Inverted Type A (Clonal) Nevi


ITAN Clinical
Clinically, an inverted type A nevus (ITAN) is image compared to other pigmented papules. ITAN has an eccentrically placed dark papule upon an evenly pigmented flat area. The lesional borders are sharp in contrast to dysplastic nevus. (Courtesy R. McClintok, MD.)



image
ITAN at Scanning Magnification
At scanning magnification, the nevus resembles an ordinary nevus with admixed melanophages image.

image
ITAN at Low Magnification
At low power, the more epithelioid nests are identified in the middermis toward the bottom of the lesion image. There is also a 2nd population of type B cells image, resembling lymphocytes at this power.

image
ITAN at Intermediate Magnification Showing Maturation
Under medium-power magnification, the type A nevus nests image are contrasted to the type B cells image. There is also a junctional component image.


TERMINOLOGY


Abbreviations




• Inverted type A nevus (ITAN)


Synonyms




• Clonal nevus (superficial)

• Deep penetrating nevus (deep seated)


Definitions




• Benign melanocytic nevus with inverted maturation of dermal melanocytes


CLINICAL ISSUES


Presentation




• Recent color change in otherwise benign preexisting nevus

• Usually thin brown papule with eccentric small focus of dark pigmentation within less pigmented macule


Treatment




• Surgical approaches
image Shave or simple excision is usually curative


Prognosis




• Excellent, no reported local recurrence or metastasis


IMAGING


General Features




• Dermoscopy shows regular and uniform brown globules with eccentric small blue-grey blotch


MICROSCOPIC


Histologic Features




• Collection of nests with distinctively epithelioid morphology, type A nevus cells
image Cells located at or near bottom of lesion

image Type A nevus cells are typically present in superficial dermis

– Location deep in reticular dermis gives its name, “inverted type A”

• May have variants or admixed with cell types
image Purely type A (epithelioid nevus cells)

image Type B (lymphoid nevus cells)

image Type C (spindled nevus cells)

image Dendritic blue cells

• Surrounded by numerous melanophages


Cytologic Features




• Nuclei of type A cells are round-to-plum/oval in shape with finely melanized cytoplasm

• Even chromatin with inconspicuous nucleoli

• Nuclear membrane is smooth

• Mitoses are absent to extremely rare

Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Inverted Type A (Clonal) Nevi
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