Mucinous Nevus With Fat: An Unusual Case Report and Literature Review

Coexistence of mucinous nevus and multiple collagenoma with unilateral, dermatomal, and multi segmental distribution

Connective tissue nevus is a hamartoma composed of excess amounts of one or several components of the dermis, such as collagen, elastin, and proteoglycans. This report introduces a 14-year-old girl with grouped flesh color papules and skin color nodules distributed unilaterally with a dermatomal pattern. These lesions involved more than one segment. Histopathology is the gold standard for diagnosing collagenoma and mucinous nevus. We reported the first case of mucinous nevus with multiple collagenoma that shows the specific clinical features.

Mucinous Nevus

Mucinous nevus is an uncommon entity classified as either a cutaneous mucinosis or a connective tissue nevus. The condition presents as grouped papules and coalescent plaques growing in a unilateral or zosteriform manner. The key histopathological feature is a band-like deposition of mucin in the superficial dermis. A 34-year-old male presented with grouped gray-brown papules and confluent plaques exhibiting a zosteriform distribution on the right side of the lower back. The lesions had commenced in childhood. Histological examination revealed mucin deposition in the papillary dermis. Thus, we diagnosed a mucinous nevus. To date, only a few reports of such nevi have been reported in the literature. Therefore we report a rare case of mucinous nevus.

[Mucinous nevus of late onset]

INTRODUCTION

Mucinous nevus is a rare disease characterized by mucin deposits in the dermis, with only 23 cases reported to date. It belongs to the connective tissue nevus family and is characterized by dermal mucin deposits. Two histological subtypes have been described: pure mucinous dermal nevus (connective tissue nevus of the proteoglycan [CTNP]) and combined mucinous nevus (combined CTNP) associating epidermal nevus with dermal mucin deposits. Lesions generally appear in childhood or early adulthood. We report herein the case of a 59-year-old man with a symptomatic lesion.

OBSERVATION

A 59-year-old man consulted for unilateral lesions occurring linearly along the Blaschko line on the right lower limb, composed of brown verrucous papules, which started at the age of 50. The patient complained of itching caused by friction from clothes. Histological examination of a papule highlighted an acanthotic epidermis, with elongation of rete ridges and mucin deposits in the dermis showing uptake of alcian blue stain. The clinicopathological analysis enabled diagnosis of combined CTNP. We treated this nevus by surgical dermabrasion and observed a slight and cosmetically acceptable scar.

DISCUSSION

To our knowledge, our patient is the oldest reported to date and the only one to have complained of symptoms. Our review of the literature highlights the importance of skin biopsy to guide aesthetic or symptomatic treatment. CO2 laser and dermabrasion are recommended for combined CTNP as they treat the epidermal component with low risk of secondary scarring. However, these techniques should be avoided in pure dermal CTNP, where surgical excision alone is acceptable in order to achieve optimal cosmetic results.