Bladder - Microcystic variant

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Bladder

Urothelial carcinoma - invasive

Microcystic variant

Reviewer: Rugvedita Parakh, M.D. (see Reviewers page)
Revised: 8 February 2013, last major update June 2010
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

Definition
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● Predominant features of urothelial carcinoma, but with prominent inter- or intracellular lumens and no true glands

Terminology
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● Considered equivalent to urothelial carcinoma with gland-like lumina by AFIP authors (Murphy: Tumors of the Kidney Bladder and Related Urinary Structures, AFIP Atlas of Tumor Pathology, Series 4, Vol 1, 2004, p 283), but WHO appears to make a minor distinction (Eble: Pathology and Genetics of Tumours of the Urinary System and Male Genital Organs, WHO 2004, p 99)

Etiology
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● Cyst-like structures may be due to ability of urothelium to form and line spaces (as occurs in bladder)
● May also be due to cell degeneration (based on presence of luminal debris and necrotic cells)

Clinical features
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● Uncommon variant associated with high stage and high grade tumors (Br J Urol 1997;79:722)
● Report as “urothelial carcinoma with microcystic differentiation”

Case reports
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● 56 year old men with microcystic histology in penile metastasis (Pathol Res Pract 2009;205:568, Pathol Oncol Res 2007;13:170)
● 80 year old man with microcystic tumor that also had gland-like lumina and signet-ring cell differentiation (Diagn Pathol 2008;3:36)

Micro description
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● Prominent intercellular or intracellular lumens / microcysts surrounded by neoplastic urothelial or squamous cells
● Lumens are usually empty, but may contain granular eosinophilic debris, necrotic cells or mucin
● Cysts vary in size, are round/oval, up to 2 mm; are lined by urothelium, flattened cells or low columnar cells, but not colonic epithelium or goblet cells (Am J Clin Pathol 1991;96:635)
● Cysts are infiltrative and may invade the muscularis propria
● Pattern resembles cystitis glandularis et cystica
● Also elongated, irregular branching spaces
● May rarely have neuroendocrine differentiation (Virchows Arch 2009;454:223)

Micro images
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Multicystic and papillary architecture

Lumens contain PAS+ material (hematoxylin-eosin)

Signet-ring cells present in walls of cysts (hematoxylin-eosin)

CK20+

CK7

Urothelial carcinoma with gland-like lumina (H&E and Alcian blue)

Urothelial carcinoma with gland-like lumina (H&E and mucicarmine)

Cysts vary in size and grow irregularly in the lamina propria

Small cyst with luminal bulls-eye secretion

Nodal metastasis has large, irregular and ramified cysts

Tumors of renal pelvis

Differential diagnosis
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● Adenocarcinoma: diffusely lined by goblet cells or intestinal cells, not flattened urothelial-like cells; usually deeply invasive, high grade
● Cystitis cystica / glandularis: glands in lamina propria lined by columnar, cuboidal or intestinal epithelium; no atypia, mitotic figures or necrosis
● Mucoid cytoplasmic inclusions: present in up to 37% of urothelial carcinomas, often high grade (Hum Pathol 1992;23:860)
● Müllerianosis: presence of 2 of 3 (endocervicosis, endometriosis or endosalpingiosis); no atypia, no mitotic figures
● Nephrogenic metaplasia / adenoma: small hollow tubules similar to mesonephric tubules, usually lined by single layer of bland cuboidal or hobnail cells, surrounding eosinophilic or basophilic secretions; typically not cystic, no/minimal atypia or mitotic figures; no true invasion
● Urothelial carcinoma with glandular differentiation: similar, but has true glands lined by goblet cells or colonic epithelium; is primarily a urothelial tumor, in contrast to adenocarcinoma
● Urothelial carcinoma, nested variant: may have focal tubular differentiation

End of Bladder > Urothelial carcinoma - invasive > Microcystic variant

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