Case prepared by Dr Viren Vaghasiya and Dr Jitendra Nasit
Cellular Blue nevus
Grossly the lesion is circumscribed bluish-black nodule of around 15mm. The cut surface shows a homogenous brownish-black area.
Histopathology:
– Relatively circumscribed lobular nested and dumbbell-shaped dermal-based lesion consisting of a melanocytic cells proliferation.
– The neoplasm shows two characteristics features: 1. fascicles and nesting/alveolar pattern of bland-looking spindled to ovoid/epithelioid amelanotic melanocytes with clear cytoplasm and small distinct nucleoli; 2. pigmented bipolar spindle dendritic melanocytes in a dense fibro-collagenised background of the dermis.
– The border/base of the lesion has a pushing interface with subcutaneous fat involvement and entrapment of adnexal structures.
– The epidermis is unremarkable, and Junctional activity is not seen.
– Only single mitosis is found in the entire lesion (not shown here). There are no marked cytological atypia, necrosis, or frequent/atypical mitoses.
Practical points of Pathoclinis:
- Blue nevus (a benign melanocytic lesion) has two variants: common (dendritic) blue nevus and cellular blue nevus.
- Cellular blue nevus typically occurs in young adults with a slight female predilection. Buttocks and extremities are common sites for cellular blue nevus but can occur in a wide variety of sites.
- The cellular blue nevus is relatively larger (1-3 cm in size) than the common blue nevus. It has more cellularity, appreciable mitotic rate, intense pigmented melanocytes, and subcutaneous involvement with well-defined border.
- Intermediate/worrisome features like ulceration, deep infiltration, cytological atypia, sheet-like growth, mitoses (< 2/mm2), necrosis, and regional nodal involvement (benign metastatizing blue nevus) in cellular blue nevus (atypical cellular blue nevus), create a significant diagnostic problem and easily mimic melanoma. In such doubtful instances, the complete excision with free margins and follow-up is justified.
- Features suggestive of malignancy are: progressive growth, multi-nodular surface, larger size >3 cm, scalp location, mitoses (> 2/mm2), atypical mitoses, necrosis, junctional melanocytic component with an intraepidermal pagetoid spread
- Local recurrences of cellular blue nevus can occur if incompletely excised.
- Cellular blue nevus with a gain of chromosome 6p and loss of chromosome 6q should undergo careful clinical follow-up as these aberrations are commonly seen in melanoma.
Resources for learning and reference:
- Daltro LR, Yaegashi LB, Freitas RA, Fantini BC, Souza CD. Atypical cellular blue nevus or malignant blue nevus? An Bras Dermatol. 2017 Jan-Feb;92(1):110-112. doi: 10.1590/abd1806-4841.20174502. PMID: 28225968; PMCID: PMC5312190.
- Youtubevideo:https://www.youtube.com/watch?v=rLY_rm8H7Vo&ab_channel=JeradGardner%2CMD
- https://www.pathologyoutlines.com/topic/skintumormelanocyticbluenevus.html
