Melanocytes Containing Large Nuclei and Abundant Pale Cytoplasm in Melanocytic Nevi
We read with interest the authoritative study by Fernandez-Flores and Cassarino1 on unusual histopathologic patterns in melanocytic nevi, which was published in the March issue of the journal. In this study, the authors reviewed the cellular changes, the architectural patterns, the changes imitating a nonmelanocytic component, the changes in the extracellular matrix, and the proliferative nodules in congenital melanocytic (CM) nevi. Within the cellular changes, the authors included the presence of clear cells, oncocytic, and granular cell changes, and eosinophilic cytoplasmic inclusion bodies. However, a cellular change that the authors did not mention was the presence of melanocytes containing large nuclei and abundant pale cytoplasm sometimes with dusty melanin granules large nucleus pale cytoplasm melanocyte (LNPCM) in some melanocytic nevi.2,3 These melanocytes exhibit large vesicular nuclei without prominent nucleoli and may appear individually or in groups. LNPCM have been reported as a characteristic feature of special-site nevi in melanocytic nevi on and around the ear2 and nevi of the scalp.3 In these locations, LNPCM may be seen as a junctional component of the nevus. Furthermore, these cells may also be present as a junctional melanocytic hyperplasia associated with intradermal nevi.4 Okamura et al4 observed this melanocytic proliferation in 6.2% of intradermal nevi and named it benign atypical junctional melanocytic hyperplasia. These authors warned of the possibility of interpreting the lesion as a melanoma in situ.
We have found these characteristic melanocytes located in the dermal component of 11.1% of CM nevi (5 cases of 45 congenital melanocytic nevus, unpublished observation). We report herein a case of CM nevus showing prominent LNPCM in the dermal component of the compound nevus.
A 13-year-old girl had a pigmented melanocytic nevus on her right thigh since birth. The lesion increased in size after the growth of the patient. A family history for CM nevi was negative.
On physical examination, the patient presented a single pigmented plaque located on the outer lower third of the right thigh. The plaque was verrucous, showed presence of hairs, and did not extend beyond that anatomic area. It showed small discrete nodular projections. The maximum diameter was 10.5 cm (Fig. 1). A 4-mm punch biopsy was taken from the edge of the lesion.
Microscopically, the pattern of the lesion was that of a compound melanocytic nevus. The epidermis showed hyperplastic, elongated epidermal rete pegs with hyperpigmentation and increased density of melanocytes along the basal layer. Occasional small junctional nests were present. The dermal component was constituted by small cuboidal melanocytes with scant, eosinophilic cytoplasm, and uniform nuclei forming separated or confluent nests in papillary and reticular dermis. Ensheathment of the hair follicles, involvement of arrector pili muscles, and single-file interstitial permeation of collagen by these melanocytes were evident. Cellularity decreased from top to bottom. Maturation in the dermis was present. Aggregates and single units of large pale melanocytes were scattered in the dermis. These cells were round or oval with abundant pale cytoplasm and uniform staining, large, round, or oval basophilic, or vesicular nuclei with visible nucleoli (Fig. 2). Their cytoplasms sometimes showed pulverulent melanin pigment (Fig. 3). Groups of these cells were also observed near small dermal nerves and vessels. Occasional junctional LNPCM were also observed. Mitoses were not found. The density of hair follicles was increased. There was a slight lymphocytic superficial infiltrate.
Junctional, large uniform melanocytes with abundant pale cytoplasm, and large vesicular nuclei without prominent nucleoli or LNPCM have been reported as a characteristic feature of special-site nevi.2,3 Lazova et al2 reported these cells in 62% of nevi on and around the ear and Fisher et al in 96% of scalp melanocytic nevi.