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Background
Ocular melanomas are a different disease than its cutaneous counterpart. Uveal (choroidal) melanomas are the most common site comprising 85% of cases. Other sites include: ciliary body, iris, and conjunctiva.
OUTLINE
HISTOLOGICAL TYPES CHARACTERIZATION General Trans Am Acad Ophthalmol Otolaryngol 1931;26:131 Cohesive with poorly defined borders and folded nuclei Larger than A cells with prominent nucleoli rather than nuclear folds Palisaded arrangement of spindle B cells Distinct cell borders with large nuclei and prominent nucleoli VARIANTS 86% composed of mixed spindled and epithelioid cells
9% spindle cells
5% epithelioid cellsPredominately low grade spindle A cells VASCULOGENIC MIMICRY
- Distinguishing fibrovascular septa from vasculogenic mimicry patterns.
Lin AY, Maniotis AJ, Valyi-Nagy K, Majumdar D, Setty S, Kadkol S, Leach L, Pe'er J, Folberg R.
Department of Pathology, University of Illinois at Chicago, IL 60612, USA.
Arch Pathol Lab Med. 2005 Jul;129(7):884-92. Abstract quote
CONTEXT: Molecular analyses indicate that periodic acid-Schiff (PAS)-positive (laminin-rich) patterns in melanomas are generated by invasive tumor cells by vasculogenic mimicry. Some observers, however, consider these patterns to be fibrovascular septa, generated by a stromal host response.
OBJECTIVE: To delineate differences between vasculogenic mimicry patterns and fibrovascular septa in primary uveal melanomas.
DESIGN: Frequency distributions, associations with outcome, and thicknesses of trichrome-positive and PAS-positive looping patterns were determined in 234 primary uveal melanomas. Sequential sections of 13 additional primary uveal melanomas that contained PAS-positive/trichrome-negative looping patterns were stained for type I and type IV collagens, laminin, and fibronectin. Real-time quantitative polymerase chain reaction was performed on RNA from cultured uveal melanoma cells for the expression of COL1A1, COL4A2, and fibronectin.
RESULTS: Trichrome-positive loops were encountered less frequently than PAS-positive loops (10% vs 56%, respectively). Death from metastatic melanoma was strongly associated with PAS-positive (P < .001) but not with trichrome-positive (P = .57) loops. Trichrome-positive loops were significantly thicker than PAS-positive loops (P < .001). The PAS-positive patterns stained positive for laminin, type I and type IV collagens, and fibronectin. Type I collagen was detected within melanoma cells and focally within some PAS-positive patterns. Real-time quantitative polymerase chain reaction revealed 3-fold, 25-fold, and 97-fold increases, respectively, in expression of COL4A2, fibronectin, and COL1A1 by invasive pattern-forming primary melanoma cells compared with poorly invasive non-pattern-forming cells.
CONCLUSIONS: Fibrovascular septa are rare and prognostically insignificant in uveal melanomas, whereas vasculogenic mimicry patterns are associated with increased mortality. Type I collagen, seen focally in some vasculogenic mimicry patterns, may be synthesized by tumor cells, independent of a host stromal response.
Vascular channel formation by human melanoma cells in vivo and in vitro: vasculogenic mimicry.
Maniotis AJ, Folberg R, Hess A, Seftor EA, Gardner LM, Pe'er J, Trent JM, Meltzer PS, Hendrix MJ.
Department of Anatomy, University of Iowa Cancer Center, University of Iowa College of Medicine, Iowa City, USA.
Am J Pathol. 1999 Sep;155(3):739-52 Abstract quote.
Tissue sections from aggressive human intraocular (uveal) and metastatic cutaneous melanomas generally lack evidence of significant necrosis and contain patterned networks of interconnected loops of extracellular matrix. The matrix that forms these loops or networks may be solid or hollow.
Red blood cells have been detected within the hollow channel components of this patterned matrix histologically, and these vascular channel networks have been detected in human tumors angiographically. Endothelial cells were not identified within these matrix-embedded channels by light microscopy, by transmission electron microscopy, or by using an immunohistochemical panel of endothelial cell markers (Factor VIII-related antigen, Ulex, CD31, CD34, and KDR[Flk-1]). Highly invasive primary and metastatic human melanoma cells formed patterned solid and hollow matrix channels (seen in tissue sections of aggressive primary and metastatic human melanomas) in three-dimensional cultures containing Matrigel or dilute Type I collagen, without endothelial cells or fibroblasts. These tumor cell-generated patterned channels conducted dye, highlighting looping patterns visualized angiographically in human tumors. Neither normal melanocytes nor poorly invasive melanoma cells generated these patterned channels in vitro under identical culture conditions, even after the addition of conditioned medium from metastatic pattern-forming melanoma cells, soluble growth factors, or regimes of hypoxia. Highly invasive and metastatic human melanoma cells, but not poorly invasive melanoma cells, contracted and remodeled floating hydrated gels, providing a biomechanical explanation for the generation of microvessels in vitro. cDNA microarray analysis of highly invasive versus poorly invasive melanoma tumor cells confirmed a genetic reversion to a pluripotent embryonic-like genotype in the highly aggressive melanoma cells.
These observations strongly suggest that aggressive melanoma cells may generate vascular channels that facilitate tumor perfusion independent of tumor angiogenesis.
DIFFERENTIAL DIAGNOSIS KEY DIFFERENTIATING FEATURES PRIMARY ACQUIRED MELANOSIS Hum Pathol 1985;16:136
Divided into cases without atypia and with atypia
Atypical lesions are considered premalignant and 45% progress to melanoma
*Department of Pathology, Massachusetts General Hospital Harvard Medical School daggerDepartment of Ophthalmology, Massachusetts Eye and Ear Infirmary Harvard Medical School, Boston, MA.
The current World Health Organization classification of conjunctival melanocytic proliferations divides them into conjunctival nevi and invasive melanoma but, in contrast to other anatomic sites, does not recognize melanoma in situ. All atypical intraepithelial conjunctival proliferations are included in a heterogeneous category designated as primary acquired melanosis (PAM) with atypia.
We performed clinicopathologic analysis of 29 cases of PAM with atypia. On the basis of histologic features and frequency of association with invasive melanoma and metastases, we were able to divide our cases into 2 histologic groups. The low-risk group (13 cases) included lesions composed of small to medium size melanocytes with high nuclear to cytoplasmic ratio and small to medium size hyperchromatic nuclei devoid of nucleoli showing predominantly single cell lentiginous growth pattern. Invasive melanoma occurred in only 2 cases from this group. None of these lesions metastasized. The second, high-risk group (16 cases), showed increased frequency of association with invasive melanoma (15/16 cases, 94%) and metastases (4/16 cases, 25%).
These lesions were more heterogeneous architecturally but were all composed of melanocytes showing various degrees of epithelioid features such as abundant cytoplasm, vesicular nuclei, or prominent nucleoli. In 4 cases discrete areas showing high-risk and low-risk features were identified. All 4 lesions were associated with invasion.
Our findings offer a practical approach for prognostically useful subclassification of PAM with atypia, which emphasizes cytologic features of intraepithelial conjunctival melanocytic proliferation.
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Sternberg S. Diagnostic Surgical Pathology. Fourth Edition. Lipincott Williams and Wilkins 2004.
Robbins Pathologic Basis of Disease. Seventh Edition. WB Saunders 2005.
DeMay RM. The Art and Science of Cytopathology. Volume 1 and 2. ASCP Press. 1996.
Weedon D. Weedon's Skin Pathology Second Edition. Churchill Livingstone. 2002
Fitzpatrick's Dermatology in General Medicine. 6th Edition. McGraw-Hill. 2003.
Weiss SW and Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors. Fourth Edition. Mosby 2001.
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Last Updated February 2, 2010
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