Tubulocystic Carcinoma

Satish K. Tickoo, MD

Danielle E. Westfall, MD

Victor E. Reuter, MD

Key Facts

Terminology

Tubulocystic carcinoma (TC) of kidney
- Well-circumscribed carcinoma with pure tubular and cystic architectural growth
- Cysts and tubules lined by single layer of atypical cells with abundant eosinophilic cytoplasm and variable “hobnailed” appearance

Clinical Issues

Uncommon; < 60 cases reported in literature
Considered potentially of low malignant behavior
Strong male preponderance; M:F = 7:1 or greater

Macroscopic Features

Well-circumscribed tumors with spongy “bubble wrap” appearance

Microscopic Pathology

Composed of small to intermediate-sized tubules admixed with cystically dilated tubules, dispersed evenly in frequently fibrotic stroma
Tubule and cyst lining composed of single layer of flat, “hobnail,” or cuboidal to columnar cells
Cellular stratification and papillations very focal and uncommon

Ancillary Tests

Majority are positive for CK7, CK19, parvalbumin, CD10, AMACR, and Ksp-cadherin

Top Differential Diagnoses

Collecting duct carcinoma with TC-like areas
Other adult renal epithelial tumors with predominant tubules and cysts

Gross photograph demonstrates a well-circumscribed tumor with a spongy cut surface and variable sized cysts, the typical gross appearance of a tubulocystic carcinoma.

A low-power view of tubulocystic carcinoma shows variably sized tubules and cysts, lined by a single layer of epithelium.

TERMINOLOGY

Abbreviations

Tubulocystic carcinoma (TC) of kidney

Definitions

Well-circumscribed renal cell carcinoma (RCC) with pure tubular and cystic architectural growth
- Cysts and tubules lined by single layer of atypical cells with abundant eosinophilic cytoplasm and variable “hobnail” appearance

ETIOLOGY/PATHOGENESIS

Historic Perspective

Initially described in 1956 by Masson and designated as Bellinien epithelioma
Examples illustrated in 3rd AFIP fascicle as collecting duct carcinoma (CDC), subsequently designated low-grade CDC
- This group also contained some cases now regarded as mucinous tubular and spindle cell carcinoma
Recently considered as distinct entity
- Exact relationship with collecting duct carcinoma still unclear
  - Particularly because areas with TC-like morphology are occasionally observed in otherwise typical CDCs

Molecular Abnormalities

Unique molecular signature distinct from clear cell and chromophobe RCC reported in Affymetrix X3P oligonucleotide microanalysis
- Overexpression of genes related to
  - Amino acid metabolism
  - Cell cycle
- Underexpression of many biopolymer metabolism genes
Based on a single case, using clustering analysis, molecular signature also reported to be closely related to papillary RCC
No published large molecular study analyzing relationship to, or distinction from, collecting duct carcinoma

CLINICAL ISSUES

Epidemiology

Incidence
- Uncommon; < 60 cases reported in literature
Age
- 34-94 years (mean: 60 years)
Gender
- Strong male preponderance; M:F = 7:1 or greater

Presentation

Majority asymptomatic, incidentally discovered radiologically; occasionally abdominal fullness, flank pain, or hematuria

Treatment

Usually amenable to surgical treatment due to low tumor stage at presentation
Single reported case of metastatic disease treated with multikinase inhibitor sunitinib as adjuvant with documented clinical and radiographic regression

Prognosis