Kidney tumor

• Uncommon multilocular cystic tumor without a grossly appreciable solid component
• Classified as part of mixed epithelial and stromal tumor (MEST) family with MEST at opposite end of spectrum, by the 2016 World Health Organization (WHO) Classification

• Mainly occurs in adult women
• Well circumscribed, multicystic tumors with no apparent solid component
  • Versus MEST - variable solid and cystic components
• Noncommunicating cysts lined by single layer epithelium separated by septa with hypocellular fibrous to hypercellular spindle cell stroma
• Most benign but very rare local recurrence and malignant transformation
• Stromal cells typically positive for ER / PR

• M:F = 1:8 (Semin Diagn Pathol 1998;15:2, Arch Pathol Lab Med 2004;128:1404, Am J Surg Pathol 2007;31:489, Am J Surg Pathol 2016;40:1591)
• Age, peak incidence 50 - 60 years (Semin Diagn Pathol 1998;15:2, Am J Surg Pathol 2016;40:1591)

• Possible role of hormones in pathogenesis (Am J Surg Pathol 2007;31:489)

• Often incidentally found
• Others present with abdominal / flank pain, hematuria, urinary tract infection, palpable mass (Urology 2008;71:1142)

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• 48 year old woman with adult cystic nephroma (Turk J Urol 2018;44:373)
• 57 year old woman with local recurrence of adult cystic nephroma (Int J Urol 2004;11:329)
• 59 year old woman with ureteral invagination of multilocular cystic nephroma (adult cystic nephroma) (Int J Clin Exp Pathol 2014;7:5271)
• 65 year old woman with cystic renal cell carcinoma arising from multilocular cystic nephroma (adult cystic nephroma) (Int Braz J Urol 2006;32:187)
• 66 year old man with adult cystic nephroma (Rare Tumors 2015;7:5860)

• Nephron sparing surgery whenever feasible

• Unilateral but rarely bilateral (Urology 2008;71:1142, Am J Surg Pathol 2009;33:72)
• Well circumscribed, multilocular cystic mass
• Median size: 6.8 cm (Am J Surg Pathol 2016;40:1591)
• Noncommunicating thin walled cysts of varying sizes
  • Smooth and glistening linings
  • Filled with serous to serosanguinous fluid

Contributed by Bonnie Choy, M.D.

• Many with at least a partial pseudocapsule
• Entirely composed of cysts separated by septa (Semin Diagn Pathol 1998;15:2, Arch Pathol Lab Med 2004;128:1404, Am J Surg Pathol 2007;31:489, Eur Urol 2008;54:1237, Am J Surg Pathol 2016;40:1591)
• Stroma:
  • Hypocellular to hypercellular
  • Collagenous and fibrous to edematous and myxoid
  • Areas of hyalinized stroma with contours resembling ovarian corpora albicantia
  • Spindle cells; closely packed areas resemble ovarian stroma
  • Cellular foci embedded with epithelial elements ranging from handful of cells with no lumen to tiny cysts with pinpoint lumens and to slightly larger cysts
  • Steroidogenic cells: small clusters of polygonal cells with amphophilic cytoplasm and round nuclei, frequently around epithelial component
  • Calcifications, multinucleated giant cells, foamy or hemosiderin laden macrophages and focal chronic inflammation
• Epithelium:
  • Cells lining cysts
  • Mostly arranged in single layer with various morphology: flat, cuboidal, hobnail, clear cell
  • Rarely, foci of blunt and delicate papillae or foci of multiple layers of epithelium
• Minimal cytologic atypia
• Rare necrosis, no mitosis

Contributed by Bonnie Choy, M.D.

Images hosted on other servers:

• Stroma:
  • SMA: strong and diffuse, 95% (Am J Surg Pathol 2016;40:1591, Arch Pathol Lab Med 2004;128:1404, Arch Pathol Lab Med 2006;130:80)
  • Desmin and caldesmon: more variable, 42% and 60%, respectively (Am J Surg Pathol 2016;40:1591, Arch Pathol Lab Med 2004;128:1404)
  • ER and PR, 50% and 95%, respectively (Am J Surg Pathol 2016;40:1591, Arch Pathol Lab Med 2004;128:1404, Arch Pathol Lab Med 2006;130:80, Am J Surg Pathol 2007;31:489)
  • CD10: mainly in spindle cells around epithelial elements, 81% (Am J Surg Pathol 2016;40:1591, Arch Pathol Lab Med 2004;128:1404, Am J Surg Pathol 2007;31:489)
  • FOXL2: in ovarian type stroma, 90% (Hum Pathol 2014;45:1010)
• Epithelium:
  • Cytokeratins, including CK7 (Arch Pathol Lab Med 2004;128:1404, Arch Pathol Lab Med 2006;130:80)
  • PAX8, 100% (Am J Surg Pathol 2016;40:1591)
  • CD10: focal (Arch Pathol Lab Med 2004;128:1404, Arch Pathol Lab Med 2006;130:80, Am J Surg Pathol 2016;40:1591)

• Left kidney, mass, partial nephrectomy:
  • Adult cystic nephroma, measuring 6.5 cm in greatest dimension (see comment)
  • Surgical margins, negative for tumor
  • Comment: The sections show a well circumscribed tumor composed of multiple cysts lined by flattened or cuboidal epithelium. Immunohistochemistry was performed to show the septal stroma is positive for ER and PR. The morphologic and immunohistochemical findings support the diagnosis of adult cystic nephroma.

A 6 cm predominantly well circumscribed, multicystic mass was incidentally found in a 55 year old woman. Sections of the partial nephrectomy showed the above histologic features. The stromal component is positive for ER and PR (shown above). What is the likely diagnosis?

1. Adult cystic nephroma
2. Angiomyolipoma with epithelial cysts
3. Cystic partially differentiated nephroblastoma
4. Multilocular cystic neoplasm of low malignant potential

A. Adult cystic nephroma. Adult cystic nephroma is a well circumscribed, predominantly cystic mass. Angiomyolipoma with epithelial cysts shares overlapping histologic features but the stroma is immunopositive for melanocytic markers. Cystic partially differentiated nephroblastoma typically occurs in children. Multilocular cystic neoplasm of low malignant potential has nests of tumor cells with abundant clear cytoplasm and small nuclei without prominent nucleoli. None of the above choices, except for adult cystic nephroma, demonstrate immunoreactivity for ER and PR.

Comment Here

Reference: Adult cystic nephroma

Which of the following is true about adult cystic nephroma?

1. Frequent DICER1 gene mutations
2. Most are bilateral tumors
3. Often indolent with very rare malignant transformation
4. Typically occur in children with strong male predominance

C. Often indolent with very rare malignant transformation. Adult cystic nephroma is considered benign with very rare reports of local recurrence or malignant transformation. The tumors usually present as unilateral tumors and typically seen in adult women. Unlike pediatric cystic nephroma, neither adult cystic nephroma nor mixed epithelial and stromal tumor has been found to have DICER1 mutations.

Comment Here

Reference: Adult cystic nephroma