Deep Penetrating Nevi

DPN Showing Wedge-Shaped Infiltrate
This is a subtle case of deep penetrating nevus (DPN) on low-power examination. There are, however, dermally located subtle nests and fascicles of melanocytes image. There is no junctional image component.

DPN: Inflamed With Melanophages
There is a lymphocytic infiltrate image that surrounds the lightly melanized fascicles and nests of melanocytes image. Note the melanophages image located deep in the reticular dermis.

Melanocytes Intervening Between Collagen Bundles
This power shows cords and smaller fascicles of melanocytes image that intervene between collagen bundles. This feature may be more prominent in plexiform spindle cell tumors. It can resemble a dermatofibroma as the melanocytes “trap” collagen bundles image.

Mild Cytological Atypia in DPN
High-power examination shows mild, focal nuclear pleomorphism and prominent nucleoli image. The remainder of nuclei are fusiform with smooth nuclear membranes and conspicuous nucleoli image. No mitoses were found in this example.



• Deep penetrating nevus (DPN)


• Plexiform spindle cell nevus


• Benign, uncommon variant of melanocytic nevus (likely blue nevus variant)
image Characterized by wedge-shaped or plexiform growth pattern

• Significant overlap with inverted type A nevus, but cytological atypia and low mitotic activity do not necessarily portend sinister outcome

• Clonal nevus may represent superficial variant of inverted type A nevus or DPN


Histological Variance

• Often associated with 2nd nevoid subtype, thereby overlapping with combined nevus

• Variant of melanocytic nevi with histologic features that may be alarming and can be mistaken for malignant melanoma



• Patients between 10-30 years


• Head (face) and neck, back (upper trunk), and proximal extremities


• Irregular dark brown to black papule or nodule measuring 0.2-1.0 cm in diameter
• Typically, they are darkly pigmented

• May show variegation in color, including shades of brown, blue, and black

image Can create initial clinical concern for malignant melanoma (29% of cases)

Natural History

• Lesions without cytological atypia and low mitotic activity show no local recurrences and no distant metastases
• Those with atypia and mitotic activity > 3/mm² can metastasize

• DPN-like borderline tumors can be associated with regional lymph node metastasis

image May exhibit potential for melanoma progression despite normal cytogenetic profile


• Surgical approaches
image When devoid of atypia, it is treated by simple excision

image Patients with DPN-like borderline tumors should be aggressively managed

– At least complete reexcision and consideration of sentinel node biopsy, regardless of cytogenetic data

image All atypical plexiform spindle cell melanocytic tumors should be completely excised with clear margins, and high-grade or potentially malignant lesions may require management as melanoma


• Patients with typical plexiform spindle cell melanocytic tumors do well
image i.e., without tumor recurrence or death in mean follow-up period of 3.9 years

• 1 patient with atypical typical plexiform spindle cell melanocytic tumor had sentinel lymph node involvement
image Patient was alive without recurrent disease at 1-year follow-up

• 3 patients with high-grade lesions developed lymph node involvement
image All 3 patients were alive with 2-4 years of follow-up

• Patients with DPN-like borderline tumors may show lymph node involvement (33%)
image Can rarely recur or metastasize

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Deep Penetrating Nevi

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