Female 18. Deeply pigmented lesion on trunk.?warty naevus?seborrhoeic keratosis?malignant melanoma. The best diagnosis is:

Female 18. Deeply pigmented lesion on trunk.?warty naevus?seborrhoeic keratosis?malignant melanoma. The best diagnosis is: A. deep penetrating naevus B. naevoid malignant melanoma C. pigment synthesising melanoma (pigmented epithelioid melanocytoma) D. cellular blue naevus

Female 18. Deeply pigmented lesion on trunk.

A. deep penetrating naevus (plexiform spindle cell naevus) M=F, mainly 10-30yrs, solitary, circumscribed 5-10mm, often domeshaped blue/black nodule face, upper trunk, proximal limbs. Clinically?benign naevi/melanoma/non-melanocytic, present for mean of 1.4yrs Barnhill plexiform pigmented spindle cell naevus. Most symmetrical, wedge-shaped, compound (60-85%) but little junctional grow down neurovascular bundles, adnexae & into arrector pili muscle.

A. deep penetrating naevus Occasional hras mutations Lack the GNAQ or GNA11 mutations of blue naevi

deep penetrating naevus histological features Epithelioid (larger than common acquired naevi but much cytoplasm) and spindle cells. Random mild to moderate nuclear pleomorphism Inflammation & melanophages in most Some have clear cell change intranuclear pseudoinclusions. Deep dermis often (some superficial only) occasionally subcutis

deep penetrating naevus histological features 9/30 common acquired naevus component (i.e. combined naevus) 13/30 some cause for concern i.e. asymmetry, atypia, inflammation, expansile advancing margin but: low mitoses 0.86-1.2/mm 2. often no papillary dermis involvement: clue to diagnosis.

deep penetrating naevus histological features:

deep penetrating naevus histological features

naevoid malignant melanoma: BSD 2015 Case 20 deep penetrating naevus differential diagnosis: in situ melanoma present, more atypia, more mitoses

deep penetrating naevus differential diagnosis: Magro CM, Abraham RM, Guo R, Li S, Wang X, Proper S, Crowson AN, Mihm M. Deep penetrating nevus-like borderline tumours: A unique subset of ambiguous tumours with malignant potential and normal cytogenetics. Eur J Dermatol. 2014. Sep-Oct;24(5):594-602. Hung T, Yang A, Mihm MC, Barnhill RL. The plexiform spindle cell nevus nevi and atypical variants: report of 128 cases. Human Pathology 2014 Dec;45(12):2369-78. Small subset of deep penetrating naevus-like lesions often >40 yrs more cytologic and architectural atypia More mitotic activity, >3/mm 2 Overlap with deep penetrating naevus and (plexiform) melanoma High incidence of regional lymph node disease (1 in 3) Consider sentinel node biopsy

deep penetrating naevus differential diagnosis: Pigment synthesising melanoma (animal type melanoma): dendritic atypical junctional component more atypia mitoses more pigmented.

deep penetrating naevus differential diagnosis: Cellular blue naevus: similar but dumbbell shape less junctional.

deep penetrating naevus references: References 1. Robson A, Morley-Quante M, Hempel H, McKee PH, Calonje E. Deep penetrating naevus: clinicopathological study of 31 cases with further delineation of histological features allowing distinction from other pigmented benign melanocytic lesions and melanoma. Histopathology. 2003 Dec;43(6):529-37. 2. Luzar B, Calonje E. Deep penetrating nevus: a review. Arch Pathol Lab Med. 2011 Mar;135(3):321-6. 3. Strazzula L, Senna MM, Yasuda M, Belazarian L. The deep penetrating nevus. J Am Acad Dermatol. 2014 Dec;71(6):1234-40. 4. Magro CM, Abraham RM, Guo R, Li S, Wang X, Proper S, Crowson AN, Mihm M. Deep penetrating nevus-like borderline tumours: A unique subset of ambiguous tumours with malignant potential and normal cytogenetics. Eur J Dermatol. 2014. Sep-Oct;24(5):594-602. 5. Hung T, Yang A, Mihm MC, Barnhill RL. The plexiform spindle cell nevus nevi and atypical variants: report of 128 cases. Human Pathology 2014 Dec;45(12):2369-78.