Melanocytic aggregates with unique morphology associated with regression of basal cell carcinoma

Lichenoid dermatoses with pseudomelanocytic nests vs inflamed melanoma in situ: A comparative study

AIMS

Pseudomelanocytic nests or "pseudonests" arising in lichenoid dermatoses can be a diagnostic pitfall for melanoma in situ (MIS), especially on sun-damaged skin. We sought to evaluate histopathological features that may be helpful in distinguishing this benign process from inflamed MIS.

METHODS

Ten biopsy specimens containing pseudomelanocytic nests within lichenoid dermatoses and twenty cases of inflamed MIS were retrospectively reviewed. Cases with pseudomelanocytic nests represented either a rash (n = 6) or a discrete non-melanocytic lesion, such as lichenoid keratosis (n = 4).

RESULTS

All cases with pseudomelanocytic nests showed nests of microphthalmia-associated transcription factor-positive cells at the dermoepidermal junction (DEJ) with interface changes and lichenoid inflammation. Pagetoid scatter, confluence of solitary melanocytes at the DEJ and significant cytologic atypia was not seen in any of these cases. In contrast, all cases of inflamed MIS demonstrated confluence of single melanocytes at the DEJ with cytologic atypia (P < 0.001) and 18/20 cases showed pagetoid scatter of melanocytes (P = 0.001).

CONCLUSIONS

Our results show that, of the different histopathological features assessed, confluent growth and pagetoid scatter of atypical melanocytes were seen in most cases of inflamed MIS but were absent in all cases with pseudomelanocytic nests. Therefore, in addition to clinicopathological correlation, these features may be useful in differentiating pseudomelanocytic nests arising in lichenoid dermatoses from inflamed MIS.

Efficacy of Vismodegib in pigmented basal cell carcinoma: Appearances are deceiving

Basal cell carcinoma (BCC) is the most common skin cancer in humans. Pigmented basal cell carcinoma (pBCC) is a rare variant of BCC. Vismodegib, was the first drug to be approved for the treatment of locally advanced (laBCCs) or metastatic basal cell carcinoma. The aim of this study was to evaluate the efficacy of Vismodegib in patients with pBCCs. We retrospectively analyzed patients receiving Vismodegib as treatment for laBCCs presenting also various pBCCs. After 6 months of treatment, we performed excisional biopsies of pBCCs, that apparently at clinical and dermoscopic assessment did not respond to therapy. A total of nine patients were assessed. After 6 months of treatment, locally advanced target BCCs showed complete remission in four out of nine patients (44.4%), four patients (44.4%) were considered in partial remission and one patient (11%) showed no response to treatment. On the contrary, all the pBCCs showed both clinically and dermoscopically resistance to treatment. Therefore, clinically persistent pBCCs were surgically removed in three patients. Histology showed a complete elimination of the neoplastic cells together with features of previous regression. Our findings indicate that the efficacy of Vismodegib is higher than that documented by clinical or even dermatoscopic observation alone.