CYSLTR2-mutant Cutaneous Melanocytic Neoplasms Frequently Simulate “Pigmented Epithelioid Melanocytoma,” Expanding the Morphologic Spectrum of Blue Tumors: A Clinicopathologic Study of 7 Cases.

CYSLTR2-mutant Cutaneous Melanocytic Neoplasms Frequently Simulate “Pigmented Epithelioid Melanocytoma,” Expanding the Morphologic Spectrum of Blue Tumors: A Clinicopathologic Study of 7 Cases.

Publication date: May 31, 2019

Recurrent activating Gαq mutations in the spectrum of blue nevi have been well studied. However, the clinicopathologic characteristics of the recently described CYSLTR2-mutant and PLCB4-mutant blue nevi remain limited, owing to their rarity. Herein, we present 7 CYSLTR2-mutant melanocytic neoplasms, including 1 cellular blue nevus, 4 atypical cellular blue nevi, and 2 blue nevus-like melanomas. They occurred on the scalp, breast, flank, forearm, thigh, leg, and ankle of 3 male patients and 4 female patients, with a median age of 43 (25 to 81) years at diagnosis. Five exhibited an exophytic growth, and 6 were heavily pigmented. A fascicular arrangement of medium to large spindle melanocytes was seen in 6 cases, but epithelioid cytology was present in only 2 cases, one of them being focal. A junctional component was present in 3 cases. Immunoreactivity for HMB45 was diffusely present, except in 1 cellular blue nevus. BAP1 nuclear immunoexpression was lost in 1 melanoma case. A canonical CYSLTR2 L129Q hotspot mutation was present in all cases. Altogether, these histopathologic findings suggest that CYSLTR2-mutant melanocytic blue neoplasms frequently exhibit a heavily pigmented exophytic tumor with a silhouette resembling “pigmented epithelioid melanocytoma” rather than usual cellular blue nevus. Moreover, most of these tumors were not clinically recognized as blue nevi and not located in the classic topography of cellular blue nevus aside from the scalp. However, a fascicular arrangement of medium to large-sized spindled melanocytes, as well as a lack of epithelioid or nevoid melanocytes, could be potential diagnostic clues to morphologically distinguish CYSLTR2-mutant tumors from “pigmented epithelioid melanocytoma.”

Goto, K., Pissaloux, D., Paindavoine, S., Tirode, F., and de la Fouchardi`ere, A. CYSLTR2-mutant Cutaneous Melanocytic Neoplasms Frequently Simulate “Pigmented Epithelioid Melanocytoma,” Expanding the Morphologic Spectrum of Blue Tumors: A Clinicopathologic Study of 7 Cases. 22858. 2019 Am J Surg Pathol.

Concepts Keywords
Breast Melanoma
Cytology Cellular blue nevus
Epithelioid Spitz nevus
Forearm Benign neoplasms
Gq Rare diseases
Histopathologic HMB-45
Hotspot Epithelioid
Melanocytes Melanoma
Melanoma Blue nevus
Melanomas Integumentary system
Morphologically Dermatology
Mutant Organ systems
Mutation Melanomas
Neoplasms Tumors
Nevi
Scalp
Silhouette
Spectrum
Spindle
Thigh
Topography
Tumor

Semantics

Type Source Name
pathway BSID Melanoma
disease DOID melanoma
gene UNIPROT MAGI1
gene UNIPROT BAP1
gene UNIPROT RNF2
gene UNIPROT LARGE1
disease MESH growth
disease MESH diagnosis
disease MESH melanomas
gene UNIPROT PLCB4
disease MESH blue nevi
disease MESH Neoplasms
gene UNIPROT CYSLTR2

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