomas with malignant changes. Notably, all 3 of these atypical lesions were located in the upper genitourinary system, which is a less frequent site of occurrence.…”

Inverted urothelial papillomas with foamy or vacuolated cytoplasm

“…Of these cases, a few are better classified as inverted papillomas with atypia, connoting lesions with merely focal cytologic atypia in otherwise classic inverted papillomas [11][12][13][14]. Conversely, most batypical inverted papillomasQ in the literature have exhibited exophytic papillary carcinoma components, large, rounded, nonanastomosing cellular nests, diffuse cytologic atypia, or high mitotic rates [4,[15][16][17][18][19][20][21].…”